DIFFERENTIAL REGULATION OF TRANSCRIPTION OF P21 AND CYCLIN D1 CONFERRED BY TAF(II)250

The TATA-binding protein-associated factor TAF(II)250, the largest sub unit of TFIID, was first identified as the cell cycle regulatory prote in CCG1, The ts13 Syrian hamster ovary fibroblast cell line, which con tains a temperature-sensitive point mutation in TAF(II)250/CCG1, is ar rested in G(1) following a shift to the nonpermissive temperature. Her e we demonstrate that the level of the D-type cyclins, in particular D 1, was reduced, whereas the level of the cyclin-dependent kinase inhib itor p21 was stimulated in ts13 cells at the nonpermissive temperature . The levels of expression of cyclins A and E were not affected by tem perature shift, We further show that at least part of the regulation o f D1 and p21 levels in ts13 cells is mediated at the level of transcri ption initiation, These results suggest that the effect of the tempera ture-sensitive mutation TAF(II)250 on cell growth can be mediated thro ugh the differential regulation of transcription of specific cell grow th regulatory genes, such as cyclin D1 and p21.