title: Lariat structures are in vivo intermediates in yeast pre-mRNA splicing.
abstract: Transcripts from an ADC1-actin gene fusion containing the yeast actin intron are efficiently spliced in vivo. Four distinct forms of the excised actin intron are found in poly(A)- RNA from yeast carrying this transcription unit on a multicopy plasmid. Two of them migrate abnormally slowly in polyacrylamide gels, and one of these contains a block to reverse transcription at the conserved UACUAAC sequence (TACTAAC box). We also detect a larger RNA in the poly(A)+ fraction with abnormal gel mobility and the same reverse transcriptase block. Analysis of the major species of excised actin intron, labeled with 32P in vivo, reveals the presence of a branch at the third A in the UACUAAC sequence. This A is linked via a 3'-5' phosphodiester bond to the downstream C, and via a 2'-5' phosphodiester bond to a G, presumably from the 5' end of the intron. Thus this intron RNA is in the form of a lariat.
mesh_terms: D000199:Actins / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D005796:Genes; D005800:Genes, Fungal; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D009694:Nucleic Acid Precursors / Q000235:genetics*; D010957:Plasmids; D012322:RNA Precursors; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D000199:Actins; D009694:Nucleic Acid Precursors; D012322:RNA Precursors; D012333:RNA, Messenger; D004262:DNA Restriction Enzymes