The structural and functional analysis of the human HSPA2 gene promoter region

HSPA2 is a human counterpart of the testis-specific rodent Hst70/Hsp70.2 gene. In contrast to the latter, the expression of the human HSPA2 gene is not limited to the testis, and recent data show that human tumor cells can express this gene at significant levels. The characteristics of HSPA2 expression suggests that it can influence the phenotype and survival of cancer cells similarly as overexpression of major members of the HSP70 gene family. Until now, neither the structure of the transcription unit of the human HSPA2 gene has been established nor a functional analysis of its promoter performed. In this study we established that the human HSPA2 gene, in contrast to its rodent counterparts, is intronless and has a single transcription start site. We also show that the same type of HSPA2 transcripts are synthesized in the testes and in cancer cell lines. In order to perform a functional study of the HSPA2 promoter, we used a transient transfection assay and found that the 392 bp fragment upstream of the ATG codon was a minimal region required for efficient transcription, while a 150 bp deletion from the 5' end of this region dramatically reduced the promoter activity. Delineation of the minimal promoter is a basic step toward identifiying the cis and trans elements involved in the regulation of the HSPA2 gene expression in cancer cells.