title: Srb5/Med18-mediated termination of transcription is dependent on gene looping.
abstract: We have earlier demonstrated the involvement of Mediator subunit Srb5/Med18 in the termination of transcription for a subset of genes in yeast. Srb5/Med18 could affect termination either indirectly by modulating CTD-Ser(2) phosphorylation near the 3' end of a gene or directly by physically interacting with the cleavage and polyadenylation factor or cleavage factor 1 (CF1) complex and facilitating their recruitment to the terminator region. Here, we show that the CTD-Ser(2) phosphorylation pattern on Srb5/Med18-dependent genes remains unchanged in the absence of Srb5 in cells. Coimmunoprecipitation analysis revealed the physical interaction of Srb5/Med18 with the CF1 complex. No such interaction of Srb5/Med18 with the cleavage and polyadenylation factor complex, however, could be detected. The Srb5/Med18-CF1 interaction was not observed in the looping defective sua7-1 strain. Srb5/Med18 cross-linking to the 3' end of genes was also abolished in the sua7-1 strain. Chromosome conformation capture analysis revealed that the looped architecture of Srb5/Med18-dependent genes was abrogated in srb5(-) cells. Furthermore, Srb5-dependent termination of transcription was compromised in the looping defective sua7-1 cells. The overall conclusion of these results is that gene looping plays a crucial role in Srb5/Med18 facilitated termination of transcription, and the looped gene architecture may have a general role in termination of transcription in budding yeast.
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202, USA.
authors.forename: Banupriya
authors.initials: B
authors.lastname: Mukundan
authors.forename: Athar
authors.initials: A
authors.lastname: Ansari
mesh_terms: D015825:Chromosomes, Fungal / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal / Q000502:physiology*; D056892:Mediator Complex / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D061806:Transcription Termination, Genetic / Q000502:physiology*
chemical_list: D056892:Mediator Complex; D046912:Multiprotein Complexes; C082149:SRB5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins