Université Paris-Sud, Institut de Génétique et Microbiologie UMR8621, Orsay, France.
PLoS Genet. 2013;9(7):e1003642. doi: 10.1371/journal.pgen.1003642. Epub 2013 Jul 18.
High-mobility group (HMG) B proteins are eukaryotic DNA-binding proteins characterized by the HMG-box functional motif. These transcription factors play a pivotal role in global genomic functions and in the control of genes involved in specific developmental or metabolic pathways. The filamentous ascomycete Podospora anserina contains 12 HMG-box genes. Of these, four have been previously characterized; three are mating-type genes that control fertilization and development of the fruit-body, whereas the last one encodes a factor involved in mitochondrial DNA stability. Systematic deletion analysis of the eight remaining uncharacterized HMG-box genes indicated that none were essential for viability, but that seven were involved in the sexual cycle. Two HMG-box genes display striking features. PaHMG5, an ortholog of SpSte11 from Schizosaccharomyces pombe, is a pivotal activator of mating-type genes in P. anserina, whereas PaHMG9 is a repressor of several phenomena specific to the stationary phase, most notably hyphal anastomoses. Transcriptional analyses of HMG-box genes in HMG-box deletion strains indicated that PaHMG5 is at the hub of a network of several HMG-box factors that regulate mating-type genes and mating-type target genes. Genetic analyses revealed that this network also controls fertility genes that are not regulated by mating-type transcription factors. This study points to the critical role of HMG-box members in sexual reproduction in fungi, as 11 out of 12 members were involved in the sexual cycle in P. anserina. PaHMG5 and SpSte11 are conserved transcriptional regulators of mating-type genes, although P. anserina and S. pombe diverged 550 million years ago. Two HMG-box genes, SOX9 and its upstream regulator SRY, also play an important role in sex determination in mammals. The P. anserina and S. pombe mating-type genes and their upstream regulatory factor form a module of HMG-box genes analogous to the SRY/SOX9 module, revealing a commonality of sex regulation in animals and fungi.
高迁移率族（HMG）B 蛋白是真核生物 DNA 结合蛋白，其特征是具有 HMG 盒功能基序。这些转录因子在全局基因组功能以及控制参与特定发育或代谢途径的基因中发挥关键作用。丝状子囊菌 Podospora anserina 含有 12 个 HMG 盒基因。其中，有 4 个先前已被表征；三个是控制果实体受精和发育的交配型基因，而最后一个编码与线粒体 DNA 稳定性有关的因子。对其余 8 个未表征的 HMG 盒基因的系统缺失分析表明，它们都不是生存所必需的，但其中 7 个与有性周期有关。两个 HMG 盒基因具有显著特征。PaHMG5 是 Schizosaccharomyces pombe 中的 SpSte11 的直系同源物，是 P. anserina 中交配型基因的关键激活因子，而 PaHMG9 是几个与静止期有关的现象的抑制剂，尤其是菌丝吻合。在 HMG 盒缺失菌株中的 HMG 盒基因的转录分析表明，PaHMG5 是调节交配型基因和交配型靶基因的几个 HMG 盒因子网络的中心。遗传分析表明，该网络还控制不受交配型转录因子调节的育性基因。这项研究表明，HMG 盒成员在真菌的有性生殖中起着至关重要的作用，因为在 P. anserina 中，12 个成员中有 11 个参与了有性周期。PaHMG5 和 SpSte11 是交配型基因的保守转录调节剂，尽管 P. anserina 和 S. pombe 在 5.5 亿年前就已经分化。两个 HMG 盒基因，SOX9 及其上游调节剂 SRY，也在哺乳动物的性别决定中发挥重要作用。P. anserina 和 S. pombe 的交配型基因及其上游调节因子形成了类似于 SRY/SOX9 模块的 HMG 盒基因模块，揭示了动物和真菌中性别调控的共同性。
