Structural and functional analysis reveals that human OASL binds dsRNA to enhance RIG-I signaling.Ibsen, M.S., Gad, H.H., Andersen, L.L., Hornung, V., Julkunen, I., Sarkar, S.N., Hartmann, R.
(2015) Nucleic Acids Res 43: 5236-5248
- PubMed: 25925578
- DOI: 10.1093/nar/gkv389
- Primary Citation of Related Structures:
- PubMed Abstract:
The oligoadenylate synthetase (OAS) enzymes are cytoplasmic dsRNA sensors belonging to the antiviral innate immune system. Upon binding to viral dsRNA, the OAS enzymes synthesize 2'-5' linked oligoadenylates (2-5As) that initiate an RNA decay pathway to impair viral replication ...
The oligoadenylate synthetase (OAS) enzymes are cytoplasmic dsRNA sensors belonging to the antiviral innate immune system. Upon binding to viral dsRNA, the OAS enzymes synthesize 2'-5' linked oligoadenylates (2-5As) that initiate an RNA decay pathway to impair viral replication. The human OAS-like (OASL) protein, however, does not harbor the catalytic activity required for synthesizing 2-5As and differs from the other human OAS family members by having two C-terminal ubiquitin-like domains. In spite of its lack of enzymatic activity, human OASL possesses antiviral activity. It was recently demonstrated that the ubiquitin-like domains of OASL could substitute for K63-linked poly-ubiquitin and interact with the CARDs of RIG-I and thereby enhance RIG-I signaling. However, the role of the OAS-like domain of OASL remains unclear. Here we present the crystal structure of the OAS-like domain, which shows a striking similarity with activated OAS1. Furthermore, the structure of the OAS-like domain shows that OASL has a dsRNA binding groove. We demonstrate that the OAS-like domain can bind dsRNA and that mutating key residues in the dsRNA binding site is detrimental to the RIG-I signaling enhancement. Hence, binding to dsRNA is an important feature of OASL that is required for enhancing RIG-I signaling.
Centre for Structural Biology, Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark firstname.lastname@example.org.