Substrate Targeting and Control of DNA Replication by the CUL4/DDB1 Ubiquitin Ligase Public Deposited

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  • March 20, 2019
Creator
  • McCall, Chad
    • Affiliation: School of Medicine, Department of Biochemistry and Biophysics
Abstract
  • Ubiqutin-mediated proteolysis is an essential pathway in the cell, by which specific proteins are targeted for degradation at specific times. The small protein ubiquitin is conjugated onto targets for proteolysis by a series of three enzymatic reactions, catalyzed by an E1 ubiquitin activating enzyme, an E2 ubiquitin conjugating enzyme, and one of hundreds of E3 ubiquitin ligases. E3 ubiquitin ligases provide specificity for the reaction by interacting with specific substrates and an E2. The cullin family of ligases is particularly important because their modular domain structure allows for many ligases to be formed from a minimum of components. In this study, I describe research into the substrate-targeting mechanism of Cullin 4A. First, I identified by mass spectrometry a substrate receptor family containing a specific motif within WD-40 repeats that interacts with a common Cullin 4A adaptor, DDB1. In collaboration with others in my laboratory, we determined that more than 90 potential receptors contain this "DWD" motif. I then characterized one of these receptors, VprBP, which is required for normal cellular proliferation. VprBP silencing leads to a defect in DNA replication, whereby replication stress leads to an upregulation of cryptic origins of replication but an overall decrease in nucleotide incorporation. It also interacts with the HIV-1 accessory protein Vpr, and bridges the Vpr ubiquitination substrate UNG2 to the CUL4A ligase.
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  • In Copyright
Advisor
  • Patterson, Cam
  • Marzluff, William
  • Xiong, Yue
  • Chaney, Stephen
  • Cook, Jean
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2007
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