CHARACTERIZATION OF HDJ-2, A HUMAN 40 KD HEAT-SHOCK-PROTEIN

Heat shock proteins (HSP) are a large and complex family of proteins t hat play important roles in cellular function and survival. In previou s studies, cDNA for a 45 kD human HSP (HDJ-2) was cloned and shown to be homologous to DNA-J, a bacterial HSP [F.M. Ausubel, R. Brent, R. E. Kingston, D.D. Moore, J.G. Seidman, J.A. Smith, K. Struhl, Current Pr otocols in Molecular Biology, John Wiley and Sons, New York, 1997; A. Chellaiah, A. Davis, T. Mohanakumar, Cloning of a unique human homolog ue of the Escherichia coli DNAJ heat shock protein, Biochim. Biophys. Acta 1174 (1993) 111-113]. We have also shown that the expression of H DJ-2 is highly elevated in kidney allograft biopsies of kidneys underg oing rejection [Y.G. Alevy, D. Brennan. S. Durriya, T. Howard, T. Moha nakumar, Increased expression of the HDJ-2 heat shock protein in biops ies of human rejected kidneys, Transplantation 61 (1996) 963-967]. Bec ause of the potential importance of HDJ-2 to disease pathogenesis, we carried out studies to characterize the structure and regulation of HD J-2. Polyclonal and monoclonal antibodies that recognize recombinant H DJ-2 were prepared and used to localize its cellular expression. HDJ-2 was found to be farnesylated but not glycosylated. This HSP was ubiqu itously expressed in all of the cell types we analyzed and was localiz ed throughout the cytoplasm and around the nuclear membrane. However, upon heat shook it migrated to the Golgi, nucleolus, and the nuclear m embrane. Northern blot analysis revealed two mRNA transcripts whose sy nthesis was not affected by heat shock. In addition, Western blot anal ysis showed that expression of HDJ-2 was also not affected by heat sho ck. Thus, our study shows the characterization of a HSP which, because of its migration pattern upon heat shock, is an excellent candidate f or re protein chaperon. (C) 1998 Elsevier Science Ltd. All rights rese rved.