Binding of HIV-1 Vpr to the Human Homolog of the Yeast DNA Repair Protein RAD23 (hHR23A) Requires Its XPC Binding (XPCB) as Well as the Ubiquitin Associated 2 (UBA2) Domains [Protein Structure and Folding]

December 8th, 2013 by Jung, J., Byeon, I.-J. L., DeLucia, M., Koharudin, L. M. I., Ahn, J., Gronenborn, A. M.

The human homolog of the yeast DNA repair protein RAD23, hHR23A, was previously found to interact with the HIV-1 accessory protein Vpr. hHR23A is a modular protein containing an N-terminal ubiquitin-like (UBL) domain and two ubiquitin associated domains (UBA1 and UBA2), separated by a xeroderma pigmentosum complementation group C binding (XPCB) domain. All domains are connected by flexible linkers. hHR23A binds ubiquitinated proteins and acts as a shuttling factor to the proteasome. Here, we show that hHR23A utilizes both the UBA2 and XPCB domains to form a stable complex with Vpr, linking Vpr directly to cellular DNA repair pathways, and their probable exploitation by the virus. Detailed structural mapping of the Vpr contacts on hHR23A, by NMR, revealed substantial contact surfaces on the UBA2 and XPCB domains. In addition, Vpr binding disrupts an intra-molecular UBL-UBA2 interaction. We also show that Lys48-linked di-ubiquitin (di-UbK48), when binding to UBA1, does not release the bound Vpr from the hHR23A/Vpr complex. Instead, a ternary hHR23A/Vpr/di-UbK48 complex is formed, indicating that Vpr does not necessarily abolish hHR23A-mediated shuttling to the proteasome.
  • Posted in Journal of Biological Chemistry, Publications
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