Mcl-1是Bcl-2家族蛋白的成员;其降解是启动细胞凋亡所必需的。机制,然而,尚不清楚。以前,据报道,Mcl-1通过泛素化介导的途径降解,并且PEST结构域是负责促进这种降解的基序。我们发现有证据表明这可能不是真的。我们产生了几个Mcl-1缺失突变体,并检查了它们对蛋白质稳定性的影响。PEST结构域的缺失不能阻止细胞凋亡期间Mcl-1的降解。BH1域,但不是PEST,BH3或BH2结构域,表现出短暂的半衰期。BH1结构域C末端的名为“F3”(VTLISFG)的肽似乎对于Mcl-1的快速周转至关重要。从GFP-Mcl-1-ΔPEST中缺失F3延缓了该突变体的降解。F3似乎是降解基序的最小功能序列,因为单个残基的缺失足以消除其短暂的半衰期。F3与p32融合导致p32在紫外线诱导的细胞凋亡过程中降解,而野生型p32未受影响。一起来看,这些发现表明F3(VTLISFG),而不是PEST,是负责细胞凋亡过程中Mcl-1降解的主要基序。
Mcl-1 is a member of the Bcl-2 family protein; its degradation is required for the initiation of apoptosis. The mechanism, however, is not yet clearly known. Previously, it was reported that Mcl-1 is degraded through the ubiquitination-mediated pathway and the PEST domain is the motif responsible for promoting this degradation. We found evidence that this may not be true. We generated several Mcl-1 deletion mutants and examined their effects on protein stability. Deletion of the PEST domain did not prevent the degradation of Mcl-1 during apoptosis. The BH1 domain, but not the PEST, BH3 or BH2 domain, exhibited a short half-life. A peptide named \"F3\" (VTLISFG) in the C-terminus of the BH1 domain appears to be critical for the rapid turnover of Mcl-1. Deletion of F3 from GFP-Mcl-1-ΔPEST retarded the degradation of this mutant. F3 appeared to be the minimum functional sequence of the degradation motif, since deletion of a single residue was sufficient to abrogate its short half-life. Fusion of F3 with p32 resulted in the degradation of p32 during UV-induced apoptosis, while wild type p32 was not affected. Taken together, these findings suggest that F3 (VTLISFG), instead of PEST, is the major motif responsible for the degradation of Mcl-1 during apoptosis.