title: The nuclease sensitivity of active genes.
abstract: Brief micrococcal nuclease digestion of chick embryonic red blood cells results in preferential excision and solubilization of monomer nucleosomes associated with beta-globin sequences and also 5'-sequences flanking the beta-globin gene. Both regions are DNAse-I sensitive in nuclei. Such salt-soluble nucleosomes are enriched in all four major HMG proteins but HMG1 and 2 are only weakly associated. These nucleosomes appear to have lost much of the DNAse-I sensitivity of active genes. The HMG14 and 17-containing salt-soluble nucleosomes separated by electrophoresis are not DNAse-I sensitive and contain inactive gene sequences as well as active sequences. Reconstitution of HMG proteins onto bulk nucleosomes or chromatin failed to reveal an HMG-dependent sensitivity of active genes as assayed by dot-blot hybridization and it was found that the DNAse-I sensitivity of ASV proviral sequences as assayed by dot-blot hybridization was not HMG-dependent. These results indicate that higher order chromatin structures might be responsible for nuclease sensitivity of active genes.
mesh_terms: D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D001483:Base Sequence; D002471:Cell Transformation, Neoplastic; D002645:Chickens; D004247:DNA / Q000097:blood*; D003850:Deoxyribonuclease I; D004706:Endodeoxyribonucleases; D004912:Erythrocytes / Q000378:metabolism*; D005796:Genes; D005914:Globins / Q000235:genetics; D008836:Micrococcal Nuclease / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D009707:Nucleosomes / Q000378:metabolism; D010047:Ovalbumin / Q000235:genetics; D051381:Rats
chemical_list: D009707:Nucleosomes; D005914:Globins; D010047:Ovalbumin; D004247:DNA; D004706:Endodeoxyribonucleases; D003850:Deoxyribonuclease I; D008836:Micrococcal Nuclease