Basis for regulated RNA cleavage by functional analysis of RNase L and Ire1p
RNase L and Ire1p are members of a superfamily of regulated endoribonucleases that play essential roles in mediating diverse types of cellular stress responses. 2′-5′ oligoadenylates, produced in response to interferon treatment and viral double-stranded RNA, are necessary to activate RNase L. In contrast, unfolded proteins in the endoplasmic reticulum activate Ire1p, a transmembrane serine/threonine kinase and endoribonuclease. To probe their similarities and differences, molecular properties of wild-type and mutant forms of human RNase L and yeast Ire1p were compared. Surprisingly, RNase L and Ire1p showed mutually exclusive RNA substrate specificity and partially overlapping but not identical requirements for phylogenetically conserved amino acid residues in their nuclease domains. A functional model for RNase L was generated based on the comparative analysis with Ire1p that assigns novel roles for ankyrin repeats and kinase-like domains.(Received November 20 2000)
(Revised December 4 2000)
(Accepted December 15 2000)
Key Words: interferon; ribonuclease; RNA stability; unfolded protein response.
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