Contributions of transcriptional and post-transcriptional mechanisms to the regulation of c-myc expression in mouse erythroleukemia cells.
Chemically induced differentiation of mouse erythroleukemia (MEL) cells leads to complex changes in c-myc mRNA levels. Within 1-2 hr after the addition of the inducer hexamethylene bisacetamide (HMBA), c-myc mRNA levels decrease 10- to 20-fold and remain low until 12-24 hr, at which time the mRNA reaccumulates to its original level. Thereafter as the cells undergo terminal differentiation, c-myc mRNA again declines to a low level. We have investigated the regulation of these changes by measuring c-myc gene transcription and mRNA turnover. We find that the early rapid decline in c-myc mRNA is due to an increase in the block to elongation of transcription within the c-myc first exon. Effective c-myc transcription is then restored after 2 hr of HMBA treatment to the level present in uninduced cells and is maintained throughout the remainder of the differentiation program. These results demonstrate that, except for the rapid decline in c-myc mRNA immediately following inducer treatment, all subsequent regulation of message levels occurs through post-transcriptional mechanisms. Studies of c-myc mRNA turnover suggest that some post-transcriptional regulation is nuclear.
D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics; D007942:Leukemia, Experimental / Q000235:genetics*; D051379:Mice; D011519:Proto-Oncogenes; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D000081:Acetamides; D012333:RNA, Messenger; D003609:Dactinomycin; C014026:hexamethylene bisacetamide