Institute of Microbiology and Genetics, Genetics of Eukaryotic Microorganisms, Georg-August University, Grisebachstraße 8, D-37077 Göttingen, Germany.
Eur J Cell Biol. 2010 Dec;89(12):873-87. doi: 10.1016/j.ejcb.2010.06.014. Epub 2010 Aug 10.
In fungi, the homoeodomain protein STE12 controls diverse developmental processes, and derives its regulatory specificity from different protein interactions. We recently showed that in the homothallic ascomycete Sordaria macrospora, STE12 is essential for ascospore development, and is able to interact with the alpha-domain mating-type protein SMTA-1 and the MADS box protein MCM1. To further evaluate the functional roles of STE12, we used the yeast two-hybrid approach to identify new STE12-interacting partners. Using STE12 as bait, a small, serine-threonine-rich protein (designated STE12-interacting protein 2, SIP2) was identified. SIP2 is conserved among members of the fungal class Sordariomycetes. In vivo localization studies revealed that SIP2 was targeted to the nucleus and cytoplasm. The STE12/SIP2 interaction was further confirmed in vivo by bimolecular fluorescence complementation. Nuclear localization of SIP2 was apparently mediated by STE12. Unlike deletion of ste12, deletion of sip2 in S. macrospora led to only a slight decrease in ascospore germination, and no other obvious morphological phenotype. In comparison to the Δste12 single knockout strain, ascospore germination was significantly increased in a Δsip2/ste12 double knockout strain. Our data provide evidence for a regulatory role of the novel fungal protein SIP2 in ascospore germination.
在真菌中，同源域蛋白 STE12 控制着多种发育过程，其调节特异性来自于不同的蛋白质相互作用。我们最近表明，在同宗结合的子囊菌 Sordaria macrospora 中，STE12 对于子囊孢子的发育是必需的，并且能够与α-结构域交配型蛋白 SMTA-1 和 MADS 盒蛋白 MCM1 相互作用。为了进一步评估 STE12 的功能作用，我们使用酵母双杂交方法来鉴定新的 STE12 相互作用伙伴。使用 STE12 作为诱饵，鉴定到一个小的、丝氨酸-苏氨酸丰富的蛋白（命名为 STE12 相互作用蛋白 2，SIP2）。SIP2 在真菌 Sordariomycetes 类成员中是保守的。体内定位研究表明 SIP2 被靶向到细胞核和细胞质。STE12/SIP2 相互作用在体内通过双分子荧光互补进一步得到证实。SIP2 的核定位显然是由 STE12 介导的。与 ste12 的缺失不同，S. macrospora 中 sip2 的缺失仅导致子囊孢子萌发略有下降，没有其他明显的形态表型。与 Δste12 单敲除菌株相比，Δsip2/ste12 双敲除菌株中的子囊孢子萌发显著增加。我们的数据为新型真菌蛋白 SIP2 在子囊孢子萌发中的调节作用提供了证据。
