Reassembly of c-myc and relaxation of c-fos nucleosomes during differentiation of human leukemic (HL-60) cells.
Human promyelocytic leukemic (HL-60) cells have amplified c-myc protooncogene sequences which lead to an elevated level of c-myc gene expression. Induction of HL-60 cells by phorbol esters to undergo monocytic differentiation results in the suppression of c-myc, but the activation of c-fos gene transcription. Chromatin structures of c-myc and c-fos were compared by measuring their sequences in nucleosome-associated DNA fragments. These nucleosomal particles were released from chromatin by micrococcal nuclease digestion and subsequently analyzed with two dimensional gel electrophoresis. C-myc related sequences were detected in nucleosomal DNA fragments of differentiated cells only, while the c-fos related sequences were found in nucleosomal DNAs of noninduced HL-60 cells. Since the enzyme preferentially digests relaxed DNAs, these results suggest that nucleosomal subunits of c-myc and c-fos chromatin are relaxed during the state of active transcription, and reassembled once their transcription is repressed.
D002454:Cell Differentiation / Q000187:drug effects; D005786:Gene Expression Regulation; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000473:pathology; D009707:Nucleosomes / Q000648:ultrastructure*; D011479:Protamines / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D011519:Proto-Oncogenes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic
D009707:Nucleosomes; D011479:Protamines; D011518:Proto-Oncogene Proteins; D013755:Tetradecanoylphorbol Acetate