Sinha Ishani, Kumar Shambhu, Poonia Poonam, Sawhney Sonal, Natarajan Krishnamurthy
From the Laboratory of Eukaryotic Gene Regulation, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
From the Laboratory of Eukaryotic Gene Regulation, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India
J Biol Chem. 2017 Apr 14;292(15):6047-6055. doi: 10.1074/jbc.C116.768549. Epub 2017 Mar 8.
TATA box-binding protein (TBP)-associated factors (TAFs), evolutionarily conserved from yeast to humans, play a central role during transcription initiation. A subset of TAF proteins is shared in transcription factor II D (TFIID) and SAGA transcription regulatory complexes. Although higher eukaryotes contain multiple TAF variants that specify tissue- and developmental stage-specific organization of TFIID or SAGA complexes, in unicellular genomes, however, each TAF is encoded by a single gene. Surprisingly, we found that the genome of , the predominant human fungal pathogen, contains two paralogous genes, and , encoding H2B-like histone-fold domain-containing variants. Of the available fungal genome sequences, only seven other closely related diploid pathogenic genomes encode the two paralogs. Using affinity purifications from cell extracts, we demonstrate that CaTAF12L uniquely associates with the SAGA complex and CaTAF12 associates with the TFIID complex. We further show that , but not , is essential for growth. Conditional depletion of the two TAF12 variant proteins caused distinct cellular and colony phenotypes. Together our results define a specialized organization of the TAF12 variants and non-redundant roles for the two variants in the unicellular genome.
TATA 框结合蛋白（TBP）相关因子（TAFs）在进化上从酵母到人类都保持保守，在转录起始过程中起核心作用。一部分TAF蛋白在转录因子 II D（TFIID）和SAGA转录调控复合物中共享。虽然高等真核生物含有多种TAF变体，这些变体决定了TFIID或SAGA复合物的组织特异性和发育阶段特异性，但在单细胞基因组中，每个TAF由单个基因编码。令人惊讶的是，我们发现人类主要真菌病原体白色念珠菌的基因组包含两个同源基因CaTAF12L和CaTAF12，它们编码含H2B样组蛋白折叠结构域的变体。在现有的真菌基因组序列中，只有其他七个密切相关的二倍体致病白色念珠菌基因组编码这两个同源物。通过从白色念珠菌细胞提取物中进行亲和纯化，我们证明CaTAF12L仅与SAGA复合物相关联，而CaTAF12与TFIID复合物相关联。我们进一步表明，CaTAF12L对白色念珠菌生长至关重要，而CaTAF12并非如此。这两种TAF12变体蛋白的条件性缺失导致了不同的细胞和菌落表型。我们的结果共同定义了TAF12变体的特殊组织方式，以及这两种变体在单细胞白色念珠菌基因组中的非冗余作用。
