Interaction between DNA-damage protein GADD34 and a new member of the Hsp40 family of heat shock proteins that is induced by a DNA-damaging reagent

GADD34 is one of a subset of proteins induced after DNA damage or cell grow th arrest. To examine the function of GADD34, we used the yeast two-hybrid system to clone the protein that interacts with murine GADD34. As bait we u sed the product of the partial GADD34 cDNA, including the regions rich in p roline, glutamic acid, serine and threonine (PEST) and gamma (1)34.5 region s. A cDNA clone, named GAHSP40, which is a mouse DnaJ family protein with a high similarity to human HLJ1 was cloned. The interaction between GADD34 a nd GAHSP40 in cultured cells was confirmed by a co-immunoprecipitation expe riment and in NIH 3T3 cells by two-hybrid analysis in vivo. For binding of the two proteins, the gamma (1)34.5-similar region of GADD33 was necessary; however, the PEST region was also involved and the C-terminus of GAHSP40, but not the J-domain, was important. GAHSP40 was detected in all mouse tiss ues examined, but a different transcript was found in the testis. Both GADD 34 mRNA and GAHSP40 mRNA were significantly elevated by treatment with meth yl methanesulphonate, although the time courses were different. In addition , both GAHSP40 and GADD34 mRNA were induced by heat shock.