ABSTRACT
The rat Hst70 gene and its mouse counterpart Hsp70.2 are expressed specifically in pachytene primary spermatocytes and spermatids. Here we demonstrate that a 165 bp fragment of the Hst70 gene promoter, containing the T1 transcription start site region, entire exon 1 and 42 bp 5' region of the intron, is sufficient to drive testis-specific expression of the chloramphenicol acetyltransferase reporter gene in transgenic mice with the same developmentally regulated pattern as the endogenous Hsp70.2 gene. We show further that high-level tissue-specific gene expression requires additional sequences localized upstream of the T2 transcription start site. Electrophoretic mobility-shift assay analysis revealed that only testes of juvenile rats, when Hst70 gene expression is repressed, contain proteins that specifically bind to the Oct (octamer) sequence localized directly downstream of the T1 site.
Subject(s)
Gene Expression Regulation, Developmental , HSP70 Heat-Shock Proteins/genetics , Promoter Regions, Genetic/genetics , Response Elements/genetics , Testis/metabolism , Animals , Base Sequence , Cell Extracts , Cell Line, Tumor , Cell Nucleus/metabolism , DNA-Binding Proteins/metabolism , Electrophoretic Mobility Shift Assay , Exons/genetics , Genes, Reporter/genetics , Introns/genetics , Male , Mice , Mice, Transgenic , Octamer Transcription Factor-1 , Organ Specificity , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Reverse Transcriptase Polymerase Chain Reaction , Sp1 Transcription Factor/metabolism , Transcription Factors/metabolism , Transcription Initiation Site , Transgenes/geneticsABSTRACT
Heat shock activates in somatic cells a set of genes encoding heat shock proteins which function as molecular chaperones. The basic mechanism by which these genes are activated is the interaction of the specific transcription factor HSF1 with a regulatory DNA sequence called heat shock element (HSE). In higher eukaryotes HSF1 is present in unstressed cells as inactive monomers which, in response to cellular stress, aggregate into transcriptionally competent homotrimers. In the present paper we showed that the expression of a transgene encoding mutated constitutively active HSF1 placed under the control of a spermatocyte-specific promoter derived from the hst70 gene severely affects spermatogenesis. We found the testes of transgenic mice to be significantly smaller than those of wild-type males and histological analysis showed massive degeneration of the seminiferous epithelium. The lumen of tubules was devoid of spermatids and spermatozoa and using the TUNEL method we demonstrated a high rate of spermatocyte apoptosis. The molecular mechanism by which constitutively active HSF1 arrests spermatogenesis is not known so far. One can assume that HSF1 can either induce or repress so far unknown target genes involved in germ cell apoptosis.
