Expression of the testis-specific histone H1t gene: evidence for involvement of multiple cis-acting promoter elements

Abstract

The histone H1t gene is expressed exclusively in testis primary spermatocytes. Previous studies indicate that accumulation of H1t mRNA occurs 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 replication-dependent H1 promoters, the H1t promoter contains a unique TE element, and sequences within this element may contribute to enhanced expression of the gene in primary spermatocytes. Two imperfect inverted repeat sequences designated TE1 and TE2, that are located within the larger TE element, overlap a central GC-rich region and bind specifically to nuclear proteins derived from primary spermatocytes. Protein interactions characterized by methylation interference and UV cross-linking experiments indicate that a complex of proteins with a molecular mass of approximately 180 kDa binds TE1. The GC-rich region in H1t and in some replication dependent histone H1 promoters contains an Sp1 consensus sequence. Although the H1t/TE element that contains the GC-rich region binds nuclear proteins, it does not appear to bind Sp1 obtained from cell populations enriched in primary spermatocytes as determined by electrophoretic mobility supershift assays using polyclonal anti-Sp1 antibodies.

Germline-specific H1 variants: the “sexy” linker histones

“…TE is essential for H1t transcription in primary spermatocytes since its replacement by a heterologous DNA abolishes expression in transgenic mice (vanWert et al 1998). TE contains two inverted repeat sequences, TE1/X-box1 and TE2/X-box2, and a GC-box located between these two elements (Wolfe et al 1995). The TE/GC-box is a consensus-binding site for members of the Sp family of transcription factors.…”

Male germline-specific histones in mouse and man

“…These structures are necessary for mRNA processing and halflife regulation (Dominski and Marzluff, 1999). Analysis of the H1t promoter region (Wolfe et al, 1995) revealed a number of conserved elements found in other H1 genes as well as specific elements required for tissue-specific activation and repression of the H1t gene (Wolfe and Grimes, 1993). Grimes et al (2003) recently reviewed the mechanisms of the complex transcriptional regulation of the H1t gene.…”

Novel Repeat Elements Direct Rat Proenkephalin Transcription during Spermatogenesis

“…Both of these promoters function during spermatocyte and spermatid stages. In addition, testis-specific factors bind to regulatory elements (TE1 and TE2) unrelated to CREs within the spermatocytespecific histone H1t promoter (45). However, the identities and functional roles for these and other putative germ cell-specific trans-factors, such as Tet-1 (46), are generally unknown.…”

“…In both promoters, these sequences are located just upstream of the start sites, and in both cases, germ cell proteins bind to DNA segments containing these elements. Similarly, the testisspecific element TE2 found within the rat histone H1t promoter also contains sequences resembling the GCP1 repeats (CCCCAG) (45). It is therefore possible that sequences related to the repeat elements within GCP1 may regulate multiple germ cell-specific promoters expressed during late meiosis.…”