The Role of 2', 5'-Oligoadenylate Synthetase Gene in Interferon System

点击翻译按钮获取中文摘要

2', 5'-Olioadenylate synthetase (OAS), an interferon (IFN)-induced enzyme, is activated by double-stranded RNA and synthesizes 2', 5'-oligoadenylate (2-5A) using ATP as a substrate. The following results were obtained from the research aided by this grant.(1) A P-loop motif followed by an Asp-containing sequence (referred to as D-box) and a region with a high content of Lys and Arg (KR-rich region) are conserved in various OAS subtypes. The experiments of the site-directed mutations into these motifs demonstrated that these motifs are important for the enzymatic activities of OAS : MgィイD12+ィエD1 binds to the D-box and ATP may interact to both P-loop and KR-rich region.(2) The gene for ChOAS is composed of 6 exons and 5 introns, in which the 6th exon encodes an ubiquitin-like (UbL) domain and the 1st to 5th exons encode the catalytic domain. The ChOAS gene has at least two alleles, OASィイD1*ィエD1A and OASィイD1*ィエD1B, and OASィイD1*ィエD1B allele was found only in Leghorn among various chicken lines. OAS-B has a deletion of 32-amino acids in the UbL domain.(3) When compared the enzymatic nature between OAS-A and B, OAS-B was more labile to heat-treatment and denatured at low temperature. Furthermore, OAS-B was more sensitive to protease-treatment and digested easily. These results indicate that the UbL domain stabilizes the conformation of the catalytic domain of this enzyme.(4) In addition to the above results, the target sites of IFN action in tissues were determined by the induction of OAS.