Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
Mol Microbiol. 2011 Nov;82(3):602-18. doi: 10.1111/j.1365-2958.2011.07837.x. Epub 2011 Oct 10.
Efg1 is a central transcriptional regulator of morphogenesis and metabolism in Candida albicans. In vivo genome-wide ChIP chip and in vitro footprint analyses revealed the Efg1 recognition sequence (EGR-box) TATGCATA in the yeast growth form of this human fungal pathogen. Upstream regions of EFG1 and genes encoding transcriptional regulators of hyphal growth including TCC1, CZF1, TEC1, DEF1 and NRG1 contained EGR- and/or EGR-like boxes. Unexpectedly, after brief hyphal induction the genome-wide Efg1 binding pattern was completely altered and new binding sites of yet unknown specificity had appeared. Hyphal induction abolished Efg1 accumulation on EFG1 and TCC1 promoters and led to rapid decline of both transcripts, although the Efg1 protein persisted in cells. While EFG1 promoter activity in the yeast growth form did not depend on bound Efg1, its downregulation under hyphal induction depended on the presence of Efg1 and the protein kinase A isoform Tpk2. Deletion analyses of the EFG1 upstream region revealed that none of its resident EGR-boxes is uniquely responsible for EFG1 promoter downregulation. These results suggest different binding specificities of Efg1 in yeast growth and in hyphal induction and suggest a brief time window following hyphal induction, in which Efg1 exerts its repressive effect on target promoters.
Efg1 是白念珠菌形态发生和代谢的核心转录调节剂。体内全基因组 ChIP 芯片和体外足迹分析揭示了这种人类真菌病原体酵母生长形式的 Efg1 识别序列（EGR-盒）TATGCATA。EFG1 和菌丝生长转录调节剂基因（包括 TCC1、CZF1、TEC1、DEF1 和 NRG1）的上游区域包含 EGR-和/或 EGR 样框。出乎意料的是，短暂的菌丝诱导后，Efg1 的全基因组结合模式完全改变，出现了新的特异性结合位点。菌丝诱导消除了 Efg1 在 EFG1 和 TCC1 启动子上的积累，并导致两个转录本的快速下降，尽管 Efg1 蛋白在细胞中持续存在。虽然酵母生长形式的 EFG1 启动子活性不依赖于结合的 Efg1，但在菌丝诱导下其下调依赖于 Efg1 和蛋白激酶 A 同工型 Tpk2 的存在。EFG1 上游区域的缺失分析表明，其驻留的 EGR 框都不能单独负责 EFG1 启动子的下调。这些结果表明 Efg1 在酵母生长和菌丝诱导中具有不同的结合特异性，并表明在菌丝诱导后的短暂时间窗口内，Efg1 对靶启动子发挥其抑制作用。
