MABS2055-100UG Sigma-AldrichAnti-RNase L Antibody, clone 2E9

RNA decay in IFN-treated cells is controlled by 2'5'-linked oligoadenylate (2-5A)-dependent RNase (RNase L), a uniquely regulated endoribonuclease that requires short 5'-phosphorylated, 2-5A for its activity. Because RNase L is also implicated in the regulation of cell proliferation, we monitored its expression in colorectal adenocarcinomas and noncancerous polyps from familial adenomatous polyposis patients. Elevated levels of RNase L mRNA and activity were found in 17 of 20 tumors compared with corresponding normal mucosa. An mAb against RNase L revealed elevated amounts of this RNase in sections of the tumors, largely in the base of the villi. The occurrence of elevated levels of RNase L seems to be an early event in colorectal tumorigenesis, suggesting that control of RNA turnover is an important step in tumor progression. These data also indicate that regulating RNase L activity may be a useful strategy in treating colorectal carcinomas.

2-5A-dependent RNase is an interferon-inducible enzyme that requires 5'-phosphorylated, 2',5'-linked oligoadenylates (2-5A) for its endoribonuclease activity against single-stranded RNAs. We demonstrate here that recombinant, human 2-5A-dependent RNase forms stable homodimers during its stimulation by 2-5A. The protein dimers were observed to form only upon binding to 2-5A, as shown using gel filtration chromatography and chemical cross-linking and after centrifugation in glycerol gradients. A monoclonal antibody to 2-5A-dependent RNase was prepared and used to probe the subunit structure of the enzyme in the presence or absence of 2-5A. Using oligoadenylates of different length, structure, and 5'-phosphorylation states we determined that conversion of 2-5A-dependent RNase from its monomeric, inactive form to its homodimeric, active form required the presence of functional 2-5A. These results demonstrate that the catalytically active form of 2-5A-dependent RNase is a homodimer.