The c-myc gene encodes superimposed RNA polymerase II and III promoters.
The first exon of the c-myc gene has unusual properties that suggest some further role in gene regulation. It encodes a large, evolutionarily conserved leader exon that is transcribed more frequently than the remaining exons of the c-myc gene. In what follows, we provide a possible explanation for these observations. We find that the major promoter of the c-myc gene is bifunctional; that is, it supports transcription by RNA polymerases II and III (pol II and III). Both enzymes initiate in vitro transcription from the major c-myc initiation site (P2), but pol III is completely blocked near the 3' end of the first exon while pol II, though partially blocked, transcribes through this region. These superimposed transcriptional activities suggest a potential regulatory mechanism by which one polymerase system could influence the activity of another.
Department of Genetics, Harvard Medical School, Howard Hughes Medical Institute, Boston, Massachusetts 02115.
J
J
Chung
D J
DJ
Sussman
R
R
Zeller
P
P
Leder
D000818:Animals; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005091:Exons; D006801:Humans; D011401:Promoter Regions, Genetic; D011519:Proto-Oncogenes; D012319:RNA Polymerase II / Q000235:genetics*; D012320:RNA Polymerase III / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014982:Xenopus laevis
D012319:RNA Polymerase II; D012321:DNA-Directed RNA Polymerases; D012320:RNA Polymerase III