2 TYPES OF CHICKEN 2',5'-OLIGOADENYLATE SYNTHETASE MESSENGER-RNA DERIVED FROM ALLELES AT A SINGLE-LOCUS

We have isolated two types of chicken 2',5'-oligoadenylate synthetase cDNAs, A and B, which encode predicted proteins of 508 amino acids (58 316 Da) and 476 amino acids (54336 Da), respectively. The region of A- protein comprising 33 amino acid residues from 385Ala to 417Cys is sub stituted by a single amino acid 385Tyr in B-protein. The homology betw een chicken and mammalian 2',5'-oligoadenylate synthetases is 49.5% ov er the amino-terminal 337 residues, Proteins expressed from A- and B-c DNAs in E. coli cells were both active in synthesizing 2',5'-oligoaden ylate. However, the activity of B-protein was 10-15% of that of A-prot ein. Southern blotting hybridization indicated that the chicken synthe tases are encoded by a single gene. RT-PCR and PCR analyses of RNA and DNA of chicken erythrocytes together with the sequence data of the PC R products showed that A-and B-mRNAs are derived from alleles at a sin gle locus encoding chicken 2',5'-oligoadenylate synthetase, designated as OAS A and OAS* B, Chickens carrying OAS* A/A produce two types of synthetase with molecular masses of 58 and 54 kDa, and those carrying OAS A/A produce only a single type of 58 kDa. (C) 1998 Elsevier Scie nce B.V.