Abstract
In vitro, the TAFII60 component of the TFIID complex contributes to RNA polymerase II transcription initiation by serving as a coactivator that interacts with specific activator proteins and possibly as a promoter selectivity factor that interacts with the downstream promoter element. In vivo roles for TAFII60 in metazoan transcription are not as clear. Here we have investigated the developmental and transcriptional requirements for TAFII60 by analyzing four independent Drosophila melanogaster TAF II 60 mutants. Loss-of-function mutations in Drosophila TAF II 60 result in lethality, indicating that TAFII60 provides a nonredundant function in vivo. Molecular analysis of TAF II 60alleles revealed that essential TAFII60 functions are provided by two evolutionarily conserved regions located in the N-terminal half of the protein. TAFII60 is required at all stages of Drosophila development, in both germ cells and somatic cells. Expression of TAFII60 from a transgene rescued the lethality of TAF II 60mutants and exposed requirements for TAFII60 during imaginal development, spermatogenesis, and oogenesis. Phenotypes of rescued TAF II 60 mutant flies implicate TAFII60 in transcriptional mechanisms that regulate cell growth and cell fate specification and suggest that TAFII60 is a limiting component of the machinery that regulates the transcription of dosage-sensitive genes. Finally, TAFII60 plays roles in developmental regulation of gene expression that are distinct from those of other TAFIIproteins.
ACKNOWLEDGMENTS
We thank Henry Chang, Felix Karim, Marc Therrien, and Gerald Rubin for their assistance characterizing the TAF II 60XS922 allele, Jim Kennison for generously providing the TAF II 601 , TAF II 602 , andTAF II 603 alleles, Erin Schlag for assistance sequencing the TAF II 60 alleles, Robert Tjian for providing TAFII60 antibody, Tom Burke and Jim Kadonaga for providing eTBP flies, and Sue Haynes for assistance analyzing the spermatogenesis defect. N. A. was supported by a fellowship from the Japan Society for the Promotion of Science. This work was supported by the Intramural Program in the National Institute of Child Health and Human Development.