The 2',5'-oligoadenylate synthetase (2-5OAS) is a enzyme that catalyzes syn
thesis of 2',5'-oligoadenylates (2-5A) in a dsRNA-dependent manner, and kno
wn as a major component of the IFN-induced host defense mechanisms against
microbial infections. Here, we report the presence of a novel 2-5OAS-like m
olecule, termed Oas15, in mice. The size of Oas15 cDNA was about 2 kb and e
ncoded a protein consisting of 362 aa. The amino acid sequence showed 76% s
imilarity to the mouse 2-5OAS, however, several motifs being important for
the enzyme activity were not conserved. The Oas15 mRNA was most significant
ly expressed in the brain, and relatively weak expression was found in othe
r organs such as the spleen, kidney, ovary and testis. It was also expresse
d in embryonic stem (ES) cells. The Oas15 mRNA expression in ES cells was e
levated 5-fold after treatment with IFN and about 2-fold in the brain when
stimulated with IFN inducer, polyinosinic-polycytidylic acid (poly[I:C]). I
n situ hybridization analysis revealed that Oas15 is expressed in neurons i
n the central nervous system in adult mice. When Oas15 was expressed in E.
coli, it yielded 42 kDa protein that binds to dsRNA, but it did not show ol
igoadenylate synthetase activity. These findings suggest a novel function o
f Oas15, which are independent of oligoadenylate synthetase activity, in th
e brain and developing embryos. (C) 2001 Elsevier Science B.V. All rights r
eserved.