title: Pat1 contributes to the RNA binding activity of the Lsm1-7-Pat1 complex.
abstract: A major mRNA decay pathway in eukaryotes is initiated by deadenylation followed by decapping of the oligoadenylated mRNAs and subsequent 5'-to-3' exonucleolytic degradation of the capless mRNA. In this pathway, decapping is a rate-limiting step that requires the hetero-octameric Lsm1-7-Pat1 complex to occur at normal rates in vivo. This complex is made up of the seven Sm-like proteins, Lsm1 through Lsm7, and the Pat1 protein. It binds RNA and has a unique binding preference for oligoadenylated RNAs over polyadenylated RNAs. Such binding ability is crucial for its mRNA decay function in vivo. In order to determine the contribution of Pat1 to the function of the Lsm1-7-Pat1 complex, we compared the RNA binding properties of the Lsm1-7 complex purified from pat1Δ cells and purified Pat1 fragments with that of the wild-type Lsm1-7-Pat1 complex. Our studies revealed that both the Lsm1-7 complex and purified Pat1 fragments have very low RNA binding activity and are impaired in the ability to recognize the oligo(A) tail on the RNA. However, reconstitution of the Lsm1-7-Pat1 complex from these components restored these abilities. We also observed that Pat1 directly contacts RNA in the context of the Lsm1-7-Pat1 complex. These studies suggest that the unique RNA binding properties and the mRNA decay function of the Lsm1-7-Pat1 complex involve cooperation of residues from both Pat1 and the Lsm1-7 ring. Finally our studies also revealed that the middle domain of Pat1 is essential for the interaction of Pat1 with the Lsm1-7 complex in vivo.
authors.affiliation: Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
authors.forename: Ashis
authors.initials: A
authors.lastname: Chowdhury
authors.affiliation: Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
authors.forename: Swathi
authors.initials: S
authors.lastname: Kalurupalle
authors.affiliation: Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA tharun.sundaresan@usuhs.edu.
authors.forename: Sundaresan
authors.initials: S
authors.lastname: Tharun
mesh_terms: D000818:Animals; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D046912:Multiprotein Complexes / Q000378:metabolism; D030781:Organisms, Genetically Modified; D026723:Polyadenylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D039381:RNA Cap-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*
chemical_list: C114069:LSM1 protein, S cerevisiae; C521832:LSM7 protein, S cerevisiae; D046912:Multiprotein Complexes; C103266:PAT1 protein, S cerevisiae; D039381:RNA Cap-Binding Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins
keywords: Lsm1-7–Pat1 complex; Pat1; Sm-like proteins; decapping; mRNA decay