Changes in promoter utilization in human and mouse c-myc genes upon transformation induction in temperature-sensitive cell lines.
We have previously reported accelerated transcription and rapid accumulation of c-myc mRNAs upon induction of transformation in a temperature-sensitive mouse cell line (Gallant et al., 1989, Oncogene Res., 4:39-46). Here we have used both mouse and human cell lines transformed with a temperature-sensitive mutant of the Simian virus 40 (SV40) virus to investigate whether a shift in promoter utilization within the c-myc gene locus is part of a general mechanism that deregulates c-myc expression during transformation induction. We devised a simple and sensitive method using reverse transcription followed by radioactive polymerase chain reaction (RT-PCR) to measure the relative change in c-myc mRNAs arising from each of the four known promoters. We show that a three to fivefold increase in c-myc transcripts from the P1 and P3 promoters occurs in both human and mouse cell lines within 30 min of the shift to the permissive temperature. The major P2-initiated transcripts are not significantly effected. However, exon 3-containing RNAs increase more gradually up to 24 h postinduction and P1 and P3 transcripts, while remaining elevated, still contribute relatively little to the total c-myc RNA population. These and other results, demonstrating a transient activation of P1 and P3 promoters, suggest an indirect role of the minor transcripts in the deregulated expression of the c-myc gene in transformed cells.
Luo
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Department of Biology, University of New Brunswick, Fredericton, Canada.
Krause
M O
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D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002472:Cell Transformation, Viral; D004247:DNA; D005786:Gene Expression Regulation; D016259:Genes, myc; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012260:Ribonucleases / Q000378:metabolism; D013696:Temperature
D016271:Proto-Oncogene Proteins c-myc; D004247:DNA; D012260:Ribonucleases