Herpes simplex virus type 1 C-terminal variants of the origin binding protein (OBP), OBPC-1 and OBPC-2, cooperatively regulate viral DNA levels in vitro, and OBPC-2 affects mortality in mice.
Two in-frame, C-terminal isoforms of the herpes simplex virus type 1 (HSV-1) origin binding protein (OBP), OBPC-1 and OBPC-2, and a unique C-terminal transcript, UL8.5, are specified by HSV-1 DNA. As the first isoform identified, OBPC-1 was initially assumed to be the product of the UL8.5 transcript. Recent evidence has demonstrated, however, that OBPC-1 is a cathepsin B-mediated cleavage product of OBP, suggesting that OBPC-2 is the product of the UL8.5 transcript. Because both OBPC-1 and -2 contain the majority of the OBP DNA binding domain, we hypothesized that both may be involved in regulating origin-dependent, OBP-mediated viral DNA replication. In this paper, we demonstrate that OBPC-2 is, indeed, the product of the UL8.5 transcript. The translational start site of OBPC-2 was mapped, and a virus (M571A) that does not express this protein efficiently was constructed. Using M571A, we have shown that OBPC-2 is able to bind origin DNA, even though it lacks seven N-terminal amino acid residues of the previously mapped OBP DNA binding domain, resulting in a revision of the limits of the OBP DNA binding domain. Consistent with their proposed roles in regulating viral DNA replication, OBPC-1 and -2 act together to down-regulate viral DNA replication in vitro. During functional studies in vivo, OBPC-2 was identified as a factor that increases mortality in the mouse ocular model of HSV-1 infection.
Link
Malen A
MA
Department of Medicine, Harvard Medical School at Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
Schaffer
Priscilla A
PA
D000818:Animals; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis; D006561:Herpes Simplex / Q000821:virology*; D018259:Herpesvirus 1, Human / Q000235:genetics / Q000502:physiology*; D051379:Mice; D009154:Mutation; D051738:Origin Recognition Complex / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018741:Replication Origin; D014158:Transcription, Genetic; D017735:Virus Latency / Q000235:genetics; D014779:Virus Replication / Q000235:genetics*
D004279:DNA, Viral; D051738:Origin Recognition Complex; D020033:Protein Isoforms