title: Trypanosoma brucei spliced leader RNA maturation by the cap 1 2'-O-ribose methyltransferase and SLA1 H/ACA snoRNA pseudouridine synthase complex.
abstract: Kinetoplastid flagellates attach a 39-nucleotide spliced leader (SL) upstream of protein-coding regions in polycistronic RNA precursors through trans splicing. SL modifications include cap 2'-O-ribose methylation of the first four nucleotides and pseudouridine (psi) formation at uracil 28. In Trypanosoma brucei, TbMTr1 performs 2'-O-ribose methylation of the first transcribed nucleotide, or cap 1. We report the characterization of an SL RNA processing complex with TbMTr1 and the SLA1 H/ACA small nucleolar ribonucleoprotein (snoRNP) particle that guides SL psi(28) formation. TbMTr1 is in a high-molecular-weight complex containing the four conserved core proteins of H/ACA snoRNPs, a kinetoplastid-specific protein designated methyltransferase-associated protein (TbMTAP), and the SLA1 snoRNA. TbMTAP-null lines are viable but have decreased SL RNA processing efficiency in cap methylation, 3'-end maturation, and psi(28) formation. TbMTAP is required for association between TbMTr1 and the SLA1 snoRNP but does not affect U1 small nuclear RNA methylation. A complex methylation profile in the mRNA population of TbMTAP-null lines indicates an additional effect on cap 4 methylations. The TbMTr1 complex specializes the SLA1 H/ACA snoRNP for efficient processing of multiple modifications on the SL RNA substrate.
authors.affiliation: Department of Microbiology, Immunology, & Molecular Genetics, University of California at Los Angeles, Los Angeles, CA 90095-1489, USA.
authors.forename: Jesse R
authors.initials: JR
authors.lastname: Zamudio
authors.forename: Bidyottam
authors.initials: B
authors.lastname: Mittra
authors.forename: Arnab
authors.initials: A
authors.lastname: Chattopadhyay
authors.forename: James A
authors.initials: JA
authors.lastname: Wohlschlegel
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Sturm
authors.forename: David A
authors.initials: DA
authors.lastname: Campbell
mesh_terms: D000818:Animals; D019751:Intramolecular Transferases / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D015800:Protozoan Proteins / Q000378:metabolism; D012315:RNA Caps / Q000378:metabolism*; D016053:RNA, Protozoan / Q000378:metabolism; D020537:RNA, Small Nucleolar / Q000378:metabolism*; D020038:RNA, Spliced Leader / Q000378:metabolism*; D012266:Ribose / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics*
chemical_list: D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D012315:RNA Caps; D016053:RNA, Protozoan; D020537:RNA, Small Nucleolar; D020038:RNA, Spliced Leader; D012266:Ribose; D008780:Methyltransferases; D019751:Intramolecular Transferases; C096995:pseudouridine synthases