Segments of the POU domain influence one another's DNA-binding specificity

Mol Cell Biol. 1992 Feb;12(2):455-67. doi: 10.1128/mcb.12.2.455-467.1992.

Abstract

The ubiquitously expressed mammalian POU-domain protein Oct-1 specifically recognizes two classes of cis-acting regulatory elements that bear little sequence similarity, the octamer motif ATGCAAAT and the TAATGARAT motif. The related pituitary-specific POU protein Pit-1 also recognizes these two motifs but, unlike Oct-1, binds preferentially to the TAATGARAT motif. Yet in our assay, Pit-1 still binds octamer elements better than does the octamer motif-binding protein Oct-3. The POU domain is responsible for recognizing these diverse regulatory sequences through multiple DNA contacts that include the two POU subdomains, the POU-specific region, and the POU homeodomain. The DNA-binding properties of 10 chimeric POU domains, in which different POU-domain segments are derived from either Oct-1 or Pit-1, reveal a high degree of structural plasticity; these hybrid proteins all bind DNA well and frequently bind particular sites better than does either of the parental POU domains. In these chimeric POU domains, the POU-specific A and B boxes and the hypervariable POU linker can influence DNA-binding specificity. The surprising result is that the influence a particular segment has on DNA-binding specificity can be greatly affected by the origin of other segments of the POU domain and the sequence of the binding site. Thus, the broad but selective DNA-binding specificity of Oct-1 is conferred both by multiple DNA contacts and by dynamic interactions within the DNA-bound POU domain.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Binding Sites
  • DNA / metabolism*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Electrophoresis
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression
  • Host Cell Factor C1
  • Macromolecular Substances
  • Molecular Sequence Data
  • Octamer Transcription Factor-1
  • Octamer Transcription Factor-3
  • Plasmids / genetics
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Regulatory Sequences, Nucleic Acid*
  • Transcription Factor Pit-1
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*

Substances

  • DNA-Binding Proteins
  • Host Cell Factor C1
  • Macromolecular Substances
  • Octamer Transcription Factor-1
  • Octamer Transcription Factor-3
  • Recombinant Fusion Proteins
  • Transcription Factor Pit-1
  • Transcription Factors
  • DNA