Role of Kaposi’s Sarcoma-Associated Herpesvirus (KSHV) ORF57 Protein in Posttranscriptional Regulation of Viral Gene Expression

KSHV infection is associated with several human malignancies including Kaposi’s sarcoma, primary effusion lymphoma, and multicentric Castleman’s disease. Like other herpesviruses, KSHV has a large DNA genome encoding up to 100 genes that are expressed in a tightly regulated manner. We have identified KSHV ORF57 as a master regulator of KSHV gene expression that is essential for virus replication. ORF57 acts at the posttranscriptional level by enhancing stability, splicing, and translation of viral RNAs. We also found that these pleiotropic activities of ORF57 are mediated by its unique structure consisting of an intrinsically disordered N-terminal domain (NTD) and a structured C-terminal domain (CTD). This structural composition allows ORF57 to simultaneously interact with target RNAs and host cellular RNA-binding proteins via its NTD. We recently resolved the dimerized CTD structure of ORF57 at 3-angstrom resolution and are currently working on the structure of the ORF57 NTD complex with target RNAs.

Mapping of Viral Transcriptomes by Next-Generation Sequencing (NGS)

Viruses are intracellular parasites that use cellular machinery for the expression of viral proteins. However, the detailed architecture of the viral transcriptome remains poorly characterized. Using a combination of existing sequencing techniques and our newly developed NGS techniques, we performed comprehensive analyses of the viral transcriptomes of KSHV, EBV, HPV16, HPV18, MmuPV1, CRPV, etc. These data led to a better understanding of the host regulation of viral genome expression and viral pathogenesis.