DOES POLY(ADP-RIBOSYL)ATION REGULATE THE DNA METHYLATION PATTERN

The existence of a possible correlation between poly(ADP-ribosyl)ation and DNA methylation processes was investigated. In vivo and in vitro experiments were carried out on L929 mouse fibroblasts preincubated fo r 24 h with or without 3-aminobenzamide, a well-known inhibitor of pol y(ADP-ribose) polymerase. Both experimental approaches evidenced a clo se relationship between these two important nuclear enzymatic mechanis ms, suggesting that the poly(ADP-ribosyl)ated isoform of H1 histone an d/or long and branched protein-free ADP-ribose polymers could act as p rotecting agents against full methylation of the CpG dinucleotides in genomic DNA.