title: Role for gene looping in intron-mediated enhancement of transcription.
abstract: Intron-containing genes are often transcribed more efficiently than nonintronic genes. The effect of introns on transcription of genes is an evolutionarily conserved feature, being exhibited by such diverse organisms as yeast, plants, flies, and mammals. The mechanism of intron-mediated transcriptional activation, however, is not entirely clear. To address this issue, we inserted an intron in INO1, which is a nonintronic gene, and deleted the intron from ASC1, which contains a natural intron. We then compared transcription of INO1 and ASC1 genes in the presence and absence of an intron. Transcription of both genes was significantly stimulated by the intron. The introns have a direct role in enhancing transcription of INO1 and ASC1 because there was a marked increase in nascent transcripts from these genes in the presence of an intron. Intron-mediated enhancement of transcription required a splicing competent intron. Interestingly, both INO1 and ASC1 were in a looped configuration when their genes contained an intron. Intron-dependent gene looping involved a physical interaction of the promoter and the terminator regions. In addition, the promoter region interacted with the 5' splice site and the terminator with the 3' splice site. Intron-mediated enhancement of transcription was completely abolished in the looping defective sua7-1 strain. No effect on splicing, however, was observed in sua7-1 strain. On the basis of these results, we propose a role for gene looping in intron-mediated transcriptional activation of genes in yeast.
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Aboudi M
authors.initials: AM
authors.lastname: Moabbi
authors.forename: Neha
authors.initials: N
authors.lastname: Agarwal
authors.forename: Belal
authors.initials: B
authors.lastname: El Kaderi
authors.forename: Athar
authors.initials: A
authors.lastname: Ansari
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D054643:INDEL Mutation; D007438:Introns / Q000235:genetics*; D009154:Mutation; D007296:Myo-Inositol-1-Phosphate Synthase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D022821:RNA Splice Sites / Q000235:genetics; D012326:RNA Splicing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D013728:Terminator Regions, Genetic / Q000235:genetics; D035581:Transcription Factor TFIIB / Q000235:genetics; D015533:Transcriptional Activation
chemical_list: C111825:ASC1 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D004271:DNA, Fungal; D022821:RNA Splice Sites; C073680:SUA7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D035581:Transcription Factor TFIIB; D019204:GTP-Binding Proteins; C519641:INO1 protein, S cerevisiae; D007296:Myo-Inositol-1-Phosphate Synthase