A DnaJ-like protein homologous to the yeast co-chaperone Sis1 (TcJ6p) is involved in initiation of translation in Trypanosoma cruzi.
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.
Salmon
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Instituto Oswaldo Cruz, Departamento de Bioquimica e Biologia Molecular, Av. Brasil 4365, 21045-900, Rio de Janeiro, Brazil.
Montero-Lomeli
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Goldenberg
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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*
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