A NOVEL HSP110-RELATED GENE, APG-1, THAT IS ABUNDANTLY EXPRESSED IN THE TESTIS RESPONDS TO A LOW-TEMPERATURE HEAT-SHOCK RATHER THAN THE TRADITIONAL ELEVATED-TEMPERATURES

We isolated a novel hsp110-related gene, apg-1, from a testis cDNA lib rary. The apg-1 transcripts were constitutively expressed in the testi cular germ cells and, in some degree, most tissues examined. In a mous e TAMA26 Sertoli cell line, apg-1 transcripts were induced in 2 h by a temperature shift from 32 to 39 degrees C, but not by a shift from 37 to 42 degrees C, the traditional heat stress, or a shift from 32 to 4 2 degrees C. The heat response pattern of hsp110 expression was simila r to that of apg-1. Although induction of a hsp70 transcript was obser ved in 2 h by a shift from 32 to 39 degrees C, the induction was more apparent by a shift from 37 to 42 degrees C or from 32 to 42 degrees C . Essentially similar differential response patterns were observed amo ng these genes in NIH/3T3 fibroblasts as well. The nuclear run-on assa y and the native gel mobility shift assay demonstrated that, by the 32 to 39 degrees C temperature shift, the apg-1 gene was transcriptional ly activated, and heat shock factor 1 bound to the heat shock elements in the 5'-flanking region of the apg-1 gene. These results demonstrat ed that expressions of apg-1, hsp110, and hsp70 could be heat-induced at a temperature lower than the traditional elevated temperatures in s omatic cells of both testis and nontestis origin and suggest that the mechanisms regulating the transcript levels of apg-1 and hsp110 are di fferent from those of hsp70. Furthermore, the constitutive expression in germ cells suggests that APG-1 plays a specific role in spermatogen esis as well as in stress response.