title: The STAR protein QKI-7 recruits PAPD4 to regulate post-transcriptional polyadenylation of target mRNAs.
abstract: Emerging evidence has demonstrated that regulating the length of the poly(A) tail on an mRNA is an efficient means of controlling gene expression at the post-transcriptional level. In early development, transcription is silenced and gene expression is primarily regulated by cytoplasmic polyadenylation. In somatic cells, considerable progress has been made toward understanding the mechanisms of negative regulation by deadenylation. However, positive regulation through elongation of the poly(A) tail has not been widely studied due to the difficulty in distinguishing whether any observed increase in length is due to the synthesis of new mRNA, reduced deadenylation or cytoplasmic polyadenylation. Here, we overcame this barrier by developing a method for transcriptional pulse-chase analysis under conditions where deadenylases are suppressed. This strategy was used to show that a member of the Star family of RNA binding proteins, QKI, promotes polyadenylation when tethered to a reporter mRNA. Although multiple RNA binding proteins have been implicated in cytoplasmic polyadenylation during early development, previously only CPEB was known to function in this capacity in somatic cells. Importantly, we show that only the cytoplasmic isoform QKI-7 promotes poly(A) tail extension, and that it does so by recruiting the non-canonical poly(A) polymerase PAPD4 through its unique carboxyl-terminal region. We further show that QKI-7 specifically promotes polyadenylation and translation of three natural target mRNAs (hnRNPA1, p27(kip1)and β-catenin) in a manner that is dependent on the QKI response element. An anti-mitogenic signal that induces cell cycle arrest at G1 phase elicits polyadenylation and translation of p27(kip1)mRNA via QKI and PAPD4. Taken together, our findings provide significant new insight into a general mechanism for positive regulation of gene expression by post-transcriptional polyadenylation in somatic cells.
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Yamagishi
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tsusaka
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Mitsunaga
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Maehata
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan hoshino@phar.nagoya-cu.ac.jp.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Hoshino
mesh_terms: D000595:Amino Acid Sequence; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D059585:G1 Phase Cell Cycle Checkpoints / Q000235:genetics; D057809:HEK293 Cells; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008969:Molecular Sequence Data; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D011061:Poly A / Q000235:genetics* / Q000378:metabolism; D026723:Polyadenylation; D011062:Polynucleotide Adenylyltransferase; D054730:Protein Interaction Domains and Motifs; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D014162:Transfection; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism; D039221:mRNA Cleavage and Polyadenylation Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: C436291:CDKN1B protein, human; C495270:CTNNB1 protein, human; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D008055:Lipids; C086724:Lipofectamine; C490832:QKI protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D051176:beta Catenin; C000619656:hnRNPA1 protein, human; D039221:mRNA Cleavage and Polyadenylation Factors; D050760:Cyclin-Dependent Kinase Inhibitor p27; D011061:Poly A; D011062:Polynucleotide Adenylyltransferase; C550174:TENT2 protein, human