title: A mammalian pre-mRNA 5' end capping quality control mechanism and an unexpected link of capping to pre-mRNA processing.
abstract: Recently, we reported that two homologous yeast proteins, Rai1 and Dxo1, function in a quality control mechanism to clear cells of incompletely 5' end-capped messenger RNAs (mRNAs). Here, we report that their mammalian homolog, Dom3Z (referred to as DXO), possesses pyrophosphohydrolase, decapping, and 5'-to-3' exoribonuclease activities. Surprisingly, we found that DXO preferentially degrades defectively capped pre-mRNAs in cells. Additional studies show that incompletely capped pre-mRNAs are inefficiently spliced at all introns, a fact that contrasts with current understanding, and are also poorly cleaved for polyadenylation. Crystal structures of DXO in complex with substrate mimic and products at a resolution of up to 1.5Å provide elegant insights into the catalytic mechanism and molecular basis for their three apparently distinct activities. Our data reveal a pre-mRNA 5' end capping quality control mechanism in mammalian cells, indicating DXO as the central player for this mechanism, and demonstrate an unexpected intimate link between proper 5' end capping and subsequent pre-mRNA processing.
authors.affiliation: Department Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854, USA.
authors.forename: Xinfu
authors.initials: X
authors.lastname: Jiao
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Chang
authors.forename: Turgay
authors.initials: T
authors.lastname: Kilic
authors.forename: Liang
authors.initials: L
authors.lastname: Tong
authors.forename: Megerditch
authors.initials: M
authors.lastname: Kiledjian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D005095:Exoribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007438:Introns; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009843:Oligoribonucleotides / Q000378:metabolism; D011487:Protein Conformation; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012315:RNA Caps / Q000378:metabolism*; D034622:RNA Interference; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D013329:Structure-Activity Relationship; D013997:Time Factors; D014162:Transfection
chemical_list: C581516:Dom3Z protein, mouse; D009687:Nuclear Proteins; D009843:Oligoribonucleotides; D012315:RNA Caps; D012322:RNA Precursors; D005095:Exoribonucleases; C028793:5'-exoribonuclease; D011755:Pyrophosphatases