On August 28, Science Advances published the latest research findings of Lan Ke’s research group on methionine oxidation of representative helicases online. Prof. Lan’s team is from the State Key Laboratory of Virology and College of Life Sciences, Wuhan University. The paper is entitled “Viperin catalyzes methionine oxidation to promote protein expression and function of helicases”.

This project was co-completed by Lan ke’s team from WHU and Feng Pinghui’s team from University of Southern California, USA. Their work, for the first time, reveals the protein substrates for Viperin, demonstrating the ubiquitous existence of methionine oxidation in various DNA and RNA helicases promotes their expression and functions. Prof. Lan Ke and Prof. Feng Pinghui are the co-corresponding authors. Bai Lei and Dong Jiazhen are co-first authors. The research is supported by the Natural Science Foundation for Distinguished Young Scholars, the Ministry of Science and Technology of China and some other institutions.

Kaposi’s sarcoma–associated herpesvirus (KSHV), of the human γ-herpesvirus family, is a large double-stranded DNA virus with a genome of ~165 kb. Like other herpesvirus, KSHV exists in two phases of its life cycle, a dominant latent phase and a transient lytic phase. Lytic replication is critical for viral progeny production and viral pathogenesis. Replicated viral genome templates late gene expression and is packaged into capsid to form infectious virion progeny. During lytic replication, KSHV encodes open reading frame 44 (ORF44) (KSHV helicase) to initiate viral DNA replication, although molecular detail of helicase regulation is missing. (from Viperin catalyzes methionine oxidation to promote protein expression and function of helicases, Science Advances 28 Aug 2019.)

 Viperin catalyzes methionine oxidation of KSHV helicases to promote viral DNA replication

Based on the KSHV model, researchers found the active interaction between KSHV helicase (ORF44) and Viperin (virus inhibitory protein, endoplasmic reticulum associated, interferon inducible). Further research showed Viperin catalyzed methionine oxidation of ORF44, whose oxidative site was later identified by mass spectrometry analysis, and other helicases. To examine the effects of individual methionine oxidative site, researchers engineered 11 mutants of KSHV helicase through site-directed mutagenesis and constructed 11 corresponding stable cell lines infected with this recombinant KSHV using BAC technology, concluding that viperin-induced methionine oxidation stabilizes protein expression and the replication of viral genomic DNA during KSHV lytic replication.

Helicases serves as a participant in a broad spectrum of fundamental biological processes, such as DNA replication, repair and innate immune sensing. However, the posttranslational modifications (PTMs) of helicases and its effects remain poorly understood, the researches on which are mainly about phosphorylation, ubiquitination, and SUMOylation. To examine if Viperin promoting methionine oxidation of KSHV helicase is generally effective, the site(s) of methionine oxidation in KSHV helicase and RNA helicase (RIG-I), researchers adopted DNA helicases (MCM7) and RIG-I. It turned out that that MCM7 and RIG-I interacted with Viperin. Mass spectrometry, which was then used to analyze methionine oxidative site(s) of the two proteins, indicated that methionine oxidation can promote protein expression and function of the above helicases.

Bibliography:

Viperin catalyzes methionine oxidation to promote protein expression and function of helicases

Science Advances 28 Aug 2019

Vol. 5, no. 8, eaax1031

DOI: 10.1126/sciadv.aax1031

Author: Yang Xue 

Rewritten by Zhou Siyan

Edited by Zhang Shiqi, Shen Yuxi and Hu Sijia