Murine cytomegalovirus M72 promotes acute virus replication in vivo and is a substrate of the TRiC/CCT complex

Betaherpesvirus dUTPase homologs are core herpesvirus proteins, but little is known about their role during infection. Human cytomegalovirus (HCMV) UL72 and murine cytomegalovirus (MCMV) M72 have been designated dUTPase homologs, and previous studies indicate UL72 is dispensable for replication and enzymatically inactive. Here, we report the initial characterization of MCMV M72. M72 does not possess dUTPase activity, and is expressed as a leaky-late gene product with multiple protein isoforms. Importantly, M72 augments MCMV replication in vitro and during the early stage of acute infection in vivo. We identify and confirm interaction of M72 with the eukaryotic chaperonin tailless complex protein -1 (TCP-1) ring complex (TRiC) or chaperonin containing tailless complex polypeptide 1 (CCT). Accumulating biochemical evidence indicates M72 forms homo-oligomers and is a substrate of TRiC/CCT. Taken together, we provide the first evidence of M72's contribution to viral pathogenesis, and identify a novel interaction with the TRiC/CCT complex.