DIRECT CLONING OF LEUCINE ZIPPER PROTEINS - JUN BINDS COOPERATIVELY TO THE CRE WITH CRE-BP1

  • 1 April 1990
    • journal article
    • research article
    • Vol. 5  (4) , 451-458
Abstract
The proto-oncogene products Fos and Jun form a stable heterodimeric complex that functions in transcriptional regulation by interacting with the DNA sequence known as the AP-1 site. Dimer formation occurs through the leucine zipper, a structural motif involving a heptad repeat of leucine residues there is conserved in several fos- and jun-related genes. We have employed a novel cloning strategy to isolate genes encoding proteins capable of forming complexes with Jun. The procedure involves direct screening of a .lambda.gt11 cDNA library with with a biotinylated Jun polypeptide. One clone isolated in this manner encodes CRE-BP1, a leucine zipper-containing protein that binds to the cyclic AMP response element (CRE) as a homodimer. CRE-BPI also forms heterodimeters with Jun but not with Fos. Jun binds cooperatively to the CRE in association with CRE-BP1. Thus, the DNA-binding specificity and affinity of Jun are modulated by association with Fos or with CRE-BP1.