2 ',5 '-oligoadenylate synthetase gene in chicken: gene structure, distribution of alleles and their expression

We have cloned the gene for chicken 2',5'-oligoadenylate synthetase (ChOAS) by the method of polymerase chain reaction with use of ChOAS cDNA sequence . The ChOAS gene is composed of five introns and six exons containing all o f the sequence of the ChOAS cDNA from the start to the stop codon. The firs t five exons of ChOAS gene which encode the OAS catalytic domain have a sim ilar structure to HuOAS1 gene including the exon-intron boundaries. However , the length of introns of ChOAS gene is only 1/7 of those of HuOAS1 gene. The sixth exon of the ChOAS gene encodes the ubiquitin-like (UbL) domain of two consecutive sequence (UbL1 and UbL2) homologous to ubiquitin. ChOAS en coded in a single copy gene has at least two alleles, OAS*A and OAS*B. The differences between these two alleles are in the sixth exon of the gene; a 96-nucleotide sequence in the UbL1 portion of OAS*A is deleted from OAS*B. No OAS*B gene was detected in nine lines of chickens tested other than Legh orns. Almost the same levels of ChOAS-A and -B proteins induced physiologic ally in erythrocytes were detected in infant chickens (2-week-old), but in grown-up chickens (6-month-old) the level of erythrocyte OAS-B was markedly reduced in most of BIB chickens. Thus, the UbL domain of ChOAS is responsi ble for the maintenance of the OAS level in the tissue. (C) 2000 Elsevier S cience B.V. All rights reserved.