Strom R, Caiafa P, Mastrantonio S, Rispoli M, Reale A, Attinà M, Cacace F. A possible role of chromatin and tightly-bound chromatin proteins on enzyme-catalyzed methylation of DNA.
CELL BIOPHYSICS 1989;
15:149-57. [PMID:
2476222 DOI:
10.1007/bf02991587]
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Abstract
Upon extensive digestion with DNAaseI of placenta chromatin matrix, previously "stripped" from its loosely-bound components by high-salt extraction, a fraction is obtained that contains almost no endogenous DNA methylase activity but whose DNA, if still included in this whole fraction--not if it has been purified to a protein-free condition--is a good substrate for externally added enzyme. This chromatin matrix can even cause a significant stimulation of methylation of single-stranded Micrococcus luteus DNA by placental methylase. In vivo, this phenomenon may have possible counterparts in the existence of highly-methylated regions of chromatin loops that appear to be protected by tightly-bound protein components from digestion of the "stripped loops" with DNAaseI.
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