TcUBP-1, an mRNA destabilizing factor from trypanosomes, homodimerizes and interacts with novel AU-rich element- and Poly(A)-binding proteins forming a ribonucleoprotein complex.
Trypanosomes, protozoan parasites causing worldwide infections in human and animals, mostly regulate protein expression through post-transcriptional mechanisms and not at the transcription initiation level. We have previously identified a Trypanosoma cruzi RNA-binding protein named TcUBP-1. This protein is involved in mRNA destabilization in vivo through binding to AU-rich elements in the 3'-untranslated region of SMUG mucin mRNAs (D'Orso, I., and Frasch, A. C. (2001) J. Biol. Chem. 276, 34801-34809). In this work we show that TcUBP-1 is part of an approximately 450-kDa ribonucleoprotein complex with a poly(A)-binding protein and a novel 18-kDa RNA-binding protein, named TcUBP-2. Recombinant TcUBP-1 and TcUBP-2 proteins recognize U-rich RNAs with similar specificity and affinity through the approximately 92-amino acid RNA recognition motif. TcUBPs can homo- and heterodimerize in vitro through the glycine-rich C-terminal region. This interaction was also detected in vivo by co-immunoprecipitation of the ribonucleoprotein complex and using yeast two-hybrid assay. The poly(A)-binding protein identified was shown to disrupt the formation of TcUBP-1, but not TcUBP-2, homodimers in vitro. The possible role of TcUBP-1 ligands in the pathways that govern mRNA-stability and stage-specific expression in trypanosomes is discussed.
D'Orso
Ivan
I
Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús, CONICET-UNSAM, 1650 San Martin, Provincia de Buenos Aires, Argentina.
Frasch
Alberto C C
AC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019281:Dimerization; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D039102:Poly(A)-Binding Proteins / Q000378:metabolism*; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014349:Trypanosoma cruzi / Q000235:genetics / Q000378:metabolism*
D009838:Oligodeoxyribonucleotides; D039102:Poly(A)-Binding Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D010450:Endopeptidases; C059237:ubiquitin-Nalpha-protein hydrolase