Myc versus USF: Discrimination at the cad gene is determined by core promoter elements

Kathryn E. Boyd, Peggy J. Farnham

Research output: Contribution to journalArticlepeer-review

135 Scopus citations


Carbamoyl-phosphate synthase/aspartatecarbamoyltransferase/dihydroorotase, which is encoded by the cad gene, is required for the first three rote-limiting steps of de novo pyrimidine biosynthesis. It has been previously demonstrated that cad transcription increases at the G1/S phase boundary, as quiescent cells reenter the proliferative cell cycle. The growth-responsive element has been mapped to an E box at +65 in the hamster cad promoter. Using an in vivo UV cross-linking and immunoprecipitation assay, we show that Myc, Max, and upstream stimulatory factor (USF) bind to the chromosomal cad promoter. To determine whether binding of Myc-Max or USF is critical for cad growth regulation, we analyzed promoter constructs which contain mutations in the nucleotides flanking the E box. We demonstrate that altering nucleotides which flank the cad E box to sequences which decrease Myc-Max binding in vitro correlates with a loss of cad G1/S-phase transcriptional activation. This result supports the conclusion that binding of Myc-Max, but not USF, is essential for cad regulation. Our investigations demonstrate that the endogenous cad E box can be bound by more than one transcription factor, but growth-induced cad expression is achieved only by Myc.

Original languageEnglish (US)
Pages (from-to)2529-2537
Number of pages9
JournalMolecular and Cellular Biology
Issue number5
StatePublished - May 1997
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology


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