title: A DnaJ-like protein homologous to the yeast co-chaperone Sis1 (TcJ6p) is involved in initiation of translation in Trypanosoma cruzi.
abstract: In eukaryotes, proteins homologous to the bacterial DnaJ protein are involved in regulation of the Hsp70 molecular chaperones, which are implicated in a variety of protein biogenesis pathways. We report herewith the molecular characterization of a T. cruzi DnaJ gene, termed TcJ6, encoding a protein that displays high sequence homology with the Saccharomyces cerevisiae Sis1 co-chaperone required for the initiation of translation. TcJ6 protein was expressed as a polypeptide of 36.5 kDa at a constant level during parasite differentiation and was associated to the cytoplasmic fraction. We showed that overexpression of TcJ6 complemented a temperature-sensitive yeast sis1 mutant. In addition, sucrose gradient sedimentation analysis of polysomes from T. cruzi and a yeast mutant overexpressing TcJ6p showed that the trypanosomal co-chaperone was closely associated with ribosomal subunits, 80 S monosomes and the smaller polysomes, as observed for Sis1p. Furthermore, in T. cruzi TcJ6p was also found to be preferentially concentrated around the nucleus, giving a speckled staining pattern. This suggests that TcJ6p is associated with the endoplasmic reticulum. Taken together, these data suggest that the trypanosomal DnaJ is involved in initiation of translation.
authors.affiliation: Instituto Oswaldo Cruz, Departamento de Bioquimica e Biologia Molecular, Av. Brasil 4365, 21045-900, Rio de Janeiro, Brazil.
authors.forename: D
authors.initials: D
authors.lastname: Salmon
authors.forename: M
authors.initials: M
authors.lastname: Montero-Lomeli
authors.forename: S
authors.initials: S
authors.lastname: Goldenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000502:physiology*; D010641:Phenotype; D014176:Protein Biosynthesis / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014349:Trypanosoma cruzi / Q000235:genetics*
chemical_list: D017931:DNA Primers; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010448:Peptide Initiation Factors; C070320:SIS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins