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Publication Abstract from PubMed

Herpesviruses alternate between the latent and the lytic life cycle. Switching into the lytic life cycle is important for the herpesviral replication and disease pathogenesis. Activation of a transcription factor replication and transcription activator (RTA) has been demonstrated to govern this switch in KSHV. The protein encoded by open reading frame 49 from KSHV (ORF49KSHV) has been shown to up-regulate lytic replication in KSHV by enhancing the activities of the replication and transcription activator (RTA). We have solved the crystal structure of ORF49KSHV protein to a resolution of 2.4 A. ORF49KSHV protein has a novel fold consisting of 12 alpha helices bundled into two pseudo-domains. Most notably are distinct charged patches on the protein surface, which are possible protein-protein interaction sites. Homologs of ORF49KSHV protein in the gamma herpesvirus subfamily have low sequence similarities. Conserved residues are mainly located in the hydrophobic regions suggesting that they are more likely to play important structural roles rather than functional ones. Based on the identification and position of three sulfates binding to the positive areas, we performed some initial protein-DNA binding studies by analyzing the thermal stabilization of the protein in the presence of DNA. ORF49KSHV protein is stabilized in a dose-responsive manner by double stranded oligonucleotides suggesting actual DNA interaction and binding. Bio-layer interferometry studies also demonstrated that ORF49KSHV protein binds these oligonucleotides. IMPORTANCE: Kaposi's sarcoma associated herpesvirus (KSHV) is a tumorigenic gamma herpesvirus that causes multiple cancers and lymphoproliferative diseases. The virus exists mainly in the quiescent latent life cycle but when it is re-activated into the lytic life cycle, new viruses are produced and disease symptoms usually manifest. Several KSHV proteins play important roles in this re-activation but their exact roles are still largely unknown. In this study, we report the protein crystal structure of the open reading frame 49 encoded by KSHV (ORF49KSHV). Possible regions for protein interaction that could harbor functional importance were found on the protein surface of ORF49KSHV This led to the discovery of novel DNA binding properties by ORF49KSHV protein. Evolutionary conserved structural elements with the functional homologs of ORF49KSHV were also established with the structure.

Structure of the opening reading frame 49 protein encoded by Kaposi's sarcoma associated herpesvirus (KSHV).,Hew K, Veerappan S, Sim D, Cornvik T, Nordlund P, Dahlroth SL J Virol. 2016 Nov 2. pii: JVI.01947-16. PMID:27807232^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.