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The Flvr-encoded murine oligoadenylate synthetase 1b (Oas1b) suppresses 2-5A synthesis in intact cells.

ABSTRACT: Resistance to flavivirus-induced disease in mice is conferred by the autosomal gene Flv, identified as 2'-5' oligoadenylate synthetase 1b (Oas1b). Resistant mice express a full-length Oas1b protein while susceptible mice express the truncated Oas1btr. In this study, Oas1b was shown to be an inactive synthetase. Although the Oas/RNase L pathway was previously shown to have an antiviral role during flavivirus infections, Oas1b protein inhibited Oas1a in vitro synthetase activity in a dose-dependent manner and reduced 2-5A production in vivo in response to poly(I:C). These findings suggest that negative regulation of 2-5A by inactive Oas1 proteins may fine tune the RNase L response that if not tightly controlled could cause significant damage in cells. The results also indicate that flavivirus resistance conferred by Oas1b is not mediated by 2-5A. Instead, Oas1b inhibits flavivirus replication by an alternative mechanism that overrides the proviral effect of reducing 2-5A accumulation and RNase L activation.

SUBMITTER: Elbahesh H

PROVIDER: S-EPMC3046042 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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The Flvr-encoded murine oligoadenylate synthetase 1b (Oas1b) suppresses 2-5A synthesis in intact cells.

Elbahesh H H Jha B K BK Silverman R H RH Scherbik S V SV Brinton M A MA

Virology 20101105 2

Resistance to flavivirus-induced disease in mice is conferred by the autosomal gene Flv, identified as 2'-5' oligoadenylate synthetase 1b (Oas1b). Resistant mice express a full-length Oas1b protein while susceptible mice express the truncated Oas1btr. In this study, Oas1b was shown to be an inactive synthetase. Although the Oas/RNase L pathway was previously shown to have an antiviral role during flavivirus infections, Oas1b protein inhibited Oas1a in vitro synthetase activity in a dose-dependen ...[more]

PMID: 21056894

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Project description:BackgroundOligoadenylate synthetases (OASs) are widely distributed in Metazoa including sponges, fish, reptiles, birds and mammals and show large variation, with one to twelve members in any given species. Upon double-stranded RNA (dsRNA) binding, avian and mammalian OASs generate the second messenger 2'-5'-linked oligoadenylate (2-5A), which activates ribonuclease L (RNaseL) and blocks viral replication. However, how Metazoa shape their OAS repertoires to keep evolutionary balance to virus infection is largely unknown. We performed comprehensive phylogenetic and functional analyses of OAS genes from evolutionarily lower to higher Metazoa to demonstrate how the OAS repertoires have developed anti-viral activity and diversified their functions.ResultsAncient Metazoa harbor OAS genes, but lack both upstream and downstream genes of the OAS-related pathways, indicating that ancient OASs are not interferon-induced genes involved in the innate immune system. Compared to OASs of ancient Metazoa (i.e. sponge), the corresponding ones of higher Metazoa present an increasing number of basic residues on the OAS/dsRNA interaction interface. Such an increase of basic residues might improve their binding affinity to dsRNA. Moreover, mutations of functional residues in the active pocket might lead to the fact that higher Metazoan OASs lose the ability to produce 3'-5'-linked oligoadenylate (3-5A) and turn into specific 2-5A synthetases. In addition, we found that multiple rounds of gene duplication and domain coupling events occurred in the OAS family and mutations at functionally critical sites were observed in most new OAS members.ConclusionsWe propose a model for the expansion of OAS members and provide comprehensive evidence of subsequent neo-functionalization and sub-functionalization. Our observations lay the foundation for interrogating the evolutionary transition of ancient OAS genes to host defense genes and provide important information for exploring the unknown function of the OAS gene family.

Dataset Information

The Flvr-encoded murine oligoadenylate synthetase 1b (Oas1b) suppresses 2-5A synthesis in intact cells.

Publications

The Flvr-encoded murine oligoadenylate synthetase 1b (Oas1b) suppresses 2-5A synthesis in intact cells.

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