The role of stress proteins in the protein biosynthesis.

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1. Nagata and Morimoto collaborated to investigate the regulatory mechanism of the expression of stress proteins through heat shock transcription factor (HSF). Previously, HSF1 and HSF2 were identified and cloned. We have cloned a cDNA encoding a novel heat shock factor, HSF3, from the cDNA library of chick cells in addition to the chick homologues of human HSF1 and HSF2. HSF3 was activated by heat shock in chick erythrocytic cell line, but not in other chick cells. However, it has been revealed that HSF3 can synergistically cooperate with HSF1 in the activation of stress-induced transcription of stress proteins.2. Nagata and Hirayoshi investigated the interaction of collagen-specific stress protein, HSP47, with newly synthesized procollagens in the cells. The purpose of the study this year was focused to where the procollagen associates with and dissociates from HSP47 during its biosynthesis. It has been revealed that procollagen binds to HSP47 in the endplasmic reticulum (ER) immediately after the procollagen co-translationally enters the ER, and dissociates from HSP47 in the cis-golgi network after the procollagen is transported into the golgi area.3. Welch, Bensaude and Morimoto investigated the interaction of HSP70 with newly synthesized proteins as well as with HSFs. During the period of this project, it was figured out that HSP70 associates with activated DNA-binding HSF and renders the dissociation of HSF from the DNA resulting in the attenuation of the HSF activation after the completion of the induction of stress proteins including HSP70.