A candidate U1 small nuclear RNA for trypanosomatid protozoa.
In trypanosomatid protozoa, all mRNAs obtain identical 5'-ends by trans-splicing of the 5'-terminal 39 nucleotides of a small spliced leader RNA to appropriate acceptor sites in pre-mRNA. Although this process involves spliceosomal small nuclear (sn) RNAs, it is thought that trypanosomatids do not contain a homolog of the cis-spliceosomal U1 snRNA. We show here that a trypanosomatid protozoon, Crithidia fasciculata, contains a novel small RNA that displays several features characteristic of a U1 snRNA, including (i) a methylguanosine cap and additional 5'-terminal modifications, (ii) a potential binding site for common core proteins that are present in other trans-spliceosomal ribonucleoproteins, (iii) a U1-like 5'-terminal sequence, and (iv) a U1-like stem/loop I structure. Because trypanosomatid pre-mRNAs do not appear to contain cis-spliced introns, we argue that this previously unrecognized RNA species is a good candidate to be a trans-spliceosomal U1 snRNA.
Schnare
M N
MN
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada.
Gray
M W
MW
D000818:Animals; D001483:Base Sequence; D016831:Crithidia fasciculata / Q000235:genetics*; D008969:Molecular Sequence Data; D016053:RNA, Protozoan / Q000032:analysis* / Q000737:chemistry; D012342:RNA, Small Nuclear / Q000032:analysis* / Q000737:chemistry
D016053:RNA, Protozoan; D012342:RNA, Small Nuclear