IN-VITRO RNA EDITING-LIKE ACTIVITY IN A MITOCHONDRIAL EXTRACT FROM LEISHMANIA-TARENTOLAE

A mitochondrial extract from Leishmania tarentolae directs the incorpo ration of uridylate (U) residues within the pre-edited domain of synth etic cytochrome b (CYb) and NADH dehydrogenase subunit 7 mRNA. This ha s several characteristics of an in vitro RNA editing activity, but no direct evidence for involvement of guide RNAs was obtained. Inhibition by micrococcal nuclease suggests a requirement for some type of endog enous RNA. The limitation of internal U-incorporation to the pre-edite d region in the CYb mRNA and the inhibition by deletion or substitutio n of both mRNA anchor sequences for CYb gRNA-I and -II could be consis tent either with a gRNA-mediated process or a secondary structure-medi ated process. A low level of incorporation of [alpha-P-32]CTP occurs a t the same sites as UTP. Internal U-incorporation activity is selectiv ely inhibited by heterologous RNAs, suggesting an involvement of low a ffinity RNA-binding proteins which can be competed by the added RNA.