裂殖酵母SAGA各亚基亚细胞荧光定位分析

Subcellular fluorescence localization analysis of all SAGA subunits in fission yeast(Schizosaccharomyces pombe)

SAGA(Spt-Ada-Gcn5 Acetyltransferase complex)是一个多亚基保守的转录复合物,在裂殖酵母(Schizosaccharomyces pombe)里由19个亚基组成,调控体内10%基因的转录。文章通过构建原位整合荧光菌株,完整地分析了SAGA所有亚基的亚细胞荧光定位。荧光数据显示这些亚基的定位可分为4种类型,提示SAGA亚基除共同参与转录调控之外,可能还有其他功能。SAGA亚基Sgf73是联系去泛素化模块与SAGA其他模块的桥梁,它的缺失不仅明显减少了去泛素化亚基Ubp8、Sgf11、Sus1核内的定位,同时也影响了乙酰化亚基Gcn5、Sgf29、Ngg1以及核心结构亚基Spt7在细胞核内的定位,这提示Sgf73对维持SAGA的酶学功能和稳定性至关重要。另外,sgf73+的缺失还造成了胞质分裂的缺陷,导致细胞出现多核多膈膜表型。在△sgf73里过量表达膈膜降解途径中的关键基因ace2+和mid2+的回补结果表明,ace2+不能回补sgf73+缺失造成的缺陷,而mid2+也仅能部分回补,提示Sgf73可能还通过其他途径影响了胞质分裂。

SAGA（Spt-Ada-Gcn5 Acetyltransferase complex） is a multi-subunit and conservative transcription complex, which is composed of 19 subunits in fission yeast and regulates the transcription of 10% genes in vivo. Through construct ing in situ integrated fluorescence strains, we analyzed subcellular fluorescence localization of all SAGA subunits. Micro scopic data showed localization manners could be sorted by 4 types, suggesting that these SAGA subunits may have addi tional functions besides transcriptional regulation. Subunit Sgf73 is the bridge that connects deubiquitination module and other SAGA modules, lacking of sg173＋ not only significantly reduced nuclear fluorescence localization （NFL） of deubiquitination subunits Ubp8, Sgfl 1, Sus 1, but also affected NFL of acetylation subnnits Gcn5, Sgf29, Ngg 1, and the core structure subunit Spt7.The impact indicates that Sgf73 is important to maintain enzymatic function and stabilization of SAGA. Moreover, deletion of sg[73＋ also caused a cytokinesis defect, which is characterized by a multi-nucleus and mul ti-septum phenotype. Overexpressing ace2＋ and mid2＋ in △sgf73, which are key genes involved in septum degradation,showed that ace2＋ could not rescue the defect, and mid2~ could only partially compensate for the deficiency, suggesting that Sgf73 may play a role in other pathways that affect cytokinesis.