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S M Elsevier

Publications and source records attributed to S M Elsevier.

12 recordsLinked to original sources
PubMed1991

Processing of the precursor of protamine P2 in mouse. Peptide mapping and N-terminal sequence analysis of intermediates.

Protamine P2, the major basic chromosomal protein of mouse spermatozoa, is synthesized as a precursor almost twice as long as the mature protein, its extra length arising from an N-terminal extension of 44 amino acid residues. This precursor is integrated into chromatin of spermatids, and the extension is processed during chromatin condensation in the haploid cells. We have studied processing in the mouse and have identified two intermediates generated by proteolytic cleavage of the precursor. H.p.l.c. separated protamine P2 from four other spermatid proteins, including the precursor and three proteins known to possess physiological characteristics expected of processing intermediates. Peptide mapping indicated that all of these proteins were structurally similar. Two major proteins were further purified by PAGE, transferred to poly(vinylidene difluoride) membranes and submitted to automated N-terminal sequence analysis. Both sequences were found within the deduced sequence of the precursor extension. The N-terminus of the larger intermediate, PP2C, was Gly-12, whereas the N-terminus of the smaller, PP2D, was His-21. Both processing sites involved a peptide bond in which the carbonyl function was contributed by an acidic amino acid.

Amino Acid Sequence↗
PubMed1991

Processing of the precursor of protamine P2 in mouse. Identification of intermediates by their insolubility in the presence of sodium dodecyl sulfate.

Two basic proteins, protamines P1 and P2, are present in chromatin of mouse spermatozoa. Protamine P1, the less abundant protein in mouse, has a homolog in most mammals, and its synthesis follows a conventional route. In contrast, protamine P2 has been found only in certain other mammals, including humans, and it is synthesized as a precursor nearly twice as long as the mature protein. Processing of this precursor is not yet understood, although it necessarily takes place in elongating spermatids and is likely to play a role in the chromatin condensation occurring in these haploid cells. We have fractionated basic proteins from mouse testis chromatin and have identified six proteins on electrophoretic gels which, like protamines, are insoluble in SDS. All six were also soluble at the same trichloroacetic acid concentration as protamine P2 and were present in chromatin of elongating spermatids. Radioactive labelling patterns acquired by these SDS-insoluble proteins during translation in vitro of testis RNA indicate that the largest represents the precursor of protamine P2, and suggest that the others represent intermediates generated by proteolytic cleavage of the precursor. Results from pulse 3H labelling in vivo were also consistent with the conclusion that a precursor/product relationship exists between these proteins and protamine P2. Conclusions concerning the kinetics of processing have, in addition, been drawn from this data. Hypotheses concerning possible functional roles played by the precursor are presented.

Amino Acid Sequence↗
PubMed1978

Histone genes in macronuclear DNA of the ciliate Stylonychia mytilus.

DNA in the macronucleus of Stylonychia mytilus exists as discrete gene-sized fragments which are derived from micronuclear DNA through a series of well-defined developmental events. It has been proposed that each of the DNA fragments might represent a gene and its controlling elements. We have investigated this possibility using genes which code for the five histone proteins. Macronuclear DNA fragments were fractionated according to size by agarose gel electrophoresis, the fragments transferred to nitrocellulose filters using the technique of Southern, and the filter-bound DNA hybridized with labeled cloned histone genes of the sea urchin, Psammechinus miliaris. Results indicate, first, that sequences homologous to the five individual histone gene probes are present in discrete macronuclear fragments which appear as bands in the gel hybridization assay. Secondly, for each of the five individual histone gene probes the homologous DNA fragments are several in number, ranging in size in from 7.6 Kb (Kilo base pairs) to 0.73 Kb. For example, the largest of six detected fragments hybridizing to the H3 gene probe contains approximately 10 times the amount of DNA required to code for a Stylonychia H3 histone. The smallest detected fragment hybridizing to the H3 probe contains enought DNA to code for approximately two copies of the histone. Finally, in general, no two histone approximately two copies of the histone. Finally, in general, no two histone gene probes hybridized to the same macronuclear DNA fragment. This result indicates that genes coding for the five histones in Stylonychia are not located together on the same macronuclear DNA fragments and implies that the five functionally related genes would not be transcribed together as a polycistronic unit.

Animals↗
PubMed1976

Haploid genome reactivation and recovery by cell hybridization. Induction of DNA synthesis in spermatid nuclei.

DNA replication in haploid spermatid nuclei has been induced by hybridization of mouse early spermatids to proliferating HeLa cells. Use of polyethylene glycol rather than inactivated Sendai virus as the cell fusion agent was found to be essential to the production of large numbers of heterokaryons containing spermatid nuclei. DNA replication was detected in the heterokaryons by autoradiography. Density of silver grains over spermatid nucleic closely approximated the grain density over labelled HeLa nuclei in the same heterokaryons. Mouse centromeric heterochromatin appeared to be labelled last during the spermatid DNA synthetic period. On the average, HeLa nuclei in heterokaryons began DNA synthesis before spermatid nuclei. Results indicated, however, that DNA synthesis by HeLa nuclei might not be a prerequisite for spermatid DNA synthesis. These experiments demonstrate induction of DNA synthesis in spermatid nuclei, the first major step toward reactivation and recovery of their haploid genome by cell hybridization.

Animals↗
PubMed1975

Location of genes coding for 18S and 28S ribosomal RNA within the genome of Mus musculus.

Cytological detection of cistrons coding for 18S and 28S ribosomal RNA (rRNA) within the genome of Mus musculus inbred strain SEC/1ReJ was accomplished using the technique of in situ hybridization. Metaphase chromosome spreads prepared from cultured fetal mouse cells were stained with quinacrine-HCl and photographed. After destaining, they were hybridized to Xenopus laevis tritiated 18S and 28S rRNA, specific activity 7.5 X 10(6) dpm/mug. Silver grains clustered over specific chromosomes were readily apparent after 4 months of autoradiographic exposure. The identity of the labelled chromosomes was established by comparing the autoradiographs to quinacrine photographs showing characteristic fluorescent banding of the chromosomes in each metaphase spread. The 18S and 28S rRNA was found to hybridize to chromosomes 12, 18, and 16. Statistical analysis of the grain distribution over 26 spreads revealed that the three chromosomes were significantly labelled. Grains over these chromosomes were concentrated in an area immediately distal to the centromere, a region which in chromosomes 12 and 18 in this particular strain is the site of a secondary constriction. The relative size of the secondary constrictions, long and thus prominent on chromosome 12, obvious but shorter on 18, and indistinguishable on chromosome 16, correlated with the average number of grains observed over the centromeric region of these chromosomes, 2.5, 1.0, and 0.78, respectively.

Animals↗