Segments of the POU domain influence one another's DNA-binding specificity.
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.
Aurora
R
R
Cold Spring Harbor Laboratory, New York 11724-2206.
Herr
W
W
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004586:Electrophoresis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D051863:Host Cell Factor C1; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D050811:Octamer Transcription Factor-1; D050814:Octamer Transcription Factor-3; D010957:Plasmids / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051863:Host Cell Factor C1; D046911:Macromolecular Substances; D050811:Octamer Transcription Factor-1; D050814:Octamer Transcription Factor-3; D011993:Recombinant Fusion Proteins; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D004247:DNA