title: mRNA capping enzyme activity is coupled to an early transcription elongation.
abstract: One of the temperature-sensitive alleles of CEG1, a guanylyltransferase subunit of the Saccharomyces cerevisiae capping enzyme, showed 6-azauracil (6AU) sensitivity at the permissive growth temperature, which is a phenotype that is correlated with a transcription elongation defect. This temperature-sensitive allele, ceg1-63, has an impaired ability to induce PUR5 in response to 6AU treatment and diminished enzyme-GMP formation activity. However, this cellular and molecular defect is not primarily due to the preferential degradation of the transcript attributed to a lack of cap structure. Our data suggest that the guanylyltransferase subunit of the capping enzyme plays a role in transcription elongation as well as cap formation. First, in addition to the 6AU sensitivity, ceg1-63 is synthetically lethal with elongation-defective mutations in RNA polymerase II. Secondly, it produces a prolonged steady-state level of GAL1 mRNA after glucose shutoff. Third, it decreases the transcription read through a tandem array of promoter-proximal pause sites in an orientation-dependent manner. Taken together, we present direct evidence that suggests a role of capping enzyme in an early transcription. Capping enzyme ensures the early transcription checkpoint by capping of the nascent transcript in time and allowing it to extend further.
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Pharmacy, Sungkyunkwan University, Suwon, Kyonggi-do 440-746, South Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Seok-Ho
authors.initials: SH
authors.lastname: Jeong
authors.forename: Jeong-Hwa
authors.initials: JH
authors.lastname: Heo
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Jeong
authors.forename: Seong-Tae
authors.initials: ST
authors.lastname: Kim
authors.forename: Hong-Duk
authors.initials: HD
authors.lastname: Youn
authors.forename: Jeong-Whan
authors.initials: JW
authors.lastname: Han
authors.forename: Hyang-Woo
authors.initials: HW
authors.lastname: Lee
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Cho
mesh_terms: D000483:Alleles; D000963:Antimetabolites / Q000378:metabolism; D002455:Cell Division; D015966:Gene Expression Regulation, Fungal; D006801:Humans; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D012315:RNA Caps; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014158:Transcription, Genetic; D014498:Uracil / Q000031:analogs & derivatives* / Q000378:metabolism; D000098556:mRNA Guanylyltransferases
chemical_list: D000963:Antimetabolites; D021122:Protein Subunits; D012315:RNA Caps; D029701:Saccharomyces cerevisiae Proteins; D014498:Uracil; D009713:Nucleotidyltransferases; D000098556:mRNA Guanylyltransferases; C100248:azauracil