Comparative subunit structure of HeLa, yeast, and chicken erythrocyte chromatin.

We have compared the chromatin subunit structure of yeast, HeLa, and chicken erythrocyte by analyzing the DNA fragments produced by in situ digestion with staphylococcal nuclease (EC 3.1.4.7) and DNase I(EC 3.1.4.5). The repeat size of the chromatin varies among (and within two of) the three organisms but the size and the structure of the most nuclease-resistant "core" of the repeat is the same. Thus, the interspecies differences in repeat size are due to different lengths of nuclease-sensitive "spacer" DNA between the cores. There also seems to be a difference in the manner of spacing of cores; the transcriptionally active (yeast and HeLa) chromatins have spacings of variable length while the transcriptionally inactive (chicken erythrocyte) has a more regular spacing of cores.