Anomalous RNA substrates for mammalian tRNA 3 ' processing endoribonuclease

Mammalian tRNA 3' processing endoribonuclease (3' tRNase) is an enzyme resp onsible for the removal of a 3' trailer from pre-tRNA, The enzyme can also recognize and cleave any target RNA that forms a pre-tRNA-like complex with another RNA. To investigate the interaction between 3' tRNase and substrat es, we tested various anomalous pre-tRNA-like complexes for cleavage by Dig 3' tRNase, We examined how base mismatches in the acceptor stem affect 3' tRNase cleavage of RNA complexes, and found that even one base mismatch in the acceptor stem drastically reduces the cleavage efficiency, Mammalian 3' tRNase was able to recognize complexes between target RNAs and 5'-half tDN As, and cleave the target RNAs, although inefficiently,,whereas the enzyme had no activity to cleave phosphodiester bonds of DNA, A relatively long RN A target, the Escherichia coli chloramphenicol acetyltransferase (CAT) mRNA , was cleaved by 3' tRNase in the presence of appropriate 5'-half tRNAs, We also demonstrated that an RNA complex of lin-4 and lin-IB from Caenorhabdi tis elegans can be recognized and cleaved by pig 3' tRNase. (C) 2000 Federa tion of European Biochemical Societies.