6k5r
From Proteopedia
Complex of SUMO2 with Phosphorylated viral SIM IE2
Structural highlights
Function[SUMO3_HUMAN] Ubiquitin-like protein which can be covalently attached to target lysines either as a monomer or as a lysine-linked polymer. Does not seem to be involved in protein degradation and may function as an antagonist of ubiquitin in the degradation process. Plays a role in a number of cellular processes such as nuclear transport, DNA replication and repair, mitosis and signal transduction. Covalent attachment to its substrates requires prior activation by the E1 complex SAE1-SAE2 and linkage to the E2 enzyme UBE2I, and can be promoted by an E3 ligase such as PIAS1-4, RANBP2 or CBX4.[1] [2] [VIE2_HCMVA] Stimulates viral early and late gene expression and thus play a crucial role in the regulation of productive infection. In addition, activates quiescent cells to reenter the cell cycle and upregulates several E2F-responsive genes, which are responsible for pushing the cell into S phase. In S-phase, inhibits cellular DNA synthesis and blocks further cell cycle progression.[3] [4] Publication Abstract from PubMedMany viral factors manipulate the host post-translational modification (PTM) machinery for efficient viral replication. In particular, phosphorylation and SUMOylation can distinctly regulate the activity of the human cytomegalovirus (HCMV) transactivator immediate early 2 (IE2). However, the molecular mechanism of this process is unknown. Using various structural, biochemical, and cell-based approaches, here we uncovered that IE2 exploits a cross-talk between phosphorylation and SUMOylation. A scan for small ubiquitin-like modifier (SUMO)-interacting motifs (SIMs) revealed two SIMs in IE2, and a real-time SUMOylation assay indicated that the N-terminal SIM (IE2-SIM1) enhances IE2 SUMOylation up to 4-fold. Kinetic analysis and structural studies disclosed that IE2 is a SUMO cis-E3 ligase. We also found that two putative casein kinase 2 (CK2) sites adjacent to IE2-SIM1 are phosphorylated in vitro and in cells. The phosphorylation drastically increased IE2-SUMO affinity, IE2 SUMOylation, and cis-E3 activity of IE2. Additional salt bridges between the phosphoserines and SUMO accounted for the increased IE2-SUMO affinity. Phosphorylation also enhanced the SUMO-dependent transactivation activity and auto-repression activity of IE2. Together, our findings highlight a novel mechanism whereby SUMOylation and phosphorylation of the viral cis-E3 ligase and transactivator protein IE2 work in tandem to enable transcriptional regulation of viral gene. Casein kinase-2-mediated phosphorylation increases the SUMO-dependent activity of the cytomegalovirus transactivator IE2.,Tripathi V, Chatterjee KS, Das R J Biol Chem. 2019 Oct 4;294(40):14546-14561. doi: 10.1074/jbc.RA119.009601. Epub , 2019 Aug 1. PMID:31371453[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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