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Nat Cell Biol January 29, 2012; 14 (2): 168-76.
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APC/C-mediated multiple monoubiquitylation provides an alternative degradation signal for cyclin B1.

Dimova NV , Hathaway NA , Lee BH , Kirkpatrick DS , Berkowitz ML , Gygi SP , Finley D , King RW .

The anaphase-promoting complex or cyclosome (APC/C) initiates mitotic exit by ubiquitylating cell-cycle regulators such as cyclin B1 and securin. Lys 48-linked ubiquitin chains represent the canonical signal targeting proteins for degradation by the proteasome, but they are not required for the degradation of cyclin B1. Lys 11-linked ubiquitin chains have been implicated in degradation of APC/C substrates, but the Lys 11-chain-forming E2 UBE2S is not essential for mitotic exit, raising questions about the nature of the ubiquitin signal that targets APC/C substrates for degradation. Here we demonstrate that multiple monoubiquitylation of cyclin B1, catalysed by UBCH10 or UBC4/5, is sufficient to target cyclin B1 for destruction by the proteasome. When the number of ubiquitylatable lysines in cyclin B1 is restricted, Lys 11-linked ubiquitin polymers elaborated by UBE2S become increasingly important. We therefore explain how a substrate that contains multiple ubiquitin acceptor sites confers flexibility in the requirement for particular E2 enzymes in modulating the rate of ubiquitin-dependent proteolysis.

PubMed ID: 22286100
PMC ID: PMC3278798
Article link: Nat Cell Biol
Grant support: [+]

Species referenced: Xenopus
Genes referenced: ccnb1 cdk1 psmd4 rrad ube2d1 ube2s usp14

Article Images: [+] show captions
References [+] :
Baboshina, Novel multiubiquitin chain linkages catalyzed by the conjugating enzymes E2EPF and RAD6 are recognized by 26 S proteasome subunit 5. 1996, Pubmed