The cell-specific transcription factor PTF1 contains two different subunits that interact with the DNA. (original) (raw)

  1. E Roux,
  2. M Strubin,
  3. O Hagenbüchle, and
  4. P K Wellauer
  5. Swiss Cancer Research Institute, Epalinges, Switzerland.

Abstract

The cognate sequence of transcription factor PTF1, which plays a key role in pancreas-specific gene expression, has a bipartite organization. Two separate DNA domains, the A and the B boxes, are required for efficient binding of the factor. The structure of PTF1 was elucidated by cross-linking purified PTF1 to DNA templates that had been differentially substituted with azido-deoxyuridine (N3.dU). This site-directed UV cross-linking shows that PTF1 contains two DNA-binding proteins, distinct in size and sensitivity to Staphylococcus aureus V8 protease. A 64-kD protein is cross-linked with DNA containing N3.dU substitutions in the A box, and a 48-kD protein is cross-linked with DNA containing N3.dU substitutions in the B box. Both proteins bind simultaneously to the same DNA molecule. The data indicate that PTF1 is a heteromeric oligomer and that its cell-specific DNA-binding potential is the result of a concerted activity of two DNA-binding subunits.

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