M1204, a novel 2′,5′ oligoadenylate synthetase with a ubiquitin-like extension, is induced during maturation of murine dendritic cells

A novel molecule expressed by spleen dendritic cells (DC) was isolated using a subtractive hybridization approach, The full-length M1204 clone has 3063 bp, with 1415 bp spanning a single open reading frame, coding for a protein of a predicted size of about 50 kDa, This sequence has strong homology to 2', 5' oligoadenylate synthetase and contains a ubiquitin-like domain. In Northern blot analyses the mRNA is strongly expressed in spleen DC, whereas, in bone marrow-derived DC, the amount of mRNA increases during the maturation process. None of the other leukocytes nor several hemopoietic cell lines tested express this mRNA, but clear expression occurs in many organs, the highest levels being in thymus, lung, and hone marrow. In situ hybridization, combined with immunocytochemical staining of tissue sections of lung and spleen, shows colocalization of M1204 vwith the 2Al and NLDC DC markers. In Western blot experiments, an antiserum raised against the recombinant M1204 recognizes a single band in bone marrow-derived DC and in the lung. The expressed oligoadenylate synthetase domain is active in synthesizing 2',5' diadenylate, which by itself may inhibit viral protein synthesis and may also function as a substrate for 2',5' oligaadenylate synthetase, Since the oligoadenylate/RNase L system provides early protection against virus infection, we hypothesize that M1204 prevents virus-induced cell death in DC.