title: DNAase I sensitivities in chromatin of the Xenopus laevis somatic and oocyte 5 S DNAs.
abstract: The DNAase I sensitivities of the somatic-type 5 S DNA and oocyte-type 5 S DNA have been compared in nuclei from adult somatic tissues of Xenopus laevis. Neither of these Type III genes is expressed in mature erythrocytes and only somatic-type 5 S DNA is expressed in liver. We find that somatic-type 5 S DNA is DNAase-I-sensitive in liver nuclei and less sensitive in erythrocyte nuclei, while oocyte-type 5 S DNA is insensitive in both tissues. The DNAase I sensitivity appears to be uniform across each active somatic-type 5 S DNA repeat. Two regions slightly hypersensitive to DNAase I are found only in liver somatic-type 5 S DNA. One of these regions is within the gene, overlapping with the binding site of the transcription factor (TF III A) required for 5 S RNA synthesis. Thus, the correlation between DNAase I sensitivity and gene activity previously seen for protein-coding genes also holds for these Type III genes. Our data lead us to suggest that the fully DNAase-I-sensitive chromatin conformation on 5 S DNA requires the presence both of transcription factors and RNA polymerase.
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002843:Chromatin / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism*; D004912:Erythrocytes / Q000032:analysis; D005260:Female; D008099:Liver / Q000032:analysis; D009690:Nucleic Acid Conformation; D009865:Oocytes / Q000032:analysis*; D013379:Substrate Specificity; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014982:Xenopus laevis
chemical_list: D002843:Chromatin; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D004247:DNA; D003850:Deoxyribonuclease I