Abstract
Newly synthesized DNA in mammalian nuclei is concentrated in discrete nuclear granules called replication foci. These foci may be visualized using antibodies against 5-bromodeoxyuridine. In the early S-phase cells 100–250 foci are usually detected. On average, individual foci range between 0.5 and 2 µm in diameter and can be seen as clusters of more than ten average-sized (60–100 kb) synchronously activated replicons. In this study, employing minor modifications of the previous methods, we report the visualization of small replication foci of about 0.3 µm diameter (mini-foci). Some foci are clustered into folded chains consisting of 2–40 subunits. DNA content of one mini-focus is estimated to be 50–120 kb and there are 500–1500 mini-foci per cell in the early S-phase. Experimentally induced decrease in replicon size does not affect the size of mini-foci, suggesting that these represent elementary units of DNA replication in mammalian nuclei and are probably identical to the basic structural DNA loop domains.
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Tomilin, N., Solovjeva, L., Krutilina, R. et al. Visualization of elementary DNA replication units in human nuclei corresponding in size to DNA loop domains. Chromosome Res 3, 32–40 (1995). https://doi.org/10.1007/BF00711159
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DOI: https://doi.org/10.1007/BF00711159