The TFIID components human TAF(II)140 and Drosophila BIP2 (TAF(II)155) arenovel metazoan homologues of yeast TAF(II)47 containing a histone fold anda PHD finger

The RNA polymerase II transcription factor TFIID comprises the TATA binding protein (TBP) and a set of TBP-associated factors (TAF(II)s). TFIID has be en extensively characterized for yeast, Drosophila, and humans, demonstrati ng a high degree of conservation of both the amino acid sequences of the co nstituent TAF(II)s and overall molecular organization. In recent years, it has been assumed that all the metazoan TAF(II)s have been identified, yet n o metazoan homologues of yeast TAF(II)47 (yTAF(II)47) and yTAF(II)25 are kn own. Both of these yTAF(II)s contain a histone fold domain (HFD) which sele ctively heterodimerizes with that of yTAF(II)25. We have cloned a novel mou se protein, TAF(II)140, containing an HFD and a plant homeodomain (PHD) fin ger, which we demonstrated by immunoprecipitation to be a mammalian TFIID c omponent. TAF(II)140 shows extensive sequence similarity to Drosophila BIP2 (dBIP2) (dTAF(II)155), which we also show to be a component of Drosophila TFIID. These proteins are metazoan homologues of yTAF(II)47 as their HFDs s electively heterodimerize with dTAF(II)24 and human TAF(II)30, metazoan hom ologues of yTAF(II)25. We further show that yTAF(II)65 shares two domains w ith the Drosophila Prodos protein, a recently described potential dTAF(II). These conserved domains are critical for yTAF(II)65 function in vivo. Our results therefore identify metazoan homologues of yTAF(II)47 and yTAF(II)65 .