Klassen Roland, Jablonowski Daniel, Stark Michael J R, Schaffrath Raffael, Meinhardt Friedhelm
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany.
FEMS Yeast Res. 2006 May;6(3):404-13. doi: 10.1111/j.1567-1364.2005.00006.x.
Killer-toxin complexes produced by Kluyveromyces lactis and Pichia acaciae inhibit cell proliferation of Saccharomyces cerevisiae. Analysis of their actions in haploid MATalpha cells revealed that introduction of the opposite mating-type locus (MATa) significantly suppressed antizymosis. Together with resistance expressed by MATa/MATalpha diploids, the reciprocal action of MATa or MATalpha in haploids of opposite mating types suggests that these killer toxins may be subject to MAT locus control. Congruently, derepressing the silent mating-type loci, HMR and HML, by removing individual components of the histone deacetylase complex Sir1-4, either by transposon-tagging or by chemically inactivating the histone deacetylase catalytic subunit Sir2, yields toxin resistance. Consistent with MAT control of toxin action, killer-toxin-insensitive S. cerevisiae mutants (kti) become mating-compromised despite resisting the toxins' cell-cycle effects. Mating inhibition largely depends on the time point of toxin application to the mating mixtures and is less pronounced in Elongator mutants, whose resistance to the toxins' cell-cycle effects is the result of toxin-target process deficiencies. In striking contrast, non-Elongator mutants defective in early-response events such as toxin import/activation hardly recover from toxin-induced mating inhibition. This study reveals a novel effect of yeast killer toxins on mating and sexual reproduction that is independent of their impact on cellular proliferation and cell-cycle progression.
乳酸克鲁维酵母和金合欢毕赤酵母产生的杀伤毒素复合物可抑制酿酒酵母的细胞增殖。对其在单倍体MATα细胞中的作用分析表明，引入相反的交配型基因座（MATa）可显著抑制抗发酵作用。结合MATa/MATα二倍体所表现出的抗性，MATa或MATα在相反交配型单倍体中的相互作用表明，这些杀伤毒素可能受交配型基因座控制。同样，通过转座子标签法或化学方法使组蛋白脱乙酰酶催化亚基Sir2失活，去除组蛋白脱乙酰酶复合物Sir1-4的各个组分，从而解除沉默交配型基因座HMR和HML的抑制，可产生毒素抗性。与毒素作用受MAT控制一致，对杀伤毒素不敏感的酿酒酵母突变体（kti）尽管能抵抗毒素对细胞周期的影响，但交配能力受损。交配抑制很大程度上取决于向交配混合物中施加毒素的时间点，在延伸因子突变体中不太明显，其对毒素细胞周期效应的抗性是毒素靶向过程缺陷的结果。与之形成鲜明对比的是，早期反应事件（如毒素导入/激活）存在缺陷的非延伸因子突变体很难从毒素诱导的交配抑制中恢复。这项研究揭示了酵母杀伤毒素对交配和有性生殖的一种新作用，这种作用独立于它们对细胞增殖和细胞周期进程的影响。
