title: Efficient mRNA polyadenylation requires a ubiquitin-like domain, a zinc knuckle, and a RING finger domain, all contained in the Mpe1 protein.
abstract: Almost all eukaryotic mRNAs must be polyadenylated at their 3' ends to function in protein synthesis. This modification occurs via a large nuclear complex that recognizes signal sequences surrounding a poly(A) site on mRNA precursor, cleaves at that site, and adds a poly(A) tail. While the composition of this complex is known, the functions of some subunits remain unclear. One of these is a multidomain protein called Mpe1 in the yeast Saccharomyces cerevisiae and RBBP6 in metazoans. The three conserved domains of Mpe1 are a ubiquitin-like (UBL) domain, a zinc knuckle, and a RING finger domain characteristic of some ubiquitin ligases. We show that mRNA 3'-end processing requires all three domains of Mpe1 and that more than one region of Mpe1 is involved in contact with the cleavage/polyadenylation factor in which Mpe1 resides. Surprisingly, both the zinc knuckle and the RING finger are needed for RNA-binding activity. Consistent with a role for Mpe1 in ubiquitination, mutation of Mpe1 decreases the association of ubiquitin with Pap1, the poly(A) polymerase, and suppressors of mpe1 mutants are linked to ubiquitin ligases. Furthermore, an inhibitor of ubiquitin-mediated interactions blocks cleavage, demonstrating for the first time a direct role for ubiquitination in mRNA 3'-end processing.
authors.affiliation: Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Susan D
authors.initials: SD
authors.lastname: Lee
authors.affiliation: Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, USA claire.moore@tufts.edu.
authors.forename: Claire L
authors.initials: CL
authors.lastname: Moore
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D000073718:Pancreatitis-Associated Proteins; D026723:Polyadenylation; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism; D054829:RING Finger Domains / Q000502:physiology*; D020871:RNA Stability; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D039221:mRNA Cleavage and Polyadenylation Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: C441449:Mpe1 protein, S cerevisiae; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; C429559:PAP1 protein, S cerevisiae; D011062:Polynucleotide Adenylyltransferase