A transcriptional arrest mechanism involved in controlling constitutive levels of mouse c-myb mRNA.
The control of c-myb mRNA abundance was examined in three representative cell lines, (the erythroleukaemia F4-12B2, the myeloma MOPC-31C and the fibroblast NIH3T3), which display abundant, low and undetectable levels of this transcript, respectively. We observed a small difference in half-life between F4-12B2 and MOPC-31C c-myb mRNA (175 min and 105 min, respectively) insufficient to account for the approximately 20-fold lower levels of this transcript in myelomas. Using the run-on transcription assay we found that c-myb transcripts were initiated at similar rates in all three cell types and were elongated at this relatively high rate to a site approximately 2 kilobases into the first intron. NIH3T3 c-myb transcripts did not proceed detectably beyond this pause/attenuation site, while in F4-12B2 cells transcription of regions 3' of this site occurred at a rate approximately 12-fold greater than in MOPC-31C. We have concluded that this transcriptional arrest mechanism, together with small differences in RNA turnover, were sufficient to account for the spectrum of c-myb mRNA abundance observed. Despite evidence of transcript initiation, we were unable to detect c-myb mRNA in fibroblasts, even under conditions (e.g. serum stimulation) which induced high c-myc mRNA levels. However, a novel 3.0 kilobase transcript with homology to c-myb was detected in cycloheximide-treated NIH3T3 cells.
Watson
R J
RJ
Imperial Cancer Research Fund Laboratories, St Bartholomew's Hospital, London, UK.
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D005347:Fibroblasts / Q000502:physiology; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics*; D051379:Mice; D010954:Plasmacytoma / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger