Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto, Japan.
Faculty of Science and Engineering, Department of Life Science, Setsunan University, Ikeda-Nakamachi, Neyagawa, Osaka, Japan.
PLoS One. 2020 Nov 11;15(11):e0242054. doi: 10.1371/journal.pone.0242054. eCollection 2020.
Tup1-Cyc8 (also known as Tup1-Ssn6) is a general transcriptional corepressor. D-Mannitol (mannitol) and D-sorbitol (sorbitol) are the major polyols in nature. Budding yeast Saccharomyces cerevisiae is unable to assimilate mannitol or sorbitol, but acquires the ability to assimilate mannitol due to a spontaneous mutation in TUP1 or CYC8. In this study, we found that spontaneous mutation of TUP1 or CYC8 also permitted assimilation of sorbitol. Some spontaneous nonsense mutations of CYC8 produced a truncated Cyc8 with a C-terminal polyglutamine. The effects were guanidine hydrochloride-sensitive and were dependent on Hsp104, but were complemented by introduction of CYC8, ruling out involvement of a prion. Assimilation of mannitol and sorbitol conferred by other mutations of TUP1 or CYC8 was guanidine hydrochloride-tolerant. It is physiologically reasonable that S. cerevisiae carries this mechanism to acquire the ability to assimilate major polyols in nature.
Tup1-Cyc8（也称为 Tup1-Ssn6）是一种通用转录核心抑制剂。D-甘露醇（甘露醇）和 D-山梨醇（山梨醇）是自然界中主要的多元醇。出芽酵母酿酒酵母不能同化甘露醇或山梨醇，但由于 TUP1 或 CYC8 的自发突变而获得同化甘露醇的能力。在这项研究中，我们发现 TUP1 或 CYC8 的自发突变也允许山梨醇的同化。CYC8 的一些自发无义突变产生了具有 C 末端多聚谷氨酰胺的截断 Cyc8。该效应对盐酸胍敏感，并且依赖于 Hsp104，但通过引入 CYC8 进行了互补，排除了朊病毒的参与。由 TUP1 或 CYC8 的其他突变赋予的甘露醇和山梨醇的同化作用对盐酸胍具有耐受性。酿酒酵母携带这种机制以获得同化自然界中主要多元醇的能力在生理上是合理的。
