NUB1-mediated targeting of the ubiquitin precursor UbC1 for its C-terminal hydrolysis.
NUB1-mediated targeting of the ubiquitin precursor UbC1 for its C-terminal hydrolysis.
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DOI：
10.1111/j.1432-1033.2004.03999.x
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发表时间：
2004-03
期刊：
影响因子：
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通讯作者：
Tomoaki Tanaka;E. Yeh;T. Kamitani
中科院分区：
文献类型：
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作者：
Tomoaki Tanaka;E. Yeh;T. Kamitani
NEDD8是一种泛素样蛋白，通过与靶蛋白的结合来控制重要的生物事件。此前，我们发现了NEDD8结合系统的负调控因子NEDD8终极阻断器-1(NUB1)，它将NEDD8及其结合物招募到蛋白酶体上进行降解。最近，我们以NUB1为诱饵进行酵母双杂交筛选，分离到一个泛素前体Ubc1，它由一个泛素单位的9个串联重复序列通过α-肽键组成。有趣的是，NUB1通过其UBA结构域与UbC1相互作用。进一步的研究表明，UBA结构域与α-肽键连接的多泛素相互作用，而不与异肽键连接的多泛素相互作用，表明NUB1的UBA结构域是线性泛素前体的特异性受体。一项功能研究表明，一种与NUB1免疫共沉淀的未知蛋白是UbC1的泛素C末端水解酶。因此，NUB1似乎与未知的泛素C末端水解酶形成了一个蛋白质复合体，并将UbC1招募到这个复合体中。这可能允许泛素C-末端水解酶水解UbC1，以产生泛素单体。Northern印迹分析表明，NUB1和UbC1mRNAs在精巢中均有丰富的表达。原位杂交结果显示，两种mRNAs均在睾丸曲细精管中强表达。这些结果可能表明，由NUB1介导的UbC1水解酶参与了生精小管的细胞功能，如精子发生。
NEDD8 is a ubiquitin-like protein that controls vital biological events through its conjugation to target proteins. Previously, we identified a negative regulator of the NEDD8 conjugation system, NEDD8 ultimate buster-1 (NUB1), that recruits NEDD8 and its conjugates to the proteasome for degradation. Recently, we performed yeast two-hybrid screening with NUB1 as bait and isolated a ubiquitin precursor UbC1 that is composed of nine tandem repeats of a ubiquitin unit through alpha-peptide bonds. Interestingly, NUB1 interacted with UbC1 through its UBA domain. Further study revealed that the UBA domain interacted with alpha-peptide bond-linked polyubiquitin, but not with isopeptide bond-linked polyubiquitin, indicating that the UBA domain of NUB1 is a specific acceptor for the linear ubiquitin precursor. A functional study revealed that an unidentified protein that was immunoprecipitated with NUB1 served as a ubiquitin C-terminal hydrolase for UbC1. Thus, NUB1 seems to form a protein complex with the unidentified ubiquitin C-terminal hydrolase and recruit UbC1 to this complex. This might allow the ubiquitin C-terminal hydrolase to hydrolyze UbC1, in order to generate ubiquitin monomers. Northern blot analysis showed that the mRNAs of both NUB1 and UbC1 were enriched in the testis. Furthermore, in situ hybridization showed that both mRNAs were strongly expressed in seminiferous tubules of the testis. These results may imply that the UbC1 hydrolysis mediated by NUB1 is involved in cellular functions in the seminiferous tubules such as spermatogenesis.