Shope fibroma virus (SFV) N1R gene encodes a RING finger protein that localizes to virus factories within the cytoplasm of infected cells. Altered proteins, with deletions and site-specific mutations, were transiently expressed in vaccinia virus-infected cells to discern regions of the protein that are required for localization. We have determined that at least part of the RING finger region is necessary for localization but that the RING motif alone is not sufficient. A chimeric protein, however, in which the RING finger region of the herpes simplex virus-1 ICPO protein replaces the SFV N1R RING motif does localize to virus factories. A region of five highly conserved amino acids at the amino terminus of SFV N1R is also critical for localization. We report that the SFV N1R protein binds double- and single- stranded DNA, suggesting a mechanism for localization, and that overexpression of this protein in vaccinia virus-infected cells reduces apoptosis-associated fragmentation of nuclear DNA.
Bibliographical noteFunding Information:
This research was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) Operating Grant (C.U.), NSERC and Heart and Stroke Foundation of BC and Yukon Operating Grants (R.B.), and National Institutes of Health Grant R29A132139 (L.S.). We thank Yasanna Quin and Chris King for excellent technical assistance.