Pre-mRNA splicing in vertebrates is molecularly linked to other processes. We previously reported that splicing is required for efficient assembly of intron-encoded box C/D small nucleolar ribonucleoprotein (snoRNP). In the spliceosomal C1 complex, snoRNP proteins efficiently assemble onto snoRNA sequences if they are located about 50 nt upstream of the intron branchpoint. Here, we identify the splicing factor responsible for coupling snoRNP assembly to intron excision. Intron binding protein (IBP) 160, a helicase-like protein previously detected in the spliceosomal C1 complex, binds the pre-mRNA in a sequence-independent manner, contacting nucleotides 33-40 upstream of the intron branch site, regardless of whether a snoRNA is present. Depletion of IBP160 abrogates snoRNP assembly in vitro. IBP160 binding directly to a snoRNA located too close to the intron branch site interferes with snoRNP assembly. Thus, IBP160 is the key factor linking snoRNP biogenesis and perhaps other postsplicing events to pre-mRNA splicing.
Nucleocapsid formation is a primary function of the rubella virus capsid protein, which also promotes viral RNA synthesis via an unknown mechanism. The present study demonstrates that in infected cells, the capsid protein is associated with the nonstructural p150 protein via the short self-interacting N-terminal region of the capsid protein. Mutational analyses indicated that hydrophobic amino acids in this N-terminal region are essential for its N-terminal self-interaction, which is critical for the capsid-p150 association. An analysis based on a subgenomic replicon system demonstrated that the self-interacting N-terminal region of the capsid protein plays a key role in promoting viral gene expression. Analyses using a virus-like particle (VLP) system also showed that the self-interacting N-terminal region of the capsid protein is not essential for VLP production but is critical for VLP infectivity. These results demonstrate that the close cooperative actions of the capsid protein and p150 require the short self-interacting N-terminal region of the capsid protein during the life cycle of the rubella virus. IMPORTANCEThe capsid protein of rubella virus promotes viral RNA replication via an unknown mechanism. This protein interacts with the nonstructural protein p150, but the importance of this interaction is unclear. In this study, we demonstrate that the short N-terminal region of the capsid protein forms a homo-oligomer that is critical for the capsid-p150 interaction. These interactions are required for the viral-gene-expression-promoting activity of the capsid protein, allowing efficient viral growth. These findings provide information about the mechanisms underlying the regulation of rubella virus RNA replication via the cooperative actions of the capsid protein and p150. R ubella virus (RV) is the sole member of the genus Rubivirus in the family Togaviridae. RV is an enveloped, single-stranded, positive-sense RNA virus with a genome of approximately 10 kb. The genome acts as an mRNA and contains three untranslated regions and two open reading frames (ORFs). The ORF at the 5= end encodes two nonstructural proteins (NSPs), p150 and p90, which function in viral RNA replication. The other ORF, at the 3= end, encodes three structural proteins (SPs), capsid, E2, and E1, which are integral components of the virion (1). NSP p150 contains several domains that are conserved among other RNA viruses (2, 3). A putative methyltransferase domain and a protease domain are located at the amino (N) and carboxyl (C) termini, respectively (2, 4, 5). There are also two domains of unknown function, Y and X, between the methyltransferase and protease domains. The putative methyltransferase domain is considered to play a role in capping viral RNA (4). The protease domain cleaves the precursor polyprotein p200 into p150 and p90, and this step is critical in the regulation of viral RNA replication (6-8). NSP p90 has two functional domains, helicase and RNA-dependent RNA polymerase (RdRp) domains, in the N-and C-terminal reg...
ObjectiveMumps-containing vaccine is currently not a component of the national immunization schedule in Lao People’s Democratic Republic (PDR). Mumps itself is not a notifiable disease in the country and the seroprevalence of anti-mumps immunoglobulin G (IgG) in the general population is unknown. In this study, anti-mumps IgG was measured in 2058 blood samples to evaluate population immunity in the country.ResultsThe seroprevalence of anti-mumps IgG showed a gradual increase with increasing age, starting at 10.6% (95% CI 7.4–13.7) in participants aged 1–2 years, and almost plateaued at about 75% in individuals older than 11–12 years, though it still tended toward a small increase up to 89.6% (95% CI 86.6–92.6) in participants aged 40 years or older. Compared with the results of previous studies, this increase with increasing age is less marked and the plateau of anti-mumps seroprevalence is lower. We attribute this result mainly to the lower population density in Lao PDR.
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