TRANSCRIPTIONALLY ACTIVE XENOPUS-LAEVIS SOMATIC 5 S RIBOSOMAL-RNA GENES ARE PACKAGED WITH HYPERACETYLATED HISTONE H4, WHEREAS TRANSCRIPTIONALLY SILENT OOCYTE GENES ARE NET

The relationship between histone acetylation and transcription of the Xenopus laevis oocyte and somatic 5 S ribosomal RNA genes was investig ated, Chromatin fragments from a X. laevis kidney cell line were immun oprecipitated with an antibody specific for hyperacetylated histone H4 . The DNA from the hyperacetylated chromatin was probed with both oocy te- and somatic gene-specific sequences, and the results showed that t he upstream, nontranscribed region of the transcriptionally active som atic genes is packaged with acetylated histone H4. In contrast, the co rresponding region of the transcriptionally silent oocyte genes is pac kaged with hypoacetylated histone H4 in this cells line. Further study also showed that this region of the oocyte genes was less sensitive t o digestion with the enzyme, micrococcal nuclease, Together these resu lts suggest that, as described for both RNA polymerase I and II transc ribed genes, there is a correlation between histone acetylation and tr anscription of the RNA polymerase III transcribed 5 S ribosomal RNA ge nes in X. laevis.