Members of the USF family of helix-loop-helix proteins bind DNA as homo- as well as heterodimers

Gene Expr. 1992;2(3):231-40.


We have isolated human cDNA clones for USF2, a new member of the upstream stimulatory factor (USF) family of transcription factors. Analysis of these clones revealed the existence of highly conserved elements in the C terminal region of all USF proteins. These include the basic region, helix-loop-helix (HLH) motif, and, in the case of the human proteins, the C-terminal leucine repeat (LR). In addition, a highly conserved USF-specific domain is located immediately upstream of the basic region. Using in vitro translated proteins, we found that all members of the USF family bound DNA as dimers. The N-terminal portion of USF, including the USF-specific domain, was entirely dispensable for dimer formation and DNA-binding. However, deletion mutants of USF2 lacking the LR were deficient in DNA-binding activity. Interestingly, each of the USF proteins could form functional heterodimers with the other family members, including the sea urchin USF, which does not have a LR motif. This indicates that the conserved LR in human USF is not required for dimer formation, and influences only indirectly DNA-binding.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • DNA / metabolism*
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Gene Expression
  • Genes
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Multigene Family
  • Protein Conformation
  • Recombinant Fusion Proteins / metabolism
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Upstream Stimulatory Factors


  • DNA-Binding Proteins
  • Recombinant Fusion Proteins
  • Transcription Factors
  • USF1 protein, human
  • USF2 protein, human
  • Upstream Stimulatory Factors
  • DNA

Associated data

  • GENBANK/M79310
  • GENBANK/M81117
  • GENBANK/M81118
  • GENBANK/M86369
  • GENBANK/M86370
  • GENBANK/M90413
  • GENBANK/M90414
  • GENBANK/S50537
  • GENBANK/X65112
  • GENBANK/X65113