title: Hexamethylenebisacetamide-resistant murine erythroleukemia cells have altered patterns of inducer-mediated chromatin changes.
abstract: We determined inducer-mediated changes in chromatin structure near the globin genes in a variant line of murine erythroleukemia cells (MELC). The variant cell line, R1, was derived from the inducer-sensitive DS19 cell line by selection for inducer-resistance. R1 cells are resistant to induction of erythroid differentiation by hexamethylenebisacetamide (HMBA) whereas the parental line is HMBA-sensitive. Uninduced MELC (both inducer-sensitive DS19 cells and inducer-resistant R1 cells) have DNase I-sensitive sites in chromatin containing the alpha 1- and beta maj-globin genes. These nuclease-sensitive regions are located within the beta maj-globin second intervening sequence (IVS2) and near the alpha 1-globin gene 5' cap site. Culture with HMBA causes changes in chromatin structure in both parental and variant cell lines. In DS19 cells, the DNase I-sensitive site within the beta maj-globin IVS2 becomes more resistant to nuclease cleavage, and a new DNase I-sensitive region develops near the beta maj-globin cap site. In addition, the nuclease-sensitive region adjacent to the cap site of the alpha 1-globin gene increases, and a novel 5' nuclease-sensitive site is also established. In R1 cells, HMBA-mediated changes in chromatin structure are incomplete. The DNase I-sensitive site within the beta maj-globin IVS2 becomes more resistant to nuclease cleavage, but the nuclease sensitivity near the beta maj-globin cap site does not increase to the extent observed in DS19 cells. The pattern of nuclease sensitivity near the alpha 1-globin gene is essentially unchanged after culture of R1 cells with HMBA. Thus, in R1 cells, resistance to HMBA-induced expression of globin genes is associated with failure to detect inducer-mediated changes in chromatin structure 5' to the cap site of the alpha 1- and beta maj-globin genes. These results also suggest that the increased nuclease resistance of a site in the beta maj-globin IVS2 does not depend on the establishment of a DNase I-sensitive region near the beta maj-globin gene cap site.
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000187:drug effects / Q000502:physiology*; D003850:Deoxyribonuclease I; D004351:Drug Resistance; D004706:Endodeoxyribonucleases; D014644:Genetic Variation; D007942:Leukemia, Experimental / Q000235:genetics / Q000503:physiopathology*; D051379:Mice
chemical_list: D000081:Acetamides; D002843:Chromatin; D004706:Endodeoxyribonucleases; D003850:Deoxyribonuclease I; C014026:hexamethylene bisacetamide