title: RNAi interference of XPO1 and Sm genes and their effect on the spliced leader RNA in Trypanosoma brucei.
abstract: In trypanosomes, trans-splicing is a major essential RNA-processing mechanism that involves the addition of a spliced leader sequence to all mRNAs from a small RNA species, known as the spliced leader RNA (SL RNA). SL RNA maturation is poorly understood and it is not clear where assembly with Sm proteins takes place. In this study, we followed the localization of the SL RNA during knockdown of Sm proteins and XPO1, which in metazoa functions in transport of mRNA and U snRNAs from the nucleus to the cytoplasm. We found that XPO1 has no role in SL RNA biogenesis in wild-type cells, or when the cells are depleted of Sm proteins. During Sm depletion, 'defective' SL RNA lacking cap modification at position +4 first accumulates in the nucleus, suggesting that Sm assembly on SL RNA most probably takes place in this compartment. Only after massive nuclear accumulation is the 'defective' SL RNA exported to the cytoplasm to form SL RNP-C, which may be a route to dispose of SL RNA when its normal biogenesis is blocked.
authors.affiliation: The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Biton
authors.forename: Michal
authors.initials: M
authors.lastname: Mandelboim
authors.forename: Gil
authors.initials: G
authors.lastname: Arvatz
authors.forename: Shulamit
authors.initials: S
authors.lastname: Michaeli
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D001324:Autoantigens / Q000235:genetics / Q000502:physiology*; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D028884:Karyopherins / Q000235:genetics / Q000502:physiology*; D007700:Kinetics; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology; D016053:RNA, Protozoan / Q000032:analysis / Q000378:metabolism; D020038:RNA, Spliced Leader / Q000032:analysis / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000502:physiology*; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics / Q000502:physiology*; D020040:Trans-Splicing; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000502:physiology; D055517:snRNP Core Proteins; D000097606:Exportin 1 Protein
chemical_list: D001324:Autoantigens; D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D015800:Protozoan Proteins; D016053:RNA, Protozoan; D020038:RNA, Spliced Leader; D018160:Receptors, Cytoplasmic and Nuclear; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins; D000097606:Exportin 1 Protein; C038753:leptomycin B