Histone H1 and the evolution of protamines




Lewis, John David MacLean

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It has been proposed that protamines have evolved vertically from an ancestral histone H1. My research has concentrated mainly on the investigation of this proposal by characterizing the sperm nuclear basic proteins (SNBPs) and their genes from a diverse range of organisms which employ histones, protamines, or protamine-like proteins to achieve sperm chromatin compaction. The complete gene sequences were obtained for the large histone H1-related protamine-like PL-I of the bivalve mollusc Spisula solidissima, the small protamine-like PL-III protein of related bivalve Mytilus californianus, and the protamine of the squid, Loligo opalescens, which is the first invertebrate protamine gene to be characterized. In addition, a full-length cDNA from the novel protamine and histone H1-related sperm nuclear protein of the primitive chordate, Styela montereyensis, was isolated and characterized. This genetic data, beyond providing valuable information on the regulation and organization of the heterogeneous family of SNBPs, has provided unequivocal support to the hypothesis that the chromatin-condensing protamines of the sperm have evolved from the chromatin-condensing histones of somatic cells. This has in turn allowed a more accurate tracing of the origin of histone H1, protamines and protamine-like proteins in both the protostomes and deuterostomes.