During the elongating spermatid stage of spermiogenesis, human sperm chromatin undergoes a complex transition in which histones are extensively replaced by protamines in a carefully regulated transition including histone modifications and intermediate and temporary replacement of the histones by sperm-specific transition proteins. The replacement of most histones by protamines 1 and 2 facilitat...

The various sperm cell types present in a simple ejaculate differ in their motility and morphology. However, little is known about the nuclear maturity of these sperm cells and their relationship with morphological and motile characteristics. Protamines are considered a good marker of sperm nuclear maturity since they are added to the DNA in the last stage of spermatogenesis. We have analyzed t...

The characteristic morphogenetic changes which occur during sperm formation are at times accompanied by profound chemical alterations of the nuclear material. Thus it has been known since Miescher's pioneer studies during the 1870's (19) that nuclei in the immature salmon testis contain nucleohistones, while ripe salmon sperm contain nucleoprotamines. Basic proteins which are intermediate in co...

Mammalian spermiogenesis is marked by the morphological and functional differentiation of round haploid spermatids into mature spermatozoa. A molecular restructuring of the chromatin accompanies this process facilitated by the transition proteins and protamines which compact and condense the genetic material within the developing spermatid. Previous studies from this laboratory have demonstrate...

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The packaging of the male haploid genome within the differentiating spermatid nucleus is facilitated by small basic nuclear proteins called protamines. Although the majority of the DNA in human sperm chromatin is bound by these proteins, a small percentage retains a nucleosomal-like component. These histone-enriched regions may possess enhanced nuclease sensitivity and have been postulated to d...

During the haploid phase of mammalian spermatogenesis, nucleosomal chromatin is ultimately repackaged by small, highly basic protamines to generate an extremely compact, toroidal chromatin architecture that is critical to normal spermatozoal function. In common with several species, however, the human spermatozoon retains a small proportion of its chromatin packaged in nucleosomes. As nucleosom...

Despite their relatively arginine-rich composition, protamines exhibit a high degree of structural variation. Indeed, the primary structure of these histone H1-related sperm nuclear basic proteins (SNBPs) is not random and is the depository of important phylogenetic information. This appears to be the result of their fast rate of evolution driven by positive selection. The way by which the prot...