Developmental and Transcriptional Consequences of Mutations in Drosophila TAF II 60

Abstract

ABSTRACT In vitro, the TAF II 60 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 TAF II 60 in metazoan transcription are not as clear. Here we have investigated the developmental and transcriptional requirements for TAF II 60 by analyzing four independent Drosophila melanogaster TAF II 60 mutants. Loss-of-function mutations in Drosophila TAF II 60 result in lethality, indicating that TAF II 60 provides a nonredundant function in vivo. Molecular analysis of TAF II 60 alleles revealed that essential TAF II 60 functions are provided by two evolutionarily conserved regions located in the N-terminal half of the protein. TAF II 60 is required at all stages of Drosophila development, in both germ cells and somatic cells. Expression of TAF II 60 from a transgene rescued the lethality of TAF II 60 mutants and exposed requirements for TAF II 60 during imaginal development, spermatogenesis, and oogenesis. Phenotypes of rescued TAF II 60 mutant flies implicate TAF II 60 in transcriptional mechanisms that regulate cell growth and cell fate specification and suggest that TAF II 60 is a limiting component of the machinery that regulates the transcription of dosage-sensitive genes. Finally, TAF II 60 plays roles in developmental regulation of gene expression that are distinct from those of other TAF II proteins.