title: The RNA helicase Mtr4p modulates polyadenylation in the TRAMP complex.
abstract: Many steps in nuclear RNA processing, surveillance, and degradation require TRAMP, a complex containing the poly(A) polymerase Trf4p, the Zn-knuckle protein Air2p, and the RNA helicase Mtr4p. TRAMP polyadenylates RNAs designated for decay or trimming by the nuclear exosome. It has been unclear how polyadenylation by TRAMP differs from polyadenylation by conventional poly(A) polymerase, which produces poly(A) tails that stabilize RNAs. Using reconstituted S. cerevisiae TRAMP, we show that TRAMP inherently suppresses poly(A) addition after only 3-4 adenosines. This poly(A) tail length restriction is controlled by Mtr4p. The helicase detects the number of 3'-terminal adenosines and, over several adenylation steps, elicits precisely tuned adjustments of ATP affinities and rate constants for adenylation and TRAMP dissociation. Our data establish Mtr4p as a critical regulator of polyadenylation by TRAMP and reveal that an RNA helicase can control the activity of another enzyme in a highly complex fashion and in response to features in RNA.
authors.affiliation: Center for RNA Molecular Biology & Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Huijue
authors.initials: H
authors.lastname: Jia
authors.forename: Xuying
authors.initials: X
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.forename: Ulf-Peter
authors.initials: UP
authors.lastname: Guenther
authors.forename: Sukanya
authors.initials: S
authors.lastname: Srinivasan
authors.forename: James T
authors.initials: JT
authors.lastname: Anderson
authors.forename: Eckhard
authors.initials: E
authors.lastname: Jankowsky
mesh_terms: D000241:Adenosine / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D026723:Polyadenylation; D017434:Protein Structure, Tertiary; D012331:RNA, Fungal / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D046912:Multiprotein Complexes; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae; C101004:MTR4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D000241:Adenosine