Distinct requirements for C-elegans TAF(II)s in early embryonic transcription

TAF(II)s are conserved components of the TFIID, TFTC and SAGA-related mRNA transcription complexes. In yeast (y), yTAF(II)17 is required broadly for t ranscription, but various other TAF(II)s appear to have more specialized fu nctions. It is important to determine how TAF(II)s contribute to transcript ion in metazoans, which have larger and more diverse genomes. We have exami ned TAF(II) functions in early Caenorhabditis elegans embryos, which can su rvive without transcription for several cell generations. We show that taf- 10 (yTAF(II)7) and taf-11 (yTAF(II)25) are required for a significant fract ion of transcription, but apparently are not needed for expression of multi ple developmental and other metazoan-specific genes. In contrast, taf-5 (yT AF(II)48; human TAF(II)130) seems to be required for essentially all early embryonic mRNA transcription. We conclude that TAF-10 and TAF-11 have modul ar functions in metazoans, and can be bypassed at many metazoan-specific ge nes. The broad involvement of TAF-5 in mRNA transcription in vivo suggests a requirement for either TFIID or a TFTC-like complex.