KINETOPLASTID RNA-EDITING-ASSOCIATED PROTEIN-1 (REAP-1) - A NOVEL EDITING COMPLEX PROTEIN WITH REPETITIVE DOMAINS

Kinetoplastid RNA editing consists of the addition or deletion of urid ines at specific sites within mitochondrial mRNAs. This unusual RNA pr ocessing event is catalyzed by a ribonucleoprotein (RNP) complex that includes editing site-specific endoribonuclease, RNA ligase and termin al uridylnucleotidyl transferase (Tutase) among its essential enzymati c activities. To identify the components of this RNP, monoclonal antib odies were raised against partially purified editing complexes. One an tibody reacts with a mitochondrially located 45 kDa polypeptide (p45) which contains a conserved repetitive amino acid domain, p45 co-purifi es with RNA ligase and Tutase in a large (similar to 700 kDa) RNP, and anti-p45 antibody inhibits in vitro RNA editing. Thus, p45 is the fir st kinetoplastid RNA-editing-associated protein (REAP-1) that has been cloned and identified as a protein component of a functional editing complex.