How cells achieve their final sizes is a pervasive biological question. One strategy to increase cell size is for the cell to amplify its chromosomal DNA content through endoreduplication cycles. Although endoreduplication is widespread in eukaryotes, we know very little about its molecular mechanisms. Successful progression of the endoreduplication cycle in Arabidopsis requires a plant homolog...

DNA topoisomerase (topo) II modulates DNA topology and is essential for cell division. There are two isoforms of topo II (a and b) that have limited functional redundancy, although their catalytic mechanisms appear the same. Using their COOHterminal domains (CTDs) in yeast two-hybrid analysis, we have identified phospholipid scramblase 1 (PLSCR1) as a binding partner of both topo II a and b. Al...

Topoisomerase IIalpha (topo IIalpha) is a nuclear enzyme involved in several critical processes, including chromosome replication, segregation and recombination. Previously we have shown that chromosomal protein HMGB1 interacts with topo IIalpha, and stimulates its catalytic activity. Here we show the effect of HMGB1 on the activity of the human topo IIalpha gene promoter in different cell line...

Topoisomerase II (topo II) is a ubiquitous enzyme that is essential for cell survival through its role in regulating DNA topology and chromatid separation. Topo II can be poisoned by common chemotherapeutics (such as doxorubicin and etoposide), leading to the accumulation of cytotoxic enzyme-linked DNA double-stranded breaks. In contrast, nonbreak-inducing topo II catalytic inhibitors have also...

We define a topo-system on group as set of subgroups satisfying certain topology-like conditions. study some fundamental properties groups equipped with (topo-groups) and using suitable formalization subgroup filter, we prove Tychonoff type theorem for the direct product topo-compact topo-groups.

The relative content of topoisomerase II (topo II) and the induction of topo-II-mediated DNA damage and cellular abnormalities have been characterized in developing spermatogenic cells of Xenopus laevis to gain an insight into the role of topo II during spermatogenesis. Decatenation assays identified topo II activity in nuclear extracts from spermatocytes and pre-elongate spermatids, but not in...

DNA topoisomerase I (Topo I) can exist in several different molecular weight forms in human leukemic cells. The Mr 98,000 form of Topo I was inhibited by several nucleoside triphosphates and their analogues at a 500 microM concentration in the order: dideoxy-GTP greater than 2-bromo-dATP greater than dideoxy-ATP greater than dideoxy-CTP greater than 2-fluoro-dATP greater than 2-chloro-dATP. The...

The acute effect of RNA and DNA synthesis inhibitors on DNA topoisomerase (topo) I localization within cells was examined. Indirect immunofluorescence revealed that topo I was distributed throughout the nuclei but was concentrated in nucleoli of untreated K562 leukemia cells and A549 non-small cell lung cancer cells. Treatment with the DNA polymerase inhibitor aphidicolin did not alter this dis...

The acute effect of RNA and DNA synthesis inhibitors on DNA topoisomerase (topo) I localization within cells was examined. Indirect imiminofluorescence revealed that topo I was distributed throughout the nuclei hut was concentrated in nucleoli of untreated K562 leukemia cells and A549 non-small cell lung cancer cells. Treatment with the DNA polymerase inhibitor aphidicolin did not alter this di...

Studies were conducted to determine the possible involvement of DNA topoisomerase II (Topo II) in the induction of differentiation in two human promyeloc)tic 111 (ill leukemia cell variants that are either sus ceptible or resistant to differentiation induced by phorbol-12-myristate13-acetate (I'M \). a protein kinase C activator. The acquisition of maturation markers and changes in the activity...