Identification of a transcriptional silencer in the protein-coding region of the mouse major inducible Hsp70 gene.

The mouse Hsp70.3 gene encodes the major inducible HSP70 protein and is located in close proximity to the Hsc70t gene, a testis-specific variant of the Hsp70 gene family. The two genes are arranged head-to-head, transcribed in divergent directions, and separated by approximately 600 base pairs. During transient expression analysis of the promoter for Hsc70t in mouse L cells, we have found that the Hsp70.3 coding region between -1844 and -800 relative to the transcription start site of Hsc70t possesses a silencer activity. The negative regulatory region containing this sequence also inhibited the expression from the heterologous simian virus 40 early promoter independently of orientation and position. It is possible that this silencer may not only be involved in testis-specific expression of Hsc70t but also function in down-regulation of Hsp70.3 induction.