THE DISRUPTION OF ND10 DURING HERPES-SIMPLEX VIRUS-INFECTION CORRELATES WITH THE VMW11O-DEPENDENT AND PROTEASOME-DEPENDENT LOSS OF SEVERAL PML ISOFORMS

The small nuclear structures known as ND10 or PML nuclear bodies have been implicated in a variety of cellular processes including response to stress and interferons, oncogenesis, and viral infection, but littl e is known about their biochemical properties. Recently, a ubiquitin-s pecific protease enzyme (named HAUSP) and a ubiquitin-homology family protein (PIC1) have been found associated with ND10. HAUSP binds stron gly to Vmw110, a herpesvirus regulatory protein which has the ability to disrupt ND10, while PIC1 was identified as a protein which interact s with PML, the prototype ND10 protein. We have investigated the role of ubiquitin-related pathways in the mechanism of ND10 disruption by V mw110 and the effect of virus infection on PML stability. The results show that the disruption of ND10 during virus infection correlates wit h the loss of several PML isoforms and this process is dependent on ac tive proteasomes. The PML isoforms that are most sensitive to virus in fection correspond closely to those which have recently been identifie d as being covalently conjugated to PIC1. In addition, a large number of PIC1-protein conjugates can be detected following transfection of a PIC1 expression plasmid, and many of these are also eliminated in a V mw110-dependent manner during virus infection. These observations prov ide a biochemical mechanism to explain the observed effects of Vmw110 on ND10 and suggest a simple yet powerful mechanism by which Vmw110 mi ght function during virus infection.