A SnapShot of Ubiquitin Chain Elongation LYSINE 48-TETRA-UBIQUITIN SLOWS DOWN UBIQUITINATION

作者：Kovacev, Jordan; Wu, Kenneth; Spratt, Donald E.; Chong, Robert A.; Lee, Chan; Nayak, Jaladhi; Shaw, Gary S.; Pan, Zhen-Qiang^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2014, 289(10): 7068-7081.

DOI：10.1074/jbc.M113.530576

• Catenin
• E3 Ubiquitin Ligase
• Enzymes
• Post Translational Modification
• Protein Degradation
• Ubiquitination
• Cdc34
• E2 Conjugating Enzyme
• SCF
• UbcH5c

Background: Polyubiquitin chains are signaling polypeptides altering the fate of substrates. Results: A Lys-48-ubiquitin chain of a length greater than four, but not its Lys-63 linkage counterparts, slowed the rate of additional ubiquitin conjugation. Conclusion: The ubiquitin chain length and linkage may impact kinetic rates of chain elongation. Significance: Our findings suggest a self-restraining mechanism that limits Lys-48-polyubiquitination.
We have explored the mechanisms of polyubiquitin chain assembly with reconstituted ubiquitination of IB and -catenin by the Skp1-cullin 1-TrCP F-box protein (SCFTrCP) E3 ubiquitin (Ub) ligase complex. Competition experiments revealed that SCFTrCP formed a complex with IB and that the Nedd8 modified E3-substrate platform engaged in dynamic interactions with the Cdc34 E2 Ub conjugating enzyme for chain elongation. Using elongation intermediates containing -catenin linked with Ub chains of defined length, it was observed that a Lys-48-Ub chain of a length greater than four, but not its Lys-63 linkage counterparts, slowed the rate of additional Ub conjugation. Thus, the Ub chain length and linkage impact kinetic rates of chain elongation. Given that Lys-48-tetra-Ub is packed into compact conformations due to extensive intrachain interactions between Ub subunits, this topology may limit the accessibility of SCFTrCP/Cdc34 to the distal Ub Lys-48 and result in slowed elongation.

• 出版日期2014-3-7
• 单位徐州医科大学