Studies on the degradation of ageing chromatin DNA by nuclear and cytoplasmic factors and deoxyribonucleases.

Abstract

There are 'factors' in both the cytoplasm and the nucleus which are capable of a limited digestion of the DNA in chromatin. These factors show a pH optimum closer to that of DNase I than DNase II and do not promote the activities of either of these purified enzymes. These factors show considerable tissue specificity, for example, liver extracts are less able to degrade kidney chromatin than the homologous chromatin (40% difference) and slight age specificity since 'age-matched' samples gave consistently higher (10%) extents of degradation. There is no evidence, however, with increasing age in mice, that the accessibility of DNA in chromatin to digestion by deoxyribonucleases is altered.