Chromatin proteins surrounding the d(G-T)n repeats and polyamine influence as revealed by photoaffinity labeling with reactive pd(A-C)6 derivatives

The complementary-addressed modification of DNA and proteins in chromatin using photoreactive derivatives of pd(AC)6 has been studied. These oligonucleotides form complementary complexes with specific DNA sequences and modify both DNA and proteins in the vicinity of these regions, and can be used for investigation of the protein environment in DNA. We have demonstrated that photoreactive derivatives of oligonucleotides can quickly and efficiently modify chromatin proteins and seem to be promising for investigation of perturbations in chromatin structure during the cell cycle. A comparison between modified chromatin from synchronized cells has demonstrated differences in the sets of proteins modified in the S and G1/S phases of the cell cycle. An increase in spermine and spermidine concentrations leads to an increase in modification of definite chromatin proteins. It can be supposed that the B-Z transition that can be stabilized by the presence of natural polyamines is one of the reasons for the presence of single-stranded DNA regions, containing sets of (dG-dT)n and accessible for interaction with complementary oligonucleotides.