Cuchet-Lourenco D, Vanni E, Glass M, Orr A, Everett RD

Herpes simplex virus type 1 (HSV-1) immediate-early protein ICP0 localizes to cellular structures known as PML nuclear bodies or ND10 and disrupts their integrity by inducing the degradation of PML. There are six PML isoforms with different C-terminal regions in ND10, of which PML isoform I (PML.I) is the most ...

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abundant. Depletion of all PML isoforms increases the plaque formation efficiency of ICP0-null mutant HSV-1, and reconstitution of expression of PML.I and PML.II partially reverses this improved replication. ICP0 also induces widespread degradation of SUMO-conjugated proteins during HSV-1 infection, and this activity is linked to its ability to counteract cellular intrinsic antiviral resistance. All PML isoforms are highly SUMO-modified, and all such modified forms are sensitive to ICP0-mediated degradation. However, in contrast to the situation with the other isoforms, ICP0 also targets PML.I that is not modified by SUMO, and PML in general is degraded more rapidly than the bulk of other SUMO-modified proteins. We report that ICP0 interacts with PML.I in both yeast two-hybrid and co-immunoprecipitation assays. This interaction is dependent on PML.I isoform-specific sequences and the N-terminal half of ICP0, and is required for SUMO-modification independent degradation of PML.I by ICP0. Degradation of the other PML isoforms by ICP0 was less efficient in cells specifically depleted of PML.I. Therefore, ICP0 has two distinct mechanisms of targeting PML, one dependent on SUMO modification, and the other via SUMO-independent interaction with PML.I. We conclude that the ICP0-PML.I interaction reflects a countermeasure to PML-related antiviral restriction.

Date: Aug. 08, 2012

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