title: Dcp1 links coactivators of mRNA decapping to Dcp2 by proline recognition.
abstract: Cap hydrolysis is a critical step in several eukaryotic mRNA decay pathways and is carried out by the evolutionarily conserved decapping complex containing Dcp2 at the catalytic core. In yeast, Dcp1 is an essential activator of decapping and coactivators such as Edc1 and Edc2 are thought to enhance activity, though their mechanism remains elusive. Using kinetic analysis we show that a crucial function of Dcp1 is to couple the binding of coactivators of decapping to activation of Dcp2. Edc1 and Edc2 bind Dcp1 via its EVH1 proline recognition site and stimulate decapping by 1000-fold, affecting both the K(M) for mRNA and rate of the catalytic step. The C-terminus of Edc1 is necessary and sufficient to enhance the catalytic step, while the remainder of the protein likely increases mRNA binding to the decapping complex. Lesions in the Dcp1 EVH1 domain or the Edc1 proline-rich sequence are sufficient to block stimulation. These results identify a new role of Dcp1, which is to link the binding of coactivators to substrate recognition and activation of Dcp2.
authors.affiliation: Program in Chemistry and Chemical Biology, University of California, San Francisco, California 94158, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Borja
authors.forename: Kirill
authors.initials: K
authors.lastname: Piotukh
authors.forename: Christian
authors.initials: C
authors.lastname: Freund
authors.forename: John D
authors.initials: JD
authors.lastname: Gross
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D004722:Endoribonucleases / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D011392:Proline / Q000235:genetics* / Q000378:metabolism; D039381:RNA Cap-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D012315:RNA Caps / Q000378:metabolism*; D020871:RNA Stability / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D011392:Proline; C100868:DCP1 protein, S cerevisiae; C400572:DCP2 protein, S cerevisiae; D004722:Endoribonucleases