Raju Kalidindi K, Natarajan Sumathi, Kumar N Sunil, Kumar D Anil, N M Raghavendra
Department of Biotechnology, GRIET, Hyderabad 500090, Telangana, India
Department of Biochemistry, Osmania University, Hyderabad 500007, Telangana, India.
FEMS Yeast Res. 2015 Mar;15(2). doi: 10.1093/femsyr/fou006.
Strains of Saccharomyces cerevisiae lacking factors involved in 5' to 3' mRNA decay pathway (DCP1, DCP2, DHH1, PAT1, LSM1 and LSM4) exhibit caspase-dependent apoptosis and accelerated chronological aging. In the present study, yeast strains lacking mRNA decapping activation factors (DCP2 and LSM1), cytoplasmic exosome function (SKI2) or cytoplasmic deadenylases (double deletion of CCR4 and PAN2) showed typical markers of eukaryotic apoptosis such as increased cellular reactive oxygen species levels, externalization of phosphatidyl serine, chromatin fragmentation, enhanced caspase gene (YCA1) expression and protein activity in mid-log phase cultures. The transcript levels of negative regulators of mRNA decapping (eIF4E and Pab1) were considerably elevated in strains defective in cytoplasmic deadenylation and reduced in strains lacking cytoplasmic 3' to 5' exosome function or decapping activators. Among the yeast strains studied, lsm1Δ and ccr4Δpan2Δ mutants displayed strongest apoptotic phenotype followed by mutants lacking DCP2 or SKI2. Among yeast strains exhibiting deadenylation defects, slight apoptotic phenotype was observed in ccr4Δ mutants and cell death markers imperceptible in pan2Δ mutants.
缺乏参与5'至3'mRNA降解途径的因子（DCP1、DCP2、DHH1、PAT1、LSM1和LSM4）的酿酒酵母菌株表现出半胱天冬酶依赖性凋亡和加速的时序衰老。在本研究中，缺乏mRNA脱帽激活因子（DCP2和LSM1）、细胞质外泌体功能（SKI2）或细胞质去腺苷酸化酶（CCR4和PAN2双缺失）的酵母菌株在对数中期培养物中表现出真核细胞凋亡的典型标志物，如细胞活性氧水平升高、磷脂酰丝氨酸外化、染色质片段化、半胱天冬酶基因（YCA1）表达增强和蛋白质活性增强。在细胞质去腺苷酸化缺陷的菌株中，mRNA脱帽负调节因子（eIF4E和Pab1）的转录水平显著升高，而在缺乏细胞质3'至5'外泌体功能或脱帽激活因子的菌株中则降低。在所研究的酵母菌株中，lsm1Δ和ccr4Δpan2Δ突变体表现出最强的凋亡表型，其次是缺乏DCP2或SKI2的突变体。在表现出去腺苷酸化缺陷的酵母菌株中，在ccr4Δ突变体中观察到轻微的凋亡表型，而在pan2Δ突变体中未观察到细胞死亡标志物。
