Howard Hughes Medical Institute and Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, California Institute for Regenerative Medicine Center of Excellence, University of California, Berkeley, CA 94720.
Proc Natl Acad Sci U S A. 2013 Oct 15;110(42):16886-91. doi: 10.1073/pnas.1317034110. Epub 2013 Sep 30.
TATA-binding protein (TBP)-associated factor 7l (Taf7l; a paralogue of Taf7) and TBP-related factor 2 (Trf2) are components of the core promoter complex required for gene/tissue-specific transcription of protein-coding genes by RNA polymerase II. Previous studies reported that Taf7l knockout (KO) mice exhibit structurally abnormal sperm, reduced sperm count, weakened motility, and compromised fertility. Here we find that continued backcrossing of Taf7l(-/Y) mice from N5 to N9 produced KO males that are essentially sterile. Genome-wide expression profiling by mRNA-sequencing analysis of wild-type (WT) and Taf7l(-/Y) (KO) testes revealed that Taf7l ablation impairs the expression of many postmeiotic spermatogenic-specific as well as metabolic genes. Importantly, histological analysis of testes revealed that Taf7l(-/Y) mice develop postmeiotic arrest at the first stage of spermiogenesis, phenotypically similar to Trf2(-/-) mice, but distinct from Taf4b(-/-) mice. Indeed, we find that Taf7l and Trf2 coregulate postmeiotic genes, but none of Taf4b-regulated germ stem cell genes in testes. Genome-wide ChIP-sequencing studies indicate that TAF7L binds to promoters of activated postmeiotic genes in testis. Moreover, biochemical studies show that TAF7L associates with TRF2 both in vitro and in testis, suggesting that TAF7L likely cooperates directly with TRF2 at promoters of a subset of postmeiotic genes to regulate spermiogenesis. Our findings thus provide a previously undescribed mechanism for cell-type-specific transcriptional control involving an interaction between a "nonprototypic" core promoter recognition factor (Trf2) and an orphan TAF subunit (Taf7l) in mammalian testis-specific gene transcription.
TATA 结合蛋白（TBP）相关因子 7l（Taf7l；Taf7 的同源物）和 TBP 相关因子 2（Trf2）是核心启动复合物的组成部分，该复合物是 RNA 聚合酶 II 对蛋白编码基因进行组织特异性转录所必需的。先前的研究表明，Taf7l 敲除（KO）小鼠表现出结构异常的精子、精子数量减少、运动能力减弱和生育能力受损。在这里，我们发现将 Taf7l(-/Y) 小鼠从 N5 代连续回交到 N9 代产生的 KO 雄性小鼠基本上是不育的。通过对野生型（WT）和 Taf7l(-/Y)（KO）睾丸的 mRNA 测序分析进行全基因组表达谱分析，发现 Taf7l 缺失会损害许多减数后精子发生特异性和代谢基因的表达。重要的是，睾丸的组织学分析表明，Taf7l(-/Y) 小鼠在精子发生的第一阶段发生减数后停滞，表型类似于 Trf2(-/-) 小鼠，但与 Taf4b(-/-) 小鼠不同。事实上，我们发现 Taf7l 和 Trf2 共同调节减数后基因，但在睾丸中没有 Taf4b 调节的生殖干细胞基因。全基因组 ChIP-seq 研究表明，TAF7L 结合到睾丸中激活的减数后基因的启动子上。此外，生化研究表明 TAF7L 在体外和睾丸中均与 TRF2 结合，表明 TAF7L 可能直接在一组减数后基因的启动子上与 TRF2 合作，以调节精子发生。我们的研究结果因此提供了一种以前未描述的机制，涉及一种“非典型”核心启动子识别因子（Trf2）和一种孤儿 TAF 亚基（Taf7l）之间的相互作用，用于哺乳动物睾丸特异性基因转录的细胞类型特异性转录控制。
