DNA sequences that mediate attenuation of transcription from the mouse protooncogene myc.

Expression of the protooncogene myc is regulated by multiple mechanisms and is probably involved in the control of cellular proliferation. Modulation of transcriptional elongation by attenuation within exon 1 of the myc gene is thought to play an important role in determining levels of myc RNA in both normal and tumor cells. We show that the first exon of mouse myc contains specific DNA sequences that may mediate transcriptional attenuation. A 180-nucleotide DNA fragment derived from the 3' end of exon 1 reduced transcriptional elongation by polymerase II when placed within an intron of the human alpha 1-globin gene and assayed by transfection into HeLa cells. A 36-nucleotide sequence that resembles a variety of transcriptional termination signals was located within this myc fragment but was by itself insufficient to cause attenuation when placed within the alpha-globin gene. Modulation of transcriptional elongation through specific DNA sequences within a gene may thus provide a mechanism for regulating its expression.