THE GENOME OF MOLLUSCUM CONTAGIOSUM VIRUS - ANALYSIS AND COMPARISON WITH OTHER POXVIRUSES

Analysis of the molluscum contagiosum virus (MCV) genome revealed that it encodes approximately 182 proteins, 105 of which have direct count erparts in orthopoxviruses (OPV). The corresponding OPV proteins compr ise those known to be essential for replication as well as many that a re still uncharacterized, including 2 of less than 60 amino acids that had not been previously noted. The OPV proteins most highly conserved in MCV are involved in transcription; the least conserved include mem brane glycoproteins. Twenty of the MCV proteins with OPV counterparts also have cellular homologs and additional MCV proteins have conserved functional motifs. Of the 77 predicted MCV proteins without OPV count erparts, 10 have similarity to other MCV proteins and/or distant simil arity to proteins of other poxviruses and 16 have cellular homologs in cluding some predicted to antagonize host defenses. Clustering poxviru s proteins by sequence similarity revealed 3 unique MCV gene families and 8 families that are conserved in MCV and OPV. Two unique families contain putative membrane receptors; the third includes 2 proteins, ea ch containing 2 DED apoptosis signal transduction domains. Additional families with conserved patterns of cysteines and putative redox activ e centers were identified. Promoters, transcription termination signal s, and DNA concatemer resolution sequences are highly conserved in MCV and OPV. Phylogenetic analysis suggested that MCV, OPV, and leporipox viruses radiated from a common poxvirus ancestor after the divergence of avipoxviruses. Despite the acquisition of unique genes for host int eractions and changes in GC content, the physical order and regulation of essential ancestral poxvirus genes have been largely conserved in MCV end OPV. (C) 1997 Academic Press.