title: The yeast protein Xtc1 functions as a direct transcriptional repressor.
abstract: The yeast protein Xtc1 was identified as a protein that binds directly and specifically to the activation domains of acidic activators such as E2F-1, Gal4 and VP16. Additionally, it was shown to co-purify with the RNA polymerase II holoenzyme complex and it was suggested that Xtc1 functions as a regulator of transcription that modulates the response of RNA polymerase II to transcriptional activators. We have further analyzed the transcription function of Xtc1 and show that its fusion to a heterologous DNA binding domain can repress transcription of a reporter gene in vivo in an Srb10/11-dependent manner. We suggest that the presence of Xtc1 in the RNA polymerase II holoenzyme could help to recruit an Srb10-active form of the holoenzyme to target promoters. This same protein has also been implicated in mitochondrial DNA recombination, maintenance and repair. Determination of the subcellular localization using a GFP-Xtc1 fusion shows that it localizes to both the nucleus and the mitochondria in vivo, which is consistent with Xtc1 having a function in both cellular compartments.
authors.affiliation: Department of Molecular Genetics, Ruder BokoviM Institute, BijeniQka 54, 10000 Zagreb, Croatia.
authors.forename: Ana
authors.initials: A
authors.lastname: Traven
authors.forename: Lidija
authors.initials: L
authors.lastname: Staresincić
authors.forename: Milica
authors.initials: M
authors.lastname: Arnerić
authors.forename: Mary
authors.initials: M
authors.lastname: Sopta
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012319:RNA Polymerase II / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D016213:Cyclins; D020035:Holoenzymes; C417727:MHR1 protein, S cerevisiae; D009687:Nuclear Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C093345:SSN8 protein, S cerevisiae; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases; C498309:SSN3 protein, S cerevisiae; D012319:RNA Polymerase II