Dissecting beta-ring assembly pathway of the mammalian 20S proteasome

作者：Hirano Yuko; Kaneko Takeumi; Okamoto Kenta; Bai Minghui; Yashiroda Hideki; Furuyama Kaori; Kato Koichi; Tanaka Keiji; Murata Shigeo^*

来源：The EMBO Journal, 2008, 27(16): 2204-2213.

DOI：10.1038/emboj.2008.148

• assembly
• chaperone
• propeptide
• proteasome
• ubiquitin

The 20S proteasome is the catalytic core of the 26S proteasome. It comprises four stacked rings of seven subunits each, alpha(1-7)beta(1-7)beta(1-7)alpha(1-7). Recent studies indicated that proteasome-specific chaperones and beta-subunit appendages assist in the formation of alpha-rings and dimerization of half-proteasomes, but the process involved in the assembly of beta-rings is poorly understood. Here, we clarify the mechanism of beta- ring formation on alpha-rings by characterizing assembly intermediates accumulated in cells depleted of each beta-subunit. Starting from beta 2, incorporation of beta-subunits occurs in an orderly manner dependent on the propeptides of beta 2 and beta 5, and the C-terminal tail of beta 2. Unexpectedly, hUmp1, a chaperone functioning at the final assembly step, is incorporated as early as beta 2 and is required for the structural integrity of early assembly intermediates. We propose a model in which beta-ring formation is assisted by both intramolecular and extrinsic chaperones, whose roles are partially different between yeast and mammals.

• 出版日期2008-8-20
• 单位河北医科大学