title: The essential role for the RNA triphosphatase Cet1p in nuclear import of the mRNA capping enzyme Cet1p-Ceg1p complex of Saccharomyces cerevisiae.
abstract: mRNA capping is the first cotranscriptional modification of mRNA in the nucleus. In Saccharomyces cerevisiae, the first two steps of mRNA capping are catalyzed by the RNA triphosphatase Cet1p and the RNA guanylyltransferase Ceg1p. Cet1p and Ceg1p interact to form a mRNA capping enzyme complex and the guanylyltransferase activity of Ceg1p is stimulated by binding with Cet1p. The Cet1p-Ceg1p complex needs to be transported into the nucleus, where mRNA capping occurs. However, the molecular mechanism of nuclear transport of the Cet1p-Ceg1p complex is not known. Here, we show that Cet1p is responsible and that the Cet1p-Ceg1p interaction is essential for the nuclear localization of the Cet1p-Ceg1p complex. The results indicate that the Cet1p-Ceg1p interaction is important not only for the activation of Ceg1p, but also for nuclear import of the complex.
authors.affiliation: Laboratory of Basic Biology, Institute of Microbial Chemistry, Tokyo, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Takizawa
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Manabu
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Ayako
authors.initials: A
authors.lastname: Saito
authors.forename: Akira
authors.initials: A
authors.lastname: Fukao
authors.forename: Akio
authors.initials: A
authors.lastname: Nomoto
authors.forename: Kiyohisa
authors.initials: K
authors.lastname: Mizumoto
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000201:enzymology* / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D000098556:mRNA Guanylyltransferases
chemical_list: D009713:Nucleotidyltransferases; D000098556:mRNA Guanylyltransferases; D017766:Acid Anhydride Hydrolases; C023090:RNA triphosphatase