Developmental and transcriptional consequences of mutations in Drosophila TAF(II)60

In vitro, the TAF(II)60 component of the TFIID complex contributes to RNA p olymerase II transcription initiation by serving as a coactivator that inte racts with specific activator proteins and possibly as a promoter selectivi ty factor that interacts with the downstream promoter element. In vivo role s for TAF(II)60 in metazoan transcription are not as clear. Here we have in vestigated the developmental and transcriptional requirements for TAF(II)60 by analyzing four independent Drosophila melanogaster TAF(II)60 mutants. L oss-of-function mutations in Drosophila TAF(II)60 result in lethality, indi cating that TAF(II)60 provides a nonredundant function in vivo. Molecular a nalysis of TAF(II)60 alleles revealed that essential TAF(II)60 functions ar e provided by two evolutionarily conserved regions located in the N-termina l half of the protein. TAF(II)60 is required at all stages of Drosophila de velopment, in both germ cells and somatic cells. Expression of TAF(II)60 fr om a transgene ;rescued the lethality of TAF(II)60 mutants and exposed requ irements for TAF(II)60 during imaginal development, spermatogenesis, and oo genesis. Phenotypes of rescued TAF(II)60 mutant flies implicate TAF(II)60 i n transcriptional mechanisms that regulate cell growth and cell fate specif ication and suggest that TAF(II)60 is a limiting component of the machinery that regulates the transcription of dosage-sensitive genes. Finally, TAF(I I)60 plays roles in developmental regulation of gene expression that are di stinct from those of other TAF(II) proteins.