Enzymes catalyzing ubiquitination and proteolytic processing of the p105 precursor of nuclear factor κB1
Enzymes catalyzing ubiquitination and proteolytic processing of the p105 precursor of nuclear factor κB1
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DOI：
10.1074/jbc.273.15.8820
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发表时间：
1998-04-10
影响因子：
4.8
通讯作者：
Goldberg, AL
中科院分区：
文献类型：
--
作者：
Coux, O;Goldberg, AL
核因子 kappa B1 (NF-kappa B) 是一种异二聚体复合物，可调节许多参与免疫和炎症反应的基因的转录。其 50 kDa 亚基 (p50) 由 105 kDa 前体 (p105) 的泛素蛋白酶体途径生成。我们在 HeLa 细胞提取物中重建了这种蛋白水解过程，并纯化了相关酶。 p105的泛素化需要E1和两种类型的E2中的任一种：E2-25K(其中p105是第一个被证实的底物)或UBCH5(UBC4)家族的成员。它还需要一个新的50 kDa的E3，我们称之为E3 kappa B。这组酶与其他人报道的催化网织红细胞中p105泛素化的E2和E3不同。此处纯化的泛素化酶与 26S 蛋白酶体一起形成 p50。因此，26S 蛋白酶体提供 p105 加工所需的所有蛋白水解活性。有趣的是，在重建的系统中，正如在细胞中观察到的那样，p105（p97）的 C 端截短形式比正常 p105 更有效地加工成 p50，即使这两个物种的泛素化程度相似。因此，涉及 p105 C 末端区域的一些额外机制影响泛素化前体的蛋白水解加工。
Nuclear factor kappa B1 (NF-kappa B) is a heterodimeric complex that regulates transcription of many genes involved in immune and inflammatory responses. Its 50-kDa subunit (p50) is generated by the ubiquitin-proteasome pathway from a 105-kDa precursor (p105). We have reconstituted this proteolytic process in HeLa cell extracts and purified the responsible enzymes. Ubiquitination of p105 requires El, and either of two types of E2s, E2-25K (for which p105 is the first proven substrate) or a member of the UBCH5 (UBC4) family. It also requires a new E3 of 50 kDa, which we call E3 kappa B. This set of enzymes differs from the E2s and E3 reported by others to catalyze p105 ubiquitination in reticulocytes. The ubiquitinating enzymes purified here, together with 26S proteasomes, allowed formation of p50. Thus, the 26S proteasome provides all the proteolytic activities necessary for p105 processing. Interestingly, in the reconstituted system, as observed in cells, the C-terminally truncated form of p105, p97, was processed into p50 more efficiently than normal p105, even when both species were ubiquitinated to a similar extent. Therefore, some additional mechanism involving the C-terminal region of p105 influences the proteolytic processing of the ubiquitinated precursor.