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. 2012 Dec 20;4(2):142–154. doi: 10.1007/s13238-012-2088-4

Structural and biochemical studies of RIG-I antiviral signaling

Miao Feng 12088, Zhanyu Ding 22088, Liang Xu 12088, Liangliang Kong 22088, Wenjia Wang 12088, Shi Jiao 12088, Zhubing Shi 12088, Mark I Greene 32088, Yao Cong 22088,✉, Zhaocai Zhou 12088,✉
PMCID: PMC4875364  PMID: 23264040

Abstract

Retinoic acid-inducible gene I (RIG-I) is an important pattern recognition receptor that detects viral RNA and triggers the production of type-I interferons through the downstream adaptor MAVS (also called IPS-1, CARDIF, or VISA). A series of structural studies have elaborated some of the mechanisms of dsRNA recognition and activation of RIG-I. Recent studies have proposed that K63-linked ubiquitination of, or unanchored K63-linked polyubiquitin binding to RIG-I positively regulates MAVS-mediated antiviral signaling. Conversely phosphorylation of RIG-I appears to play an inhibitory role in controlling RIG-I antiviral signal transduction. Here we performed a combined structural and biochemical study to further define the regulatory features of RIG-I signaling. ATP and dsRNA binding triggered dimerization of RIG-I with conformational rearrangements of the tandem CARD domains. Full length RIG-I appeared to form a complex with dsRNA in a 2:2 molar ratio. Compared with the previously reported crystal structures of RIG-I in inactive state, our electron microscopic structure of full length RIG-I in complex with blunt-ended dsRNA, for the first time, revealed an exposed active conformation of the CARD domains. Moreover, we found that purified recombinant RIG-I proteins could bind to the CARD domain of MAVS independently of dsRNA, while S8E and T170E phosphorylation-mimicking mutants of RIG-I were defective in binding E3 ligase TRIM25, unanchored K63-linked polyubiquitin, and MAVS regardless of dsRNA. These findings suggested that phosphorylation of RIG inhibited downstream signaling by impairing RIG-I binding with polyubiquitin and its interaction with MAVS.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s13238-012-2088-4 and is accessible for authorized users.

Keywords: RIG-I, MAVS, antiviral signaling, polyubiquitin, phosphorylation

Electronic supplementary material

13238_2012_2088_MOESM1_ESM.pdf (784.2KB, pdf)

Supplementary material, approximately 784 KB.

Footnotes

These authors contributed equally to the work.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s13238-012-2088-4 and is accessible for authorized users.

Contributor Information

Yao Cong, Email: cong@sibcb.ac.cn.

Zhaocai Zhou, Email: zczhou@sibcb.ac.cn.

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Supplementary Materials

13238_2012_2088_MOESM1_ESM.pdf (784.2KB, pdf)

Supplementary material, approximately 784 KB.

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