title: Nonsense-mediated mRNA decay in Tetrahymena is EJC independent and requires a protozoa-specific nuclease.
abstract: Nonsense-mediated mRNA decay (NMD) is essential for removing premature termination codon-containing transcripts from cells. Studying the NMD pathway in model organisms can help to elucidate the NMD mechanism in humans and improve our understanding of how this biologically important process has evolved. Ciliates are among the earliest branching eukaryotes; their NMD mechanism is poorly understood and may be primordial. We demonstrate that highly conserved Upf proteins (Upf1a, Upf2 and Upf3) are involved in the NMD pathway of the ciliate, Tetrahymena thermophila. We further show that a novel protozoa-specific nuclease, Smg6L, is responsible for destroying many NMD-targeted transcripts. Transcriptome-wide identification and characterization of NMD-targeted transcripts in vegetative Tetrahymena cells showed that many have exon-exon junctions downstream of the termination codon. However, Tetrahymena may lack a functional exon junction complex (EJC), and the Tetrahymena ortholog of an EJC core component, Mago nashi (Mag1), is dispensable for NMD. Therefore, NMD is EJC independent in this early branching eukaryote.
authors.affiliation: Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.|College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.|Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna A-1030, Austria.
authors.forename: Miao
authors.initials: M
authors.lastname: Tian
authors.affiliation: Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.|College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Wentao
authors.initials: W
authors.lastname: Yang
authors.affiliation: Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.|College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: College of Life Sciences, Northwest Normal University, Lanzhou 730070, China.
authors.forename: Huai
authors.initials: H
authors.lastname: Dang
authors.affiliation: Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.|College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xingyi
authors.initials: X
authors.lastname: Lu
authors.affiliation: Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
authors.forename: Chengjie
authors.initials: C
authors.lastname: Fu
authors.affiliation: Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Miao
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D005091:Exons; D059365:Nonsense Mediated mRNA Decay; D015800:Protozoan Proteins / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism*; D016053:RNA, Protozoan / Q000378:metabolism; D012260:Ribonucleases / Q000502:physiology*; D016808:Tetrahymena thermophila / Q000201:enzymology / Q000235:genetics*; D059467:Transcriptome
chemical_list: D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D012260:Ribonucleases