Interactions among four proteins encoded by the human cytomegalovirus UL112-113 region regulate their intranuclear targeting and the recruitment of UL44 to prereplication foci.
Four phosphoproteins, of 34, 43, 50, and 84 kDa, with common amino termini are synthesized via alternative splicing from the UL112-113 region of the human cytomegalovirus genome. Although genetic studies provided evidence that both the UL112 and UL113 loci in the viral genome are required for efficient viral replication, whether the four proteins play specific roles or cooperate in replication is not understood. Here we present evidence, using in vitro and in vivo coimmunoprecipitation assays, that the four UL112-113 proteins both self-interact and interact with each other. A mapping study of the 84-kDa protein showed that the N-terminal region encompassing amino acids 1 to 125, which is shared in all UL112-113 proteins and highly conserved among betaherpesviruses, is required for both self-interaction and nuclear localization as foci. Further localization studies revealed that, unlike the 43-, 50-, and 84-kDa proteins, which were distributed as nuclear punctate forms, the 34-kDa form was located predominantly in the cytoplasm. However, when all four proteins were coexpressed simultaneously, all of the UL112-113 proteins were efficiently localized to the promyelocytic leukemia oncogenic domains. We also found that the ability of the UL112-113 proteins to relocate UL44 (the viral polymerase processivity factor) to prereplication foci relied on self-interaction and reached maximal levels when the four proteins were coexpressed. Therefore, our data suggest that interactions occurring among UL112-113 proteins via their shared N-terminal regions are important to both their intranuclear targeting and the recruitment of UL44 to subnuclear sites for viral replication.
Park
Mi-Young
MY
Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, 300 Chunchundong Jangangu, Suwon, Kyonggido 440-746, Korea.
Kim
Young-Eui
YE
Seo
Myong-Rang
MR
Lee
Jae-Rin
JR
Lee
Chan Hee
CH
Ahn
Jin-Hyun
JH
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D003587:Cytomegalovirus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D004268:DNA-Binding Proteins; C072217:ICP36 protein, Cytomegalovirus; D010750:Phosphoproteins; D014764:Viral Proteins