HSV-2 R1, the R1 subunit of herpes simplex virus (HSV) ribonucleotide reductase, protects cells against apoptosis. Here, we report the presence in HSV-2 R1 of a stretch exhibiting similarity to the α-crystallin domain of the small heat shock proteins, a domain known to be important for oligomerization and cytoprotective activities of these proteins. Also, the HSV-2 R1 protein, which forms multimeric structures in the absence of nucleotide, displayed chaperone ability as good as Hsp27 in a thermal denaturation assay using citrate synthase. In contrast, mammalian R1, which does not contain an α-crystallin domain, has neither chaperone nor anti-apoptotic activity. Thus, we propose that the chaperone activity of HSV-2 R1 could play an important role in viral pathogenesis.
