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D L Poccia

Publications and source records attributed to D L Poccia.

29 records · Page 2Linked to original sources
PubMed1989

Phosphorylation of sea urchin histone CS H2A.

Phosphorylation of cleavage stage (CS) histones was studied during the first cell cycle in male pronuclei of the sea urchin. Histone CS H2A rapidly incorporated 32PO4 during the replication period, but not before. Peptide mapping and amino acid analysis of radiolabelled CS H2A showed that phosphorylation occurred mainly on serine residues located in the C-terminal region of the molecule. When DNA replication was inhibited with aphidicolin both CS H2A and CS H2B accumulated in male pronuclei at the same rate as in the control culture, whereas accumulation of H3 and H4 histones was reduced. Incorporation of 32PO4 by CS H2A doubled when DNA synthesis was inhibited with aphidicolin. Thus phosphorylation of CS H2A was correlated with transport of CS histones from the egg storage pool to the male pronucleus, but not with chromatin synthesis, indicating that this event precedes nucleosome formation. A role for phosphorylation and dephosphorylation of the CS H2A C-terminal region in modulating transport of stored CS histone dimers and their assembly into nucleosomes is discussed.

Amino Acid Sequence↗
PubMed1988

Interaction of sperm histone variants and linker DNA during spermiogenesis in the sea urchin.

Several physical properties of sea urchin spermatid chromatin, which contains phosphorylated Sp H1 and Sp H2B histone variants, and mature sperm chromatin, in which these histones are dephosphorylated, were compared. Density, thermal stability, average nucleosomal repeat length, and resistance to micrococcal nuclease digestion are all increased in mature sperm relative to spermatid chromatin. Since the chromatins are identical in histone variant subtypes, the altered physical properties are not a consequence of changes in histone primary structure during spermiogenesis. The data are interpreted to mean that dephosphorylation of the N-terminal regions of Sp H1 and Sp H2B in late spermatid nuclei permits strong ionic binding of these highly basic regions to the extended linker, stabilizing the highly condensed structure of sperm chromatin.

Animals↗
PubMed1987

Transitions in histone variants during sea urchin spermatogenesis.

Transitions in the histone complement of nuclei during sea urchin spermatogenesis were investigated by two-dimensional gel electrophoresis. Nuclei were isolated from male gonads of individuals differing in degree of maturity. Unlike protamines, the sea urchin sperm-specific histone variants Sp H1 and Sp H2B appear early in spermatogenesis, well before spermatid differentiation, as the predominant representatives of their classes. Both proteins are phosphorylated from their first appearance until the last steps of spermiogenesis, when the highly condensed late spermatid nuclei become spermatozoan nuclei. Phosphorylation of serine occurs mostly (Sp H1) or entirely (Sp H2B) on the N-terminal portions of these molecules. We conclude that phosphorylated sperm-specific histone variants in the sea urchin function in spermatocytes during meiosis and are the major histones present during replication and transcription in some spermatogonia as well. We propose that the dephosphorylation of Sp H1 and Sp H2B in late spermatids is not primarily responsible for spermatid chromatin condensation but instead may act to stabilize the chromatin of the spermatozoon or aid in the final shaping of the sperm nucleus.

Animals↗
PubMed1985

Phosphorylation of sea urchin sperm H1 and H2B histones precedes chromatin decondensation and H1 exchange during pronuclear formation.

Immediately following fertilization in the sea urchin, sperm-specific histones Sp H1 and Sp H2B are phosphorylated. Then, in parallel with chromatin decondensation, nearly all phosphorylated Sp H1 is lost from the pronuclear chromatin, with the concurrent assimilation of the egg phosphoprotein CS H1. Chemical cleavage of in vivo labeled Sp H1 and Sp H2B shows that serine phosphorylation occurs in the unusually long N-terminal region of these proteins. These regions contain tandemly repeated tetra- and pentapeptide units each containing serine, proline, and two basic amino acids. It is proposed that sperm chromatin decondensation may require prior phosphorylation of these unusual N-terminal regions, whose function in the mature sperm may be to condense or stabilize its highly compact chromatin.

Amino Acid Sequence↗