Trypanosoma brucei J protein 2 is a stress inducible and essential Hsp40

Hsp40 proteins (also known as DnaJ or J proteins) serve as co-chaperones for Hsp70, but also display evidence of independent chaperone function. Furthermore, certain Hsp40s have been shown to be stress-inducible and essential. Trypanosomatids display a remarkable diversification of Hsp40 proteins, with numerous distinct Hsp40-like proteins encoded in the Trypanosoma brucei genome. This study investigated the role of one of the six T. brucei Type I Hsp40s, T. brucei J protein 2 (Tbj2). We found that Tbj2 was heat stress-inducible, and that knockdown using RNA interference resulted in a severe growth defect under normal growth temperatures. Furthermore, a green fluorescent protein (GFP)-Tbj2 fusion protein was found to be localized to the cytosol of T. brucei. Taken together, these data suggest that Tbj2 is not functionally equivalent to the other five Type I Hsp40s, and that it is an essential, cytosolic, and stress-inducible chaperone, potentially playing an important role in protein biogenesis in T. brucei.