Sorry. It was a novel and I don't recall the title or author. I was just quite taken with it at the time and had thought a lot about fiction authors sometimes channeling truths unawares.
Sorry. It was a novel and I don't recall the title or author. I was just quite taken with it at the time and had thought a lot about fiction authors sometimes channeling truths unawares.
Hi Gnosis Sophia! The very same thing happened to me...and I have been digging again on the story of the trees and the book where she originally read the story...
Perhaps you would like to join the quest?
Thank you for the offer
Must say I was very glad for Lainey’s input to your question because while it was also my first impulse, that Amazon had the published date as 2014 made me refrain...
A decision that made me feel a bit of dill today on learning that ‘Tara Janzen’ was a pen name...
Q: Now, on a couple of occasions we have talked about trees. You have said that the trees would lead me to an answer. Then you made remarks about beechnut, and oaks, and beech and bloodlines and family trees and the Nordic Covenant. Basically, I asked about this Nordic Covenant and you said that I would find the answer, that the trees would lead me to it. I asked what literary source I should go to to find the least distorted source of information. You answered "trees" again. Then, you pointed out the leaves of the trees on this book. Later, when I read the book that was all about trees, it said that there was a need for someone of a certain bloodline to come along and free the dragon spawn. "None other than she can bring the pryf, or soul, up from the deep, no matter how they may make the serpents squirm. If she can hold her place in the gates of time." You answered me "You cannot see?" It also says that this person with this certain bloodline has the duty of creating a bridge between man and the gods to open the doorways of time. You said to me that these things had explanations that were readily apparent. Then, when I asked the question about this book and all the trees in it, that this was a clue given so that I would notice the things in this particular book, you said "certainly."
Now, having gone through all the shamanic stuff, all the information about the world tree, the world axis, and your remarks about building a staircase, which is another variation on the world axis or world tree, and having some kind of mission, and the mission being piercing the spider, which relates again to the world axis and the world tree, which one climbs one step at a time. Then, you talked about Jack and the Beanstalk, which is another example of the world tree. Over and over again we are having all these representations of trees which basically has something to do with some sort of destined action, and it is almost as though you are hinting that some person has to be physically tuned as a transducer of some sort to "stand in the gates of time," for the rest of humanity. Then, you made the remark recently about lodestar. Well, there might have been a time in my life when I might have thought that it was me who could do something like that. And, if I ever did, maybe it was even ego thinking. However, I am getting a little old for that sort of thing, so I don't really think that it is my role. But, I do think that there is somebody in the world whose role that is, and I would like to know if that is somebody we are supposed to be looking for, or that we are going to find this person?
A: Perhaps you shall find, or perhaps they will find you!
September 23, 2000
Q: Liquids from where to where?
A: What is your sense?
Q: Well, what liquids?
A: Time for your input.
Q: Do some of these...
A: No. Not alright: we asked you a question! [ed.:]
Q: Okay. Truncated flow of liquids. I'm not even sure what that means. (A) Maybe something was flowing and something cut it off and stopped it and it cannot be developed. It means that something was cut. (L) Does truncated flow mean a flow of liquid that has been stopped?
A: Yes. Because of design alteration!
Q: Is this liquid that has been truncated a chemical transmitter?
Q: And would this chemical transmitter, if it were allowed to flow, cause significant alterations in other segments of the DNA?
Q: So, there is a segment of code that is in there, that is deliberately inserted, to truncate this flow of liquid, which is a chemical transmitter, or neuropeptide, which would unlock significant portions of our DNA?
A: Close Biogenetic engineering.
Q: I assume that this was truncated by the Lizzies and cohorts?
A: Close, but more likely Orion STS designers.
Q: Okay, can you tell us what this specific liquid or transmitter [is that] was truncated?
A: Think of the most efficient conductor of chemical compounds for low wave frequency charge.
Q: (A) Well, gold is one... (L) Acetylcholine?
Q: (L) Water?
A: Closer. It is a naturally bonding combination.
Q: (L) Well, I'll have to research it. The fact is, we've got 3 billion base pairs... do some of these so-called segments of "junk DNA," if they were activated, would they instruct chromosomal replication to take place with more than 23 pairs as a result?
A: In part.
Q: Is there anything we can do in terms of activities or...
A: No. Biogenetic engineering.
NotedI wonder what about zinc or rather zinc oxide. It has some link to nicotinamide uptake and has an effect on fear regulation somehow.
Here are a couple of references
Neuronal nicotinic acetylcholine receptors are modulated by zinc./
E Vazquez-Gomez., J, Garcia-Columba
Zinc transporter 3 is involved in learned fear and extinction, but not in innate fear
Guillaume Martel,Charles Hevi,Olivia Friebely, Trevor Baybutt and Gleb P. Shumyatsky1
Zinc oxide is also a salt
That's reproduced in full because I thought it was worth the read. The website also has a few worthwhile graphics for overall functions, metabolism, and regulation. It's very important that the levels are tightly controlled, and the feedback by which this is achieved is claimed to be unique.Polyamines: Regulation and molecular functions
Polyamines are low molecular weight aliphatic polycations, highly charged and ubiquitously present in all living cells. Interest has been increasing during the last 30 years in the naturally abundant polyamines putrescine (diamine), spermidine (triamine) and spermine (tetramine), which were demonstrated to be involved in a large number of cellular processes. For example, polyamines participate in modulation of chromatin structure, gene transcription and translation, DNA stabilization, signal transduction, cell growth and proliferation, migration, membrane stability, functioning of ion channels and receptor-ligand interactions Polyamines seem to exert their role through ionic interactions, owing to their unique structural feature of regularly spaced positive charges.
Inside the cell polyamines are present in nearly millimolar concentrations. There is equilibrium between polyamines that are bound to different polyanionic molecules (mainly DNA and RNA) and free polyamines. The free polyamine pool represents 7-10% of the total cellular polyamine content. Only the free intracellular polyamines are available for immediate cellular needsand therefore are subject to strict regulation. Polyamines are maintained within very narrow range because decrease in their concentrations inhibits cell proliferation while excess appears to be toxic. Therefore, the free polyamine pools are regulated in a very fast, sensitive and precise manner. This regulation is achieved at four levels: de novo synthesis, interconversion, terminal degradation and transport.
Polyamine synthesis occurs in the cytoplasm of cells from all tissues. Polyamines are synthesized from two amino acids: L-methionine and L-ornithine (an amino acid that is not found in proteins, that is produced as part of the urea cycle).
In mammalian cells, putrescine is formed by decarboxylation of ornithine, a reaction catalyzed by the enzyme ornithine decarboxylase (ODC). Ornithine is available from the plasma and can also be formed within the cell from arginine by the action of arginase.
Synthesis of spermidine and spermine require the action of two enzymes: first, the S-adenosyl-methionine decarboxylase (AdoMetDC) for the synthesis of the aminopropyl donor; and second, a transferase enzyme (spermidine synthase or spermine synthase) which catalyze the transfer of the aminopropyl group to the primary amine groups of putrescine or spermidine, respectively.
Spermine and spermidine are also regulated by the presence of a distinctive interconversion pathway, where they are acetylated (by spermidine/spermine acetyltransferase SSAT), and oxidized (by polyamine oxidase POA) back to putrescine.
The third level of regulating polyamine metabolism is the terminal degradation of polyamines: oxidation of primary (terminal) amino groups produces polyamine derivatives that cannot be cycled back into polyamines. Polyamines are oxidized by variety of oxidases with different modes of action and co-factor requirements.
In light of their fundamental significance, it is unsurprising that the intracellular level of polyamines has to be maintained within very narrow limits. Decreases of polyamine levels interfere with cell growth, leading to G1 arrest in S. cerevisiae and to embryonic lethality in mice. Abnormally high levels of polyamines appear to be toxic, causing apoptosis in mammalian cells. Polyamine content is increased in many cancers arising from epithelial tissues, such as skin and colon.
The unique polyamine regulation
The first and rate-limiting enzyme in the polyamine biosynthesis pathway is ornithine decarboxylase (ODC). ODC is tightly regulated, and one of the most rapidly degraded mammalian proteins, and its degradation is regulated by polyamines in a ubiquitin independent manner.
This is achieved by a unique mechanism in which a polyamine-induced protein termed antizyme (Az) binds and inactivates ODC, and subsequently targets it to rapid ubiquitin-independent degradation by the 26S proteosome. Az was also demonstrated to regulate polyamine transport across the plasma membrane via a yet unknown mechanism. Az production requires a unique ribosomal +1 frameshift, which is stimulated by polyamines. Taken together, Az synthesis and Az function constitute a feedback regulatory circuit maintaining polyamine homeostasis.
Another protein relevant to the regulation of ODC and the cellular polyamine metabolism is a protein, termed antizyme inhibitor (AzI). AzI displays profound homology to ODC, but lacks ornithine decarboxylating activity. The affinity of Az to AzI was demonstrated to be higher than its affinity to ODC. Therefore, AzI can rescue ODC from its complex with Az, and prevent otherwise rapid degradation of ODC. Surprisingly, unlike the degradation of ODC, degradation of AzI is ubiquitin-dependant and inhibited by Az.
ODC activity is induced during growth stimulation of quiescent cells. and is constitutively increased in cells transformed by oncogenes, treated with carcinogens, infected by viruses, and in a variety of malignancies.
Polyamines and cell growth regulation
Normal cell growth is regulated in a cyclical manner by increase and/or decrease in specific proteins and protein kinases known as cyclins and cyclin-dependent kinases (cdks). ODC and polyamine concentrations also change during the cell cycle; There is an early peak of ODC at G1-phase, followed by an increase in polyamine content, and a latter, second increase during G2-phase and prior to mitosis. Therefore, both polyamines and cyclin/cdks show phased changes through the cell cycle, but the interaction between these two sets of regulatory molecules remains to be defined.
It is therefore not surprising that depletion of intracellular polyamine pool results in growth arrest. The arrest point varies with the type of polyamine-biosynthesis enzyme being inhibited and the drug used. For example, inhibition of ODC with its specific inhibitor DFMO results in a G1-phase block.
Polyamine depletion induces MAPK pathway and elevates the stress-regulated kinase (JNK) activity. Increased MAPK/JNK induces p53 tumor suppressor protein, which in turn may increase the transcription of p21, inhibiting cdk and causing accumulation of the hypophosphorylated form of the retinoblastoma protein.
As polyamines are tightly correlated with regulation of cellular growth, there has been an increasing effort over the past years to link polyamine metabolism to cancer. Increased polyamine levels are coupled with increased cell proliferation, decreased apoptosis and increased expression of genes associated with tumor invasion and metastasis, thus making their metabolism a target for cancer treatment and prevention.
However, numerous studies presenting evidence on the involvement of polyamines in modulation of cellular transcriptional responses are mostly sporadic, addressing specific notions and describing particular processes to be affected. Thus, generalized approach to the question of transcriptional regulation by polyamines is required to understand the mechanisms by which cells modify gene expression in adjustment to variation in polyamine levels.
This sounds to me to say that the N+ residues are forming alongisde - charges (out from the phosphate groups on the backbone?) on the DNA, creating a lattice or clathrate-like structure around it that changes the helix measurement. It's unclear if this has been proven in vivo or not to me, I read it to say that the measures were done with x-ray crystallography of prepared precipitates. I'm trying to make sense of the paper still -- from the results and discussion it seems they're using varying amounts of "monovalent" salts (Na+Cl-) along with polyamine to look at how this creates reinforced bonding in the DNA helix. In the complexity in vivo there are all sorts of other factors, including other salts.Interhelical Spacing in Liquid Crystalline Spermine and Spermidine-DNA Precipitates
Polyamines are ubiquitous small polycations with multiple functions in the cell growth and differentiation (Cohen, 1998; Tabor and Tabor, 1984).
Because of their positive charges, putrescine (2+), spermidine (3+), and spermine (4+) show a high affinity with the acidic constituents of the cell (RNA, DNA, ATP, acidic proteins, phospholipids, etc.).
Most of the intracellular polyamines are thought to be sequestered and “bound” to these cell constituents (Rubin, 1977; Davis et al., 1992; Watanabe et al., 1991).
The pool of “free” polyamines would show rapid fluctuations in response to intracellular signals (Veress et al., 2000).
Actually normal cells maintain the polyamine concentrations within narrow ranges by synthesis, catabolism, and transport that are regulated by hormones, growth factors, and feedback mechanisms. These intracellular concentrations that depend on the polyamine type, are estimated to be in the millimolar range (0.1–2 mM in mammalian cells, ∼7 mM in Neurospora crassa) (Davis et al., 1992; Watanabe et al., 1991).
Polyamine depletion as well as overproduction can lead to cell death (Thomas and Thomas, 2001). In cancer cells, however, the level of polyamines is significantly increased. As reported by Thomas et al. (2002), a cyclic process of increased polyamine synthesis and cancer cell growth appears to be sustained because high polyamine concentrations facilitate transcription of growth-related genes. To interfere with these cellular functions of natural polyamines, polyamine analogs have been designed and developed as therapeutic agents (for a review, see Thomas et al., 2002). All these studies display the essential role played by polyamines in the cell life, but little is known on the mechanism used by the polyamines to control the activity of the genome (Childs et al., 2003).
In solution, it has been shown that polyamines stabilize the double-stranded DNA helix (Tabor, 1962) and may induce changes in its conformation (B–Z transition) (Behe and Felsenfeld, 1981).
Polyamines also induce the collapse of isolated long DNA chains from dilute solutions with formation of toroids (Gosule and Schellman, 1976; Lambert et al., 2000; Bloomfield, 1996) showing a local hexagonal packing of DNA (Hud and Downing, 2001).
Multimolecular aggregates form using shorter DNA fragments of higher initial DNA concentration (Osland and Kleppe, 1977; Damaschun et al., 1978; Schellman and Parthasarathy, 1984).
Later on, it was shown, using short DNA fragment, 146-bp long, that the aggregate is liquid crystalline, either cholesteric or hexagonal when the precipitation is induced by spermidine (Sikorav et al., 1994; Pelta et al., 1996a,b) or by spermine (Pelta et al., 1996a), and the authors hypothesized that this state, combining ordering and fluidity of condensed DNA may be of biological interest.
X-ray diffraction analyses have been performed on these aggregates. In hexagonally packed DNA aggregates formed with spermine, a distance of 29.1 Å was found by Suwalsky et al. (1969). In aggregates formed with spermidine, Rau and Parsegian (1992) measured a distance of 29.75 Å, and Schellman and Parthasarathy (1984) obtained values comprised between 29.4 and 29.55 Å. Interestingly, two ranges of interhelix distances were found in spermidine-DNA aggregates: 31.6–32.6 Å in the cholesteric phase, 29.85 ± 0.05 Å in the hexagonal phase (Pelta et al., 1996a). Intermediate values were not obtained by changing the spermidine and sodium chloride concentrations. Instead, it was the relative amount of both phases that was modulated in the biphasic samples. We suspect that this variety of measured values comes either from metastability effects (Becker et al., 1979) or from differences in experimental conditions.
Materials and Methods
Before the structural measurements, the conductivity of the spermine chloride salt without DNA was determined for spermine concentrations ranging from 0.01 mM to 100 mM in distilled water, 200 mM NaCl, and 10 mM TE solution. To display the molar conductivity Λm of the spermine salt, the contribution of the residual salt, NaCl, and TE was simply subtracted from the conductivity data. Data, which are also divided by z = 4, are plotted in Fig. 2 as a function of κ (the inverse of the Debye screening length). This length takes into account the contribution of the different salts to the electrostatic screening. It may be written as:
equation M2 (1)
with z = 4, the spermine valence. In Fig. 2 the molar conductivity is found to decrease with κ. However two different variations are observed at low and high κ values. At low κ values or equivalently at low spermine salt concentration, a steep linear decrease is observed. By extrapolation to zero concentration, the limiting molar conductivity of the spermine salt is found equal to equation M3 in Siemens cm2 mol−1. Subtracting then the known contribution of the z chloride anions (Lide, 1999), we can extract the limiting ionic conductivity of spermine4+ 77.6 × z, a value close to the tabulated data 73.5 for the monovalent cation [NH4]+ (Lide, 1999). To understand this first variation, the properties of the ionic atmosphere around each ions must be taken into account. These properties are known to be responsible for the molar conductivity decrease that is commonly observed for completely dissociated electrolytes. This effect, called relaxation and electrophoretic effect, is described by the Debye-Hückel-Onsager theory. The theory predicts for the asymmetric spermine chloride salt the following limiting molar conductivity:
equation M4 (2)
where κ is expressed in Å−1 unit. The theoretical prediction, which is reported in Fig. 2, is in very good agreement with the experimental data in the left-handed side of the curve. Hence this first linear decrease is due to interionic attractive interactions and indicates that spermine is fully ionized at low concentration. In other words, the co-ions, i.e., the chloride anions, tend to surround the spermine cations or to create an “ionic atmosphere” around them.
In the right side of the curve, the molar conductivity still decreases when κ increases but with a low slope. In fact for strong electrolytes, deviation from the Debye-Hückel-Onsager prediction in its limiting form and even flattening of the molar conductivity are commonly reported at large salt concentrations. These deviations and flattening may be attributed to an effect of ion size that cannot be neglected for large κ values. In our case, a deviation without flattening is observed. This behavior—different from those reported for the classical fully dissociated electrolytes—suggests that some ion pairing could be formed in addition to the traditional “ionic atmosphere” and could be responsible for the continuous decrease of the molar conductivity.
[Ed.:I have difficulty interpreting the results, but think "efficient" may apply as a descriptor.]
The results, that we present here on natural polyamines, could be also important for the development of polyamine analogs as therapeutic agents. Polyamines are known to have preferential binding (Ruiz-Chica et al., 2001) or preferential spatial orientations in the DNA environment and they may also act as hydrators of DNA (van Dam et al., 2002). Their polycationic shape with discrete charges may also change the binding properties (Lyubartsev and Nordenskiöld, 1997). A modification of their chemical structures leads to a change of their binding properties. It changes the interhelical spacing between precipitated DNA (Schellman and Parthasarathy, 1984) as well as the precipitation conditions (Smirnov et al., 1988). In other words these analogs modify the DNA-DNA interaction and the cohesive energy of DNA. It could be informative to measure the spacing, to extract the corresponding cohesive energy when DNA chains are precipitated by different polyamine analogs and in parallel to determine their efficiency to inhibit the growth of cancer cells. Because polyamines are involved in many cellular processes, a simple correlation between the two effects may be not so evident. However we believe that differences in some of these processes should be observed and correlated to a change in the cohesive energy because DNA-DNA interactions are involved in many reactions. A beautiful example of modulations of these interactions has been reported by Srivenugopal et al. (1987) using a series of polyamine analogs, and connecting aggregation and enzymatic studies.
Endogenous polyamine function -- the RNA perspective
Recent progress with techniques for monitoring RNA structure in cells such as ‘DMS-Seq’ and ‘Structure-Seq’ suggests that a new era of RNA structure-function exploration is on the horizon. This will also include systematic investigation of the factors required for the structural integrity of RNA. In this context, much evidence accumulated over 50 years suggests that polyamines play important roles as modulators of RNA structure. Here, we summarize and discuss recent literature relating to the roles of these small endogenous molecules in RNA function. We have included studies directed at understanding the binding interactions of polyamines with polynucleotides, tRNA, rRNA, mRNA and ribozymes using chemical, biochemical and spectroscopic tools. In brief, polyamines bind RNA in a sequence-selective fashion and induce changes in RNA structure in context-dependent manners. In some cases the functional consequences of these interactions have been observed in cells. Most notably, polyamine-mediated effects on RNA are frequently distinct from those of divalent cations (i.e. Mg2+) confirming their roles as independent molecular entities which help drive RNA-mediated processes.
Polyamines play many roles in a wide variety of organisms (reviewed in (36,38–51)). For example, in mammals, polyamines function in diverse physiological processes including immunity, aging, hair growth and wound healing. Accordingly, the cellular concentrations of polyamines reflect these functions and vary widely according to cell type and context. In terms of cellular mechanisms, polyamines play important roles in messenger RNA (mRNA) translation and stability, both in a global sense as well as in specific cases. In addition, they are reported to modulate kinase activities, small RNA methylation, transcriptional regulation, microtubule assembly and ion channel regulation. Through a unique mechanism, spermidine also acts as precursor of hypusine (Figure 1), a post-translationally modified amino acid of the initiation factor elF5a in protein synthesis (52). Numerous works have described how polyamines regulate their own homeostasis, using some of the aforementioned mechanisms (reviewed in (42,53–56)). In spite of the multitude and diversity of processes which polyamines are known to influence, mechanistic insight into how they perform these functions is usually sparse.
Polyamines function through direct and indirect influences on the structure and stability of a variety of macromolecules. For example, polyamines are known to directly bind and in some cases stabilize and/or induce transitions between B-form, Z-form, A-form, triplex and quadruplex-form DNA. In these cases, polyamine-DNA binding selectivity for G–C-rich major grooves, A–T homo-dimers, as well as A, A–T and Pu-Py tracts has been reported (57–66). Indirectly, polyamines can function as scavengers of oxygen free radicals, and consequently protect nucleic acid and other cellular components from oxidative damage (67). Of note, oxidation-driven polyamine catabolism acts as a source of hydrogen peroxide, a precursor for reactive oxygen species, as well as reactive aldehydes both of which are capable of damaging cellular components (55,67). This suggests that the cellular damage resulting from the depletion of polyamines is escalated by the evolving toxic products of the oxidase responsible for their depletion (67).
mRNA and snRNA
The ‘polyamine modulon’ is a set of genes whose expression is enhanced by polyamines at the level of translation (36,83,84). Polyamine modulons have been identified in yeast, mammalian cells and E. coli (83,85–88). In the majority of cases, the mechanisms underlying polyamine-mediated stimulation of translation are unknown, however, several hypotheses have been forwarded (36,83). These include: enhancement of translation initiation at inefﬁcient codons, e.g. for Cya, Cra, SpoT, UvrY, RRF in E. coli; changes in the position of an obscure or distant Shine-Dalgarno (SD) sequence, e.g. for FecI, Fis, RpoN, H-NS RpoZ, OppA, RMF and CpxR; stimulation of read through of an amber codon (RpoS) and stimulation of a plus-one (+1) frame-shift (PrfB) (83,87,89–92).
In mammalian cells and yeast, attention has predominantly focused on the influence of polyamines on ribosomal shuttling, e.g. for Cox4 and Cct2 (85,86). It is conceivable that in some of these cases direct interactions between the polyamine and the mRNAs are responsible. This implies that polyamines are ligands for riboswitches in the genes of the polyamine modulon. Several riboswitch elements have been characterized in bacteria for which a wide variety of ligand structures are known (e.g. lysine, Mg2+, F− and S-adenosylmethionine) (93). However, polyamines have not been demonstrated to perform such a role, despite strong circumstantial evidence outlined below.
Other techniques have been used to investigate polyamine–tRNA interactions, including Fourier transform infrared spectroscopy (FTIR), analysis of UV differential melting curves, electron spin resonance (ESR) spectroscopy, RNase foot-printing, equilibrium dialysis, molecular modeling, cleavage assays, competition assays and CD (81,96,124–135). Selected examples are discussed below.
Taking the lessons from these studies together, it is clear that specific polyamine dependencies are likely decisive for the proper folding of particular tRNA species at various stages of protein synthesis, and that chelated polyamines and divalent ions play distinct structural roles. The observations put to rest the simplistic notion that polyamines are simply organic cations, analogous to Mg2+ and K+.
SUMMARY AND OUTLOOK
In spite of their critical roles in many cellular processes, the mechanistic workings of polyamines are rarely investigated. Indeed, one can argue that polyamines still reside in ‘the box-room of biochemistry’ (166). One reason is the inherent difficulties in designing and interpreting experiments involving these small ubiquitous molecules, as evidenced by many incongruences in the literature associated with the nature of polyamine–RNA interactions. The main reason, however, is likely their lack of molecular complexity which, paradoxically, implies functional simplicity: polyamines are still mostly seen as poly-cations, despite the well-known non-interchangeability of even the simplest cationic species, Mg2+ and Ca2+ in biological systems (166).
As for metal ions (167), two distinct modes of binding to RNA can be expected for polyamines (105,111): an orthodox non-specific manner, where polyamines diffuse within a restricted volume around the nucleic acid or its hydrated environment and a site-specific mode, where it is chelated in a defined binding pocket via direct interactions with distinct nucleic acid residues. In the latter case, these interactions will be governed by the polyamine structure, its protonation state, the RNA structure and sequence and the ionic environment. Furthermore, polyamines can be covalently modified, for example by oxidation, acetylation or conjugation (references cited in (55,67,168)), potentially increasing the ways in which they might interact with RNA. Our survey of the literature has highlighted many examples of polyamines interacting with RNA in a sequence/structure-selective manner (often with functional consequences).
Where investigated, a majority of the polyamine binding sites were distinct from those that bind Mg2+. In addition, preferential binding sites for polyamines are important for specific functions of rRNA, tRNA and antibiotics; furthermore cross-linking also affected these functions. Several in vitro and in vivo investigations revealed the bulged nucleotides of stems in mRNA and snRNA, and a mismatch in a tRNA stem, as required features for stem stabilization by spermidine. Spermidine-specific effects included stimulating initiation of mRNA translation, modifying the viral protein binding capacity of a snRNA and charging the tRNA. Where investigated, Mg2+ could not substitute for the polyamine, providing strong evidence that polyamines do indeed interact with RNA in specific fashions and that the interactions direct and/or modulate RNA functions.
Taken together, the evidence that polyamines directly regulate key RNA functions is wide-ranging and substantial. Thus, natural adjustments in the cellular concentrations of specific polyamines have the potential to control this regulation by shifting the dynamics of RNA structure. To date, the primary focus of investigations has been the protein synthesis pathway. However, polyamines have also been shown to interact with viral RNAs (169,170). Additionally, polyamines modulate a variety of additional processes, such as splicing and helicase activity, all of which could involve direct interactions with RNAs. Hence, mechanistic investigations into polyamine–RNA regulation on the transcriptome scale in vivo (171–174) or even in vitro (as recently performed for Mg2+ (173)) would be highly informative. We are looking forward to a new era of exploration in the polyamine–RNA field.
The authors thank Mirjam Menzi for performing preliminarily literature searches for two of the topics covered in this review.