THE HUMAN 2',5'-OLIGOADENYLATE SYNTHETASE LOCUS IS COMPOSED OF 3 DISTINCT GENES CLUSTERED ON CHROMOSOME 12Q24.2 ENCODING THE 100-KDA, 69-KDA, AND 40-KDA FORMS

The 2',5'-oligoadenylate synthetases (OAS) represent a family of inter feron-induced proteins implicated in the mechanism of the antiviral ac tion of interferon. When activated by double-stranded RNA, these prote ins polymerize ATP into 2'-5'-linked oligomers with the general formul a pppA(2'p5'A)(n), n greater than or equal to 1. Three forms of human OAS corresponding to proteins of 40/46, 69/71, and 100 kDa have been d escribed. Based on the deduced amino acid sequences of the correspondi ng cDNAs, these OAS share a homologous region of about 350 amino acid residues that could represent the functional domain of GAS; the 40/46 proteins contain one single domain, whereas the 69/71- and the 100-kDa proteins contain two and three adjacent domains, respectively. Here w e show that the cDNAs for OAS-40/46, OAS-69/71, and OAS-100 hybridize to distinct interferon-induced mRNAs of 2 kb; 2.8, 3.3, 3.9, and 4.5 k b; and 7 kb, respectively. By in situ hybridization, we assign the hum an OAS-40/46, OAS-69/71, and OAS-100 genes (referred to as OAS1, OAS2, and OAS3, respectively) to a unique cytogenetic location on chromosom al region 12q24.2. We constructed a YAC, PAC, and cosmid contig carryi ng the three OAS genes and provide evidence that the three genes are c lustered within a single PAC clone of 130 kb. The three OAS genes are flanked by markers WI-10614 (cen) and D12S2293 (tel) and are contained within three sets of overlapping cosmid clones. They share the same o rientation of transcription and are arranged in the order cen- 5'-OAS1 -OAS3-OAS2-3'-tel. We suggest that clustering of these genes reflects their evolutionary relationship possibly through the duplication of th e conserved functional domain. This ready-to-sequence PAC and cosmid c ontig provides a valuable tool for identifying regulatory elements inv olved in the transcription of the OAS genes when induced by interferon and for elucidating the exon-intron organization of these genes. (C) 1998 Academic Press.