Aoyagi N, Wassarman D A
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Mol Cell Biol. 2001 Oct;21(20):6808-19. doi: 10.1128/MCB.21.20.6808-6819.2001.
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.
在体外，TFIID复合物的TAF（II）60组分作为一种共激活因子与特定激活蛋白相互作用，可能还作为一种与下游启动子元件相互作用的启动子选择性因子，从而有助于RNA聚合酶II转录起始。TAF（II）60在多细胞动物转录中的体内作用尚不清楚。在这里，我们通过分析四个独立的果蝇TAF（II）60突变体，研究了TAF（II）60的发育和转录需求。果蝇TAF（II）60的功能丧失突变导致致死性，表明TAF（II）60在体内提供了一种非冗余功能。对TAF（II）60等位基因的分子分析表明，TAF（II）60的基本功能由位于该蛋白质N端一半的两个进化保守区域提供。在果蝇发育的所有阶段，生殖细胞和体细胞中都需要TAF（II）60。来自转基因的TAF（II）60表达挽救了TAF（II）60突变体的致死性，并揭示了在成虫发育、精子发生和卵子发生过程中对TAF（II）60的需求。挽救后的TAF（II）60突变体果蝇的表型表明，TAF（II）60参与了调节细胞生长和细胞命运决定的转录机制，并表明TAF（II）60是调节剂量敏感基因转录的机制中的一个限制组分。最后，TAF（II）60在基因表达的发育调控中发挥的作用与其他TAF（II）蛋白不同。
