Two WD repeat-containing TATA-binding protein-associated factors in fission yeast that suppress defects in the anaphase-promoting complex

The general transcription factor IID consists of the TATA-binding protein ( TBP) and multiple TBP-associated factors (TAFs). Here we report the isolati on of two related TAF genes from the fission yeast Schizosaccha romyces pom be as multicopy suppressors of a temperature-sensitive mutation in the ubiq uitin-conjugating enzyme gene ubcP4(+). The ubcP4(ts) mutation causes cell cycle arrest in mitosis, probably due to defects in ubiquitination mediated by the anaphase-promoting complex/cyclosome. One multicopy suppressor is t he previously reported gene taf72(+), whereas the other is a previously uni dentified gene named taf73(+). We show that the taf73(+) gene, like taf72(), is essential for cell viability. The taf72(+) and taf73(+) genes encode proteins homologous to WD repeat-containing TAFs such as human TAF100, Dros ophila TAF80/85, and Saccharomyces cerevisiae TAF90, We demonstrate that TA F72 and TAF73 proteins are present in the same complex with TBP and other T AFs and that TAF72, but not TAF73, is associated with the putative histone acetylase Gcn5, We also show that overexpression of TAF72 or TAF73 suppress es the cell cycle arrest in mitosis caused by a mutation in the anaphase-pr omoting complex/cyclosome subunit gene cut9(+), These results suggest that TAF72 and TAF73 may regulate the expression of genes involved in ubiquitin- dependent proteolysis during mitosis. Our study thus provides evidence for a possible role of WD repeat-containing TAFs in the expression of genes inv olved in progression through the M phase of the cell cycle.