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首页> 外文期刊>Molecular and Cellular Biology >Two Ubiquitin-Conjugating Enzymes, UbcP1/Ubc4 and UbcP4/Ubc11, Have Distinct Functions for Ubiquitination of Mitotic Cyclin
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Two Ubiquitin-Conjugating Enzymes, UbcP1/Ubc4 and UbcP4/Ubc11, Have Distinct Functions for Ubiquitination of Mitotic Cyclin

机译：两种泛素结合酶，UbcP1 / Ubc4和UbcP4 / Ubc11，对有丝分裂细胞周期素的泛素化具有不同的功能。

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Cell cycle events are regulated by sequential activation and inactivation of Cdk kinases. Mitotic exit is accomplished by the inactivation of mitotic Cdk kinase, which is mainly achieved by degradation of cyclins. The ubiquitin-proteasome system is involved in this process, requiring APC/C (anaphase-promoting complex/cyclosome) as a ubiquitin ligase. In Xenopus and clam oocytes, the ubiquitin-conjugating enzymes that function with APC/C have been identified as two proteins, UBC4 and UBCx/E2-C. Previously we reported that the fission yeast ubiquitin-conjugating enzyme UbcP4/Ubc11, a homologue of UBCx/E2-C, is required for mitotic transition. Here we show that the other fission yeast ubiquitin-conjugating enzyme, UbcP1/Ubc4, which is homologous to UBC4, is also required for mitotic transition in the same manner as UbcP4/Ubc11. Both ubiquitin-conjugating enzymes are essential for cell division and directly required for the degradation of mitotic cyclin Cdc13. They function nonredundantly in the ubiquitination of CDC13 because a defect in ubcP1/ubc4+ cannot be suppressed by high expression of UbcP4/Ubc11 and a defect in ubcP4/ubc11+ cannot be suppressed by high expression of UbcP1/Ubc4. In vivo analysis of the ubiquitinated state of Cdc13 shows that the ubiquitin chains on Cdc13 were short in ubcP1/ubc4 mutant cells while ubiquitinated Cdc13 was totally reduced in ubcP4/ubc11 mutant cells. Taken together, these results indicate that the two ubiquitin-conjugating enzymes play distinct and essential roles in the degradation of mitotic cyclin Cdc13, with the UbcP4/Ubc11-pathway initiating ubiquitination of Cdc13 and the UbcP1/Ubc4-pathway elongating the short ubiquitin chains on Cdc13.
机译：细胞周期事件是由Cdk激酶的顺序激活和失活调节的。有丝分裂的退出是通过使有丝分裂的Cdk激酶失活来实现的，这主要是通过细胞周期蛋白的降解来实现的。泛素-蛋白酶体系统参与此过程，需要APC / C（后期促进复合物/环体）作为泛素连接酶。在非洲爪蟾卵和蛤卵母细胞中，与APC / C起作用的泛素结合酶已被鉴定为两种蛋白，UBC4和UBCx / E2-C。先前我们报道裂变酵母泛素结合酶UbcP4 / Ubc11（UBCx / E2-C的同源物）是有丝分裂过渡所必需的。在这里，我们显示了与UBC4同源的其他裂变酵母泛素结合酶UbcP1 / Ubc4也需要与UbcP4 / Ubc11相同的有丝分裂过渡。两种泛素结合酶对于细胞分裂都是必不可少的，是有丝分裂细胞周期蛋白Cdc13降解的直接需要。它们在CDC13的泛素化中具有非冗余功能，因为 ubcP1 / ubc4 + 中的缺陷不能通过UbcP4 / Ubc11的高表达和 ubcP4 / ubc11中的缺陷来抑制 + 不能通过高表达UbcP1 / Ubc4来抑制。 Cdc13泛素化状态的体内分析表明， ubcP1 / ubc4 突变细胞中Cdc13的泛素链短，而 ubcP4 / ubc11 突变细胞中Cdc13的泛素链却被完全还原。 。综上所述，这些结果表明这两种泛素结合酶在有丝分裂细胞周期蛋白Cdc13的降解中起着独特而重要的作用，其中UbcP4 / Ubc11途径使Cdc13泛素化，而UbcP1 / Ubc4途径使短的泛素链延长。 Cdc13。

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