EXPRESSION OF THE TESTIS-SPECIFIC HISTONE H1T GENE - EVIDENCE FOR INVOLVEMENT OF MULTIPLE CIS-ACTING PROMOTER ELEMENTS

The histone H1t gene is expressed exclusively in testis primary sperma tocytes. Previous studies indicate that accumulation of Hit mRNA occur s only in primary spermatocytes in normal rats and in transgenic mice bearing the rat H1t transgene. In this study, DNA sequences of human, monkey, mouse, and rat H1t genes were compared and found to be almost identical in the proximal promoter region extending from the H1/AC box through the TATAA box. In addition to conserved elements common to re plication-dependent H1 promoters, the Hit promoter contains a unique T E element, and sequences within this element may contribute to enhance d expression of the gene in primary spermatocytes. Two imperfect inver ted repeat sequences designated TE1 and TE2, that are located within t he larger TE element, overlap a central GC-rich region and bind specif ically to nuclear proteins derived from primary spermatocytes. Protein interactions characterized by methylation interference and UV cross-l inking experiments indicate that a complex of proteins with a molecula r mass of approximately 180 kDa binds TE1. The GC-rich region in H1t a nd in some replication dependent histone H1 promoters contains an Sp1 consensus sequence. Although the H1t/TE element that contains the GC-r ich region binds nuclear proteins, it does not appear to bind Sp1 obta ined from cell populations enriched in primary spermatocytes as determ ined by electrophoretic mobility supershift assays using polyclonal an ti-Sp1 antibodies.