Fehlker Marion, Wendler Petra, Lehmann Andrea, Enenkel Cordula
Institut für Biochemie, Humboldt Universität zu Berlin, Universitätsklinikum Charité, Monbijoustrasse 2, D-10117 Berlin, Germany.
EMBO Rep. 2003 Oct;4(10):959-63. doi: 10.1038/sj.embor.embor938. Epub 2003 Sep 12.
Proteasomes are multisubunit proteases that are responsible for regulated proteolysis. The degradation of the proteasomal maturation factor, named Ump1 in yeast, completes the autocatalytic processing of inactive precursor complexes into the proteolytically active core particle (CP) of the proteasome. We have identified Blm3, a conserved nuclear protein, as a new component of Ump1-associated precursor complexes. A lack of Blm3 resulted in an increased rate of precursor processing and an accelerated turnover of Ump1, which suggests that Blm3 prevents premature activation of proteasomal CPs. On the basis of biochemical fractionation experiments combined with in vivo localization studies, we propose that Blm3 joins nascent CPs inside the nucleus to coordinate late stages of proteasome assembly in yeast.
蛋白酶体是负责调控蛋白质水解的多亚基蛋白酶。蛋白酶体成熟因子（在酵母中称为Ump1）的降解，完成了无活性前体复合物的自催化加工，形成蛋白酶体的蛋白水解活性核心颗粒（CP）。我们鉴定出一种保守的核蛋白Blm3，它是与Ump1相关的前体复合物的新组分。缺乏Blm3会导致前体加工速率增加以及Ump1的周转加快，这表明Blm3可防止蛋白酶体CP过早激活。基于生化分级分离实验结合体内定位研究，我们提出Blm3在细胞核内与新生的CP结合，以协调酵母中蛋白酶体组装的后期阶段。
