title: The first exon of the c-myc proto-oncogene contains a novel positive control element.
abstract: We have identified a positive modulator within the c-myc first exon downstream of the gene's transcription initiation sites, P1 and P2. We introduced myc-CAT (chloramphenicol acetyltransferase) hybrid genes into three cell lines (BJAB, COS and HeLa) and measured their expression by either CAT enzymatic activity, S1 nuclease protection or by a nuclear 'run-on' transcription assay. Removal of 46 bp from the 3' end of the first exon results in a decrease of myc-CAT expression and P2 activity. A 438-bp exon 1 segment, lacking the normal myc promoters, efficiently drives the expression of SV40 early promoters. We find that this first exon segment efficiently functions as a positive modulator only in its sense orientation, 3' of a nearby promoter. The positive effects of the myc first exon and the SV40 enhancer are complementary.
mesh_terms: D000818:Animals; D002460:Cell Line; D004262:DNA Restriction Enzymes; D004720:Endonucleases; D004742:Enhancer Elements, Genetic; D005091:Exons; D005814:Genes, Viral; D005822:Genetic Vectors; D011519:Proto-Oncogenes; D013539:Simian virus 40 / Q000235:genetics; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014158:Transcription, Genetic
chemical_list: D004720:Endonucleases; D004262:DNA Restriction Enzymes; D015719:Single-Strand Specific DNA and RNA Endonucleases