KSHV RNA-binding protein ORF57 inhibits P-body formation to promote viral multiplication by interaction with Ago2 and GW182

• Published in: Nucleic acids research Vol. 47; no. 17; pp. 9368 - 9385
• Main Authors: Sharma, Nishi R, Majerciak, Vladimir, Kruhlak, Michael J, Yu, Lulu, Kang, Jeong Gu, Yang, Acong, Gu, Shuo, Fritzler, Marvin J, Zheng, Zhi-Ming
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 26.09.2019
• Subjects: Argonaute Proteins - genetics; Autoantigens - genetics; DEAD-box RNA Helicases - genetics; Gene Expression Regulation, Viral - genetics; HeLa Cells; Herpesviridae Infections - genetics; Herpesviridae Infections - virology; Herpesvirus 8, Human - genetics; Herpesvirus 8, Human - pathogenicity; Host-Pathogen Interactions - genetics; Humans; Proto-Oncogene Proteins - genetics; RNA and RNA-protein complexes; RNA, Viral - genetics; RNA-Binding Proteins - genetics; Viral Regulatory and Accessory Proteins - genetics; Virus Replication - genetics
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gkz683

Cellular non-membranous RNA-granules, P-bodies (RNA processing bodies, PB) and stress granules (SG), are important components of the innate immune response to virus invasion. Mechanisms governing how a virus modulates PB formation remain elusive. Here, we report the important roles of GW182 and DDX6, but not Dicer, Ago2 and DCP1A, in PB formation, and that Kaposi's sarcoma-associated herpesvirus (KSHV) lytic infection reduces PB formation through several specific interactions with viral RNA-binding protein ORF57. The wild-type ORF57, but not its N-terminal dysfunctional mutant, inhibits PB formation by interacting with the N-terminal GW-domain of GW182 and the N-terminal domain of Ago2, two major components of PB. KSHV ORF57 also induces nuclear Ago2 speckles. Homologous HSV-1 ICP27, but not EBV EB2, shares this conserved inhibitory function with KSHV ORF57. By using time-lapse confocal microscopy of HeLa cells co-expressing GFP-tagged GW182, we demonstrated that viral ORF57 inhibits primarily the scaffolding of GW182 at the initial stage of PB formation. Consistently, KSHV-infected iSLK/Bac16 cells with reduced GW182 expression produced far fewer PB and SG, but 100-fold higher titer of infectious KSHV virions when compared to cells with normal GW182 expression. Altogether, our data provide the first evidence that a DNA virus evades host innate immunity by encoding an RNA-binding protein that promotes its replication by blocking PB formation.