title: Visualization of elementary DNA replication units in human nuclei corresponding in size to DNA loop domains.
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 microns 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 micron 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.
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, St Petersburg.
authors.forename: N
authors.initials: N
authors.lastname: Tomilin
authors.forename: L
authors.initials: L
authors.lastname: Solovjeva
authors.forename: R
authors.initials: R
authors.lastname: Krutilina
authors.forename: C
authors.initials: C
authors.lastname: Chamberland
authors.forename: R
authors.initials: R
authors.lastname: Hancock
authors.forename: B
authors.initials: B
authors.lastname: Vig
mesh_terms: D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002877:Chromosomes, Human; D004247:DNA / Q000096:biosynthesis / Q000737:chemistry*; D004261:DNA Replication; D005455:Fluorescent Antibody Technique; D006801:Humans; D009690:Nucleic Acid Conformation; D012093:Replicon; D016196:S Phase
chemical_list: D004247:DNA