SEQUENCE OF CDNAS ENCODING COMPONENTS OF VASCULAR ACTIN SINGLE-STRANDED DNA-BINDING FACTOR-2 ESTABLISH IDENTITY TO PUR-ALPHA AND PUR-BETA

Transcriptional repression of the mouse vascular smooth muscle cu-acti n gene in fibroblasts and myoblasts is mediated, in part, by the inter action of two single-stranded DNA binding activities with opposite str ands of an essential transcription enhancer factor-1 recognition eleme nt (Sun, S., Stoflet, E. S., Cogan, J. G., Strauch, A. R., and Getz, M . J. (1995) Mol. Cell. Biol. 15, 2429-2436). One of these activities, previously designated vascular actin single-stranded DNA-binding facto r 2 includes two distinct polypeptides (p44 and p46) which specificall y interact with the purine rich strand of both the enhancer and a rela ted element in a protein coding exon of the gene (Kelm, R. J., Jr., Su n, S., Strauch, A. R., and Getz, M. J. (1996) J. Biol. Chem. 271, 2427 8-24285). Expression screening of a mouse lung cDNA library with a vas cular actin single-stranded DNA-binding factor 2 recognition element h as now resulted in the isolation of two distinct cDNA clones that enco de p46 and p44, One of these proteins is identical to Pur alpha, a ret inoblastoma-binding; protein previously implicated in both transcripti onal activation and DNA replication, The other is a related family mem ber, presumably Pur beta, Comparative band shift and Southwestern blot analyses conducted with cellular p46, p44, and cloned Pur proteins sy nthesized in vitro and in vivo, establish identity of p46 with Pur alp ha and p44 with Pur beta. This study implicates Pur alpha and/or Pur b eta in the control of vascular smooth muscle alpha-actin gene transcri ption.