Interaction of HSF1 and HSF2 with the Hspa1b Promoter in Mouse Epididymal Spermatozoa1

Abstract

The Hspa1b gene is one of the first genes expressed after fertilization, with expression observed in the male pronucleus as early as the one-cell stage of embryogenesis. This expression can occur in the absence of stress and is initiated during the minor zygotic genome activation. There is a significant reduction in embryos developing to the blastocyte stage when HSPA1B levels are depleted, supporting the importance of this protein for embryonic viability. However, the mechanism responsible for allowing expression of Hspa1b during the minor ZGA is unknown. In this report, we investigated the role of HSF1 and HSF2 in bookmarking Hspa1b during late spermatogenesis. Western blots show that both HSF1 and HSF2 are present in epididymal spermatozoa and immunofluorescence analysis revealed that some of the HSF1 and HSF2 proteins in these cells overlap the DAPI-stained DNA region. Results from chromatin immunoprecipitation assays showed that HSF1, HSF2, and Sp1 are bound to the Hspa1b promoter in epididymal spermatozoa. Furthermore, we observed an increase in HSF2 binding to the Hspa1b promoter in late spermatids versus early spermatids suggesting a likely period during spermatogenesis when transcription factor binding could occur. These results support a model in which the binding of HSF1, HSF2, and Sp1 to the promoter of Hspa1b would allow the rapid formation of a transcription-competent state during the minor ZGA, thereby allowing Hspa1b expression.

Expressions of miR-15a and its target gene HSPA1B in the spermatozoa of patients with varicocele

“…HSPA1B belongs to HSP70 family and it is one of the most extensively studied heat inducible HSPs (Kampinga et al 2009, Stetler et al 2010, Scieglinska et al 2011. Recent studies have demonstrated that HSF1, HSF2, SP1, and RNA polymerase II are bound to the Hspa1b promoter in the mature spermatozoa of mice, allowing the rapid expression of this cytoprotective gene if the cells encounter stress (Xing et al 2005, Wilkerson et al 2008, Wilkerson & Sarge 2009. In this study, we elucidate the novel post-transcriptional regulation of HSPA1B by miR-15a, extend our knowledge of stress-induced heat-shock response pathway.…”

HSFs and regulation of Hsp70.1 (Hspa1b) in oocytes and preimplantation embryos: new insights brought by transgenic and knockout mouse models

“…This provides a functional dimension to the previous observations showing that HSF1 and HSF2 bind Hsp70.1 promoter in spermatozoa and are required for the proper chromatin organization in those gametes (Wilkerson et al 2008;Akerfelt et al 2008Akerfelt et al , 2010b. We first tested this paternal effect of HSF1 and HSF2 using one transgenic line (C1.101, Hsp70.1Luc), and it should be mentioned that transgene expression could be affected by the insertion site, which is, by itself, characterized by a defined chromatin environment.…”

“…It was shown that not only HSF1 and HSF2 are expressed during spermatogenesis (Alastalo et al 1998;Fiorenza et al 1995) but also that HSF1 or HSF2 loss of function have consequences on the chromatin organization of the spermatozoa (Akerfelt et al 2008;2010b). Furthermore it was hypothesized that the binding of HSF1 and HSF2 to the Hp70.1 promoter in spermatozoa would allow the early zygotic expression of Hsp70.1 (Wilkerson et al 2008). Therefore, to test this hypothesis, we combined transgenic (C1.101, Fig.…”

“…Based on competition experiments, this so-called constitutive, developmentally regulated expression was shown to involve HSF1 (Christians et al 1997). More recently, it was claimed that HSF1 and HSF2 would modified the chromatin organization of Hsp70.1 in spermatozoa and make the gene accessible to rapid transcription after fertilization at the time of the zygotic genome activation (ZGA) (Wilkerson et al 2008). Although other studies emphasized the role of HSF1 and HSF2 in the compaction of sperm genome (Akerfelt et al 2008;2010b), it remained to demonstrate how this intervention of HSFs functionally impacts gene expression at ZGA.…”

RNA polymerase II interacts with the Hspa1b promoter in mouse epididymal spermatozoa

“…Bookmarking Hspa1b during mitosis allows the rapid expression of this cytoprotective gene in early G1 if the cell encounters stress. Recently we extended those studies from tissue culture to spermatogenic cells and found that HSF1, HSF2, and SP1 are present in mature spermatozoa and bound to the Hspa1b promoter (Wilkerson et al 2008). Other reports have found that in mice HSF1 and HSF2 transcripts are present in preimplantation embryos as early as the one cell stage, while HSF1 and HSF2 proteins have been identified in 2 cell embryos (Christians et al 1997).…”