Interactions of poly(N.epsilon.,N.epsilon.,N.epsilon.-trimethyllysine) and poly(lysine) with polynucleotides: circular dichroism and A-T sequence selectivity

Publisher Website
Google Scholar
Abstract
Complexes of (Lys)n and [Lys(Me3)]n with natural and synthetic DNA were studied by CD (circular dichroism) as a function of ionic strength. In dilute EDTA, (Lys)n and [Lys(Me3)]n produce the same distortions to the CD spectrum of calf thymus DNA at r (peptide residue/nucleotide residue) values < 0.6. At higher r values, the distortions are somewhat different. [Lys(Me3)]n alters the conformation of some polynucleotides differently from (Lys)n under non-.psi. conditions. Therefore, methylation of histones may serve to alter the structure of chromatin. At low ionic strength, [Lys(Me3)]n and (Lys)n alter the viscosity of DNA to the same extent between r values of 0.0 and 1.0. In contrast to (Lys)n-DNA, at high ionic strengths, [Lys(Me3)]n-DNA does not show .psi.-type CD spectra. (Lys)n forms .psi.- structures with (dA-dT)n and (dG-dC)n. [Lys(Me3)]n forms .psi.- structures with (dA-dT)n. Between 0.05-0.3 M NaCl, [Lys(Me3)]/n forms .psi.+ structures with (dG-dC)n, while between 0.35-0.45 M NaCl, it forms a .psi.- structure with (dG-dC)n. Neither (Lys)n nor [Lys(Me3)]n forms .psi. structures with (dA)n.cntdot.(dT)n or (dG)n.cntdot.(dC)n. These results, in conjunction with the work of others on reconstitution of nucleosome-like particles from synthetic polynucleotides, suggest that the ability of DNA and histones to form nucleosomes is related to the formation of .psi. structures. (Lys)n binds preferentially to (dA)n .cntdot. (dT)n over (dA-dT)n. [Lys(Me3)]n binds to (dA)n.cntdot.(dT)n and (dA-dT)n with equal affinity.