title: Small trypanosome RNA-binding proteins TbUBP1 and TbUBP2 influence expression of F-box protein mRNAs in bloodstream trypanosomes.
abstract: In the African trypanosome Trypanosoma brucei nearly all control of gene expression is posttranscriptional; sequences in the 3'-untranslated regions of mRNAs determine the steady-state mRNA levels by regulation of RNA turnover. Here we investigate the roles of two related proteins, TbUBP1 and TbUBP2, containing a single RNA recognition motif, in trypanosome gene expression. TbUBP1 and TbUBP2 are in the cytoplasm and nucleus, comprise ca. 0.1% of the total protein, and are not associated with polysomes or RNA degradation enzymes. Overexpression of TbUBP2 upregulated the levels of several mRNAs potentially involved in cell division, including the CFB1 mRNA, which encodes a protein with a cyclin F-box domain. CFB1 regulation was mediated by the 3'-untranslated region and involved stabilization of the mRNA. Depletion of TbUBP2 and TbUBP1 inhibited growth and downregulated expression of the cyclin F box protein gene CFB2; trans splicing was unaffected. The results of pull-down assays indicated that all tested mRNAs were bound to TbUBP2 or TbUBP1, with some preference for CFB1. We suggest that TbUBP1 and TbUBP2 may be relatively nonspecific RNA-binding proteins and that specific effects of overexpression or depletion could depend on competition between various different proteins for RNA binding.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Hartmann
authors.forename: Corinna
authors.initials: C
authors.lastname: Benz
authors.forename: Stefanie
authors.initials: S
authors.lastname: Brems
authors.forename: Louise
authors.initials: L
authors.lastname: Ellis
authors.forename: Van-Duc
authors.initials: VD
authors.lastname: Luu
authors.forename: Mhairi
authors.initials: M
authors.lastname: Stewart
authors.forename: Iván
authors.initials: I
authors.lastname: D'Orso
authors.forename: Christian
authors.initials: C
authors.lastname: Busold
authors.forename: Kurt
authors.initials: K
authors.lastname: Fellenberg
authors.forename: Alberto C C
authors.initials: AC
authors.lastname: Frasch
authors.forename: Mark
authors.initials: M
authors.lastname: Carrington
authors.forename: Jörg
authors.initials: J
authors.lastname: Hoheisel
authors.forename: Christine E
authors.initials: CE
authors.lastname: Clayton
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D049109:Cell Proliferation; D044783:F-Box Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D017125:Genes, Protozoan; D008018:Life Cycle Stages; D011485:Protein Binding; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D013347:Subcellular Fractions / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*
chemical_list: D020413:3' Untranslated Regions; D044783:F-Box Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D016601:RNA-Binding Proteins