Abstract
Polyamines are involved in various biological functions, including cell proliferation, differentiation, gene regulation, etc. Recently, it was found that polyamines exhibit biphasic effects on gene expression: promotion and inhibition at low and high concentrations, respectively. Here, we compared the effects of three naturally occurring tetravalent polyamines, spermine (SPM), thermospermine (TSPM), and N4-aminopropylspermidine (BSPD). Based on the single DNA observation with fluorescence microscopy together with measurements by atomic force microscopy revealed that these polyamines induce shrinkage and then compaction of DNA molecules, at low and high concentrations, respectively. We also performed the observation to evaluate the effects of these polyamine isomers on the activity of gene expression by adapting a cell-free luciferase assay. Interestingly, the potency of their effects on the DNA conformation and also on the inhibition of gene expression activity indicates the highest for TSPM among spermine isomers. A numerical evaluation of the strength of the interaction of these polyamines with negatively charged double-strand DNA revealed that this ordering of the potency corresponds to the order of the strength of the attractive interaction between phosphate groups of DNA and positively charged amino groups of the polyamines.
Highlights
IntroductionIt is well known that polyamines play important roles in many biological functions, such as cell proliferation, differentiation, apoptosis, and gene regulation [1–7]
Polyamines are small multivalent cations that exist in all living organisms
It was reported that the change in the conformation of DNA induced by polyamines causes a change in genetic activity through a cell-free gene expression assay [3,27–30]
Summary
It is well known that polyamines play important roles in many biological functions, such as cell proliferation, differentiation, apoptosis, and gene regulation [1–7] They interact with negatively charged macromolecules such as DNA, RNA, and proteins, and thereby regulate the structure and function of these macromolecules [3,8–16]. It was found that polyamines exhibit biphasic effects on gene expression: promotion and inhibition at low and high concentrations, respectively [31]. This promotion is attributable to the specific shrunken conformation of DNA, which is characterized by parallel ordering among the neighboring DNA segments. Inhibition of gene expression is due to the formation of a tightly packed com arrangement in the higher-order structure of DNA at higher concentrat2ioofn1s3 of poly ines. The DNA concentration was set at 0.3 μM in nucleotide units
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