John H. Frenster, Sharon R. Landrum, Marilyn A. Masek, Shirley L.
Nakatsu, and Lennard S. Wilson.
Department of Medicine, Stanford University, Stanford, California
94305.
Abstract:
RNA synthesis decreases markedly during prophase to almost zero during metaphase, anaphase, and early telophase in normal mitotic cells. Localized openings of the DNA helix are necessary to allow strand-specific gene transcription within living cells (Cancer Res. 36: 3394 (1976), and the location, size, and number of these DNA helix openings can be determined within cells by a high-resolution electron-microscopic probe technique (Nature 248: 334 (1974). 126 normal and neoplastic mitotic cells within biopsied human bone marrow and lymph nodes were analyzed for the location, number, and size of DNA helix openings within each cell, and this data was then separately correlated with the ultrastructural stage of mitosis in each cell. All DNA helix openings were confined to the extended chromatin portion of the cell nucleus. The number of DNA helix openings decreased during early and late prophase, and became zero within normal cells during metaphase, anaphase, and early telophase, but did not become zero within neoplastic cells. The number of DNA helix openings increased in late telophase at a time when stable small nuclear RNA species return to post-mitotic daughter nuclei following the release of such RNA species to the cytoplasm earlier in mitosis (J. Cell Biol. 73: 322 (1977). Small nuclear RNA species may be important ligands in effecting DNA helix openings and inducing locus- and strand-specific gene transcription (Biochim. Biophys. Acta 475: 501 (1977). These quantitative single-cell data suggest that neoplastic mitotic cells may facilitate the transport of such RNA species to post-mitotic daughter cells.
Supported by NCI CA-10174 and CA-13524, by Am. Cancer Soc. IC-45, and by a Research Scholar Award from the Leukemia Society.
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