title: The interaction of a Trypanosoma brucei KH-domain protein with a ribonuclease is implicated in ribosome processing.
abstract: Ribosomal RNA maturation is best understood in yeast. While substantial efforts have been made to explore parts of these essential pathways in animals, the similarities and uniquenesses of rRNA maturation factors in non-Opisthokonts remain largely unexplored. Eukaryotic ribosome synthesis requires the coordinated activities of hundreds of Assembly Factors (AFs) that transiently associate with pre-ribosomes, many of which are essential. Pno1 and Nob1 are two of six AFs that are required for the cytoplasmic maturation of the 20S pre-rRNA to 18S rRNA in yeast where it has been almost exclusively analyzed. Specifically, Nob1 ribonucleolytic activity generates the mature 3'-end of 18S rRNA. We identified putative Pno1 and Nob1 homologues in the protist Trypanosoma brucei, named TbPNO1 and TbNOB1, and set out to explore their rRNA maturation role further as they are both essential for normal growth. TbPNO1 is a nuclear protein with limited cytosolic localization relative to its yeast homologue. Like in yeast, it interacts directly with TbNOB1, with indications of associations with a larger AF-containing complex. Interestingly, in the absence of TbPNO1, TbNOB1 exhibits non-specific degradation activity on RNA substrates, and its cleavage activity becomes specific only in the presence of TbPNO1, suggesting that TbPNO1-TbNOB1 interaction is essential for regulation and site-specificity of TbNOB1 activity. These results highlight a conserved role of the TbPNO1-TbNOB1 complex in 18S rRNA maturation across eukaryotes; yet reveal a novel role of their interaction in regulation of TbNOB1 enzymatic activity.
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada.
authors.forename: Smriti
authors.initials: S
authors.lastname: Kala
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada; Department of Biochemistry, McGill University, McIntyre Medical Building, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada.
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Mehta
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada.
authors.forename: Chun Wai
authors.initials: CW
authors.lastname: Yip
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada; Department of Biochemistry, McGill University, McIntyre Medical Building, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada.
authors.forename: Houtan
authors.initials: H
authors.lastname: Moshiri
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada.
authors.forename: Hamed Shateri
authors.initials: HS
authors.lastname: Najafabadi
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada.
authors.forename: Ruoyu
authors.initials: R
authors.lastname: Ma
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada.
authors.forename: Najmeh
authors.initials: N
authors.lastname: Nikpour
authors.affiliation: Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN, 55812, USA.
authors.forename: Sara L
authors.initials: SL
authors.lastname: Zimmer
authors.affiliation: Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada; Department of Biochemistry, McGill University, McIntyre Medical Building, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada. Electronic address: reza.salavati@mcgill.ca.
authors.forename: Reza
authors.initials: R
authors.lastname: Salavati
mesh_terms: D002460:Cell Line; D004789:Enzyme Activation; D015870:Gene Expression; D020868:Gene Silencing; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D059367:RNA Cleavage; D034622:RNA Interference; D012337:RNA, Ribosomal, 18S / Q000235:genetics / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000502:physiology*
chemical_list: D015800:Protozoan Proteins; D012337:RNA, Ribosomal, 18S; D012260:Ribonucleases
keywords: 18S rRNA; Nuclease; RNA-binding; Ribosomal RNA; Trypanosome