title: U1 small nuclear RNP from Trypanosoma brucei: a minimal U1 snRNA with unusual protein components.
abstract: Processing of primary transcripts in trypanosomes requires trans splicing and polyadenylation, and at least for the poly(A) polymerase gene, also internal cis splicing. The trypanosome U1 snRNA, which is most likely a cis-splicing specific component, is unusually short and has a relatively simple secondary structure. Here, we report the identification of three specific protein components of the Trypanosoma brucei U1 snRNP, based on mass spectrometry and confirmed by in vivo epitope tagging and in vitro RNA binding. Both T.brucei U1-70K and U1C are only distantly related to known counterparts from other eukaryotes. The T.brucei U1-70K protein represents a minimal version of 70K, recognizing the first loop sequence of U1 snRNA with the same specificity as the mammalian protein. The trypanosome U1C-like protein interacts with 70K directly and binds the 5' terminal sequence of U1 snRNA. Surprisingly, instead of U1A we have identified a novel U1 snRNP-specific protein, TbU1-24K. U1-24K lacks a known RNA-binding motif and integrates in the U1 snRNP via interaction with U1-70K. These data result in a model of the trypanosome U1 snRNP, which deviates substantially from our classical view of the U1 particle and may reflect the special requirements for splicing of a small set of cis-introns in trypanosomes.
authors.affiliation: Institut für Biochemie, Justus-Liebig-Universität Giessen Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Zsofia
authors.initials: Z
authors.lastname: Palfi
authors.forename: Bernd
authors.initials: B
authors.lastname: Schimanski
authors.forename: Arthur
authors.initials: A
authors.lastname: Günzl
authors.forename: Stephan
authors.initials: S
authors.lastname: Lücke
authors.forename: Albrecht
authors.initials: A
authors.lastname: Bindereif
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D013058:Mass Spectrometry; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000737:chemistry / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000378:metabolism*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics*
chemical_list: D015800:Protozoan Proteins; D016053:RNA, Protozoan; D012342:RNA, Small Nuclear; D017412:Ribonucleoprotein, U1 Small Nuclear; C405483:U1 small nuclear RNA