title: The transcription elongation factor Spt5 influences transcription by RNA polymerase I positively and negatively.
abstract: Spt5p is a universally conserved transcription factor that plays multiple roles in eukaryotic transcription elongation. Spt5p forms a heterodimer with Spt4p and collaborates with other transcription factors to pause or promote RNA polymerase II transcription elongation. We have shown previously that Spt4p and Spt5p also influence synthesis of ribosomal RNA by RNA polymerase (Pol) I; however, previous studies only characterized defects in Pol I transcription induced by deletion of SPT4. Here we describe two new, partially active mutations in SPT5 and use these mutant strains to characterize the effect of Spt5p on Pol I transcription. Genetic interactions between spt5 and rpa49Δ mutations together with measurements of ribosomal RNA synthesis rates, rDNA copy number, and Pol I occupancy of the rDNA demonstrate that Spt5p plays both positive and negative roles in transcription by Pol I. Electron microscopic analysis of mutant and WT strains confirms these observations and supports the model that Spt4/5 may contribute to pausing of RNA polymerase I early during transcription elongation but promotes transcription elongation downstream of the pause(s). These findings bolster the model that Spt5p and related homologues serve diverse critical roles in the control of transcription.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294-0024, USA.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Anderson
authors.forename: Martha L
authors.initials: ML
authors.lastname: Sikes
authors.forename: Yinfeng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sarah L
authors.initials: SL
authors.lastname: French
authors.forename: Shilpa
authors.initials: S
authors.lastname: Salgia
authors.forename: Ann L
authors.initials: AL
authors.lastname: Beyer
authors.forename: Masayasu
authors.initials: M
authors.lastname: Nomura
authors.forename: David A
authors.initials: DA
authors.lastname: Schneider
mesh_terms: D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D012318:RNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology; D035602:Transcriptional Elongation Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D009687:Nuclear Proteins; C080991:SPT4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D035602:Transcriptional Elongation Factors; C069940:SPT5 transcriptional elongation factor; D012319:RNA Polymerase II; D012318:RNA Polymerase I