NUCLEAR MATRIX-ASSOCIATED POLY(ADPRIBOSYL)ATION SYSTEM IN RAT TESTIS CHROMATIN

The presence of poly(ADPR)polymerase in the third level of rat testis chromatin, i.e., in stripped chromatin loops and nuclear matrix, was a ssessed using enzymatic assays, activity blots, and Western blots. The distribution and the size of ADPribose polymers associated to protein s of the same nuclear fractions was analyzed after incubation of intac t isolated nuclei with [C-14]- Or [P-32]NAD(+). Short ADPribose oligom ers, not larger than 3 residues, were found to be associated to tightl y bound chromosomal proteins, which resisted extraction by 2 M NaCl, w hereas longer oligomers (8-13 residues long) were associated to loosel y bound chromosomal proteins. The identity of ADPribose-protein conjug ates was determined by autoradiographic analysis of nuclear protein ex tracts. Tightly bound histone-like proteins appear to be ADPribosylate d both in stripped chromatin loops and in nuclear matrix. (C) 1994 Aca demic Press, Inc.