The 5'-terminal region of the apocytochrome b transcript in Crithidia fasciculata is successively edited by two guide RNAs in the 3' to 5' direction.
We analyzed the chimeric guide RNA (gRNA)-mRNA molecules in Crithidia fasciculata that are predicted to transiently exist in editing of the 5'-terminal domain of apocytochrome b (CYb) mRNA, by polymerase chain reaction amplification and DNA sequencing, and obtained evidence suggesting that among the 14 editing sites numbered from 3' to 5', the sequence in the 3'-half of the sites (3' block) was specified by one guide RNA species (gRNA-I) and that in the remaining half of the sites (5' block) by the other guide RNA species (gRNA-II) and that the direction of editing in each block was 3' to 5'. The predicted transition site of editing by two gRNAs was between the first and second U residues from the 3' end within editing site 7. We found that a stretch of the edited sequence in the 3' block of mRNA could form a stable duplex with a stretch immediately upstream of the guide sequence in gRNA-II. The result leads to a successive editing model that the 3' block of pre-edited mRNA is first edited by gRNA-I, and after completion of editing, the 5' portion of gRNA-II pairs with the edited mRNA for editing of the 5' block.
Sugisaki
H
H
Institute for Chemical Research, Kyoto University, Japan.
Takanami
M
M
D000818:Animals; D001059:Apoproteins / Q000235:genetics*; D001482:Base Composition; D001483:Base Sequence; D002678:Chimera; D016831:Crithidia fasciculata / Q000235:genetics* / Q000378:metabolism; D003573:Cytochrome b Group / Q000235:genetics*; D045303:Cytochromes b; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D016133:Polymerase Chain Reaction / Q000379:methods; D017394:RNA, Guide, Kinetoplastida / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics*; D014158:Transcription, Genetic
D001059:Apoproteins; D003573:Cytochrome b Group; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D045303:Cytochromes b; D017394:RNA, Guide, Kinetoplastida