PROMOTER-SELECTIVE TRANSCRIPTIONAL DEFECT IN CELL-CYCLE MUTANT TS13 RESCUED BY HTAF(II)250

The TAF(II)250 subunit of the human transcription factor IID (TFIID) rescues the temperature-sensitive hamster cell line ts13 and overcomes a G1 arrest. Investigation of the transcriptional properties of ts13 nuclear extracts in vitro showed that activation by the site-specific regulators Sp1 and Gal4VP16 is temperature sensitive in ts13 extracts, whereas basal transcription remains unaffected. This transcriptional defect can be rescued by purified human TFIID or by expression of wild-type TAF(II)250 in ts13 cells. Expression from the cyclin A but not c-fos promoter is temperature sensitive in these mutant cells. Thus, the mutation in TAF(II)250 appears to have gene-specific effects that may lead to the ts13 cell cycle phenotype.