Apoptosis is induced in BHK cells by the tsBN462/13 mutation in the CCG1/TAF_II250 subunit of the TFIID basal transcription factor

A temperature-sensitive (ts) mutant of the BHK21 cell line derived from golden hamsters, tsBN462 has a mutation in the gene encoding the largest subunit of the TFIID complex, TAF_II250/p230/CCG1, and arrests in the G1 phase at the nonpermissive temperature, 39.5°C. We found that tsBN462 cells underwent apoptosis following growth arrest at 39.5°C, suggesting a role for CCG1 as a repressor of apoptosis. By electron microscopic observation, tsBN462 cells at 39.5°C showed characteristic features of apoptosis. Apoptosis was not suppressed by expression of Bcl-2 or the adenovirus E1B 19 kDa protein. Cell death was suppressed completely by expression of wild-type CCG1 and partially by wild-type p53, a growth suppressor protein. Cell cycle arrest induced by p53 may help survival of tsBN462 cells at 39.5°C. Apoptosis was accelerated in SV4O large T antigen-transformed tsBN462 cells at 39.5°C where SV40 large T antigen formed a complex with p53, implying that the apoptosis of tsBN462 cells at 39.5°C occurred in a p53-independent manner. Our results suggest that CCG1/TAF_II250 is required for the expression of factors regulating apoptosis.