Activation of c‐myc promoter by c‐myc protein in serum starved cells

Abstract

The function of the c-myc protein, the product of a proto oncogene, is not clearly understood although many reports, including ours, suggest that the c-myc protein plays several roles in the regulation of transcription and DNA replication. Here we examined the effects of c-myc protein on transcription from the c-myc promoter, and by inference its role in auto-regulation, after introducing into cultured cells a c-myc expression vector and a CAT reporter gene linked to the promoter and upstream region of the human c-myc gene. To minimize the effects of the endogenous c-myc protein on the exogenously added CAT reporter gene, the transfected cells were treated under serum-free conditions. The results show that CAT expression from the myc promoter increased in a dose-dependent manner Efter addition of the c-myc expression vector, and that it also required the presence of a c-myc binding sequence previously identified 2 kb upstream from c-myc's first exon.Moreover, the domains of the c-myc protein important for transactivation were determined by use of various deletions mutants of c-myc cDNA. The results showed that the N-terminal portion in the c-myc protein was necessary for transactivation beside the C-terminal portion containing basic region, helix-loop-helix, and leucine zipper.

MSSP promotes ras/myc cooperative cell transforming activity by binding to c‐Myc

“…A deletion construct of the c-myc gene, pGEM-c-mycD(ClaI-StyI), was described previously (Kitaura et al 1991). The BamHI-EcoRI fragment of pGEM-c-mycD(ClaI-StyI) was inserted to the BamHI-EcoRI sites of pGEX2TK, and the resultant plasmid was named pGEX-c-mycD(ClaI-StyI).…”

AMY‐1, a novel C‐MYC binding protein that stimulates transcription activity of C‐MYC

“…For pGADGH-AMY(HX), PCR was carried out with AMY(H-X)ATG and T7 primers on pBS-AMY-1 as a template and the product was similarly cloned in pGADGH as above. Deletion constructs of c-myc were as described previously (Kitaura et al 1991). PCRs were carried out with T7 and c-myc(GKPG)ATG primers on the c-myc deletion mutants in pGEM4Z.…”

The Myc Negative Autoregulation Mechanism Requires Myc-Max Association and Involves the c-myc P2 Minimal Promoter

“…Others have postulated that Myc autosuppression may operate through c-Myc inhibition of the activity of YY-1, a transcription factor involved in upregulation of c-myc P1 and P2 transcription (87,94). Alternative results implicate a role for the c-myc promoter and specifically for the TCTCTTA positive control element 1.4 kb upstream of the P1 promoter (54) or for the nearby CTF/NF-1 sites (62,111). These conflicting results may reflect differences in the assays and cell types used in the various studies.…”