Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in DNA superhelicity during DNA replication are mediated primarily by the activities of DNA helicases and topoisomerases. If these activities are defective, the progression of the replication fork can be hindered or blocked, which can lead to double-strand breaks, elevated recombination in regions of repeated DNA, and genome instability. Hereditary diseases like Werner's and Bloom's Syndromes are caused by defects in DNA helicases, and these diseases are associated with genome instability and carcinogenesis in humans. Here we report a Saccharomyces cerevisiae gene, MGS1 (Maintenance of Genome Stability 1), which encodes a protein belonging to the AAA(+) class of ATPases, and whose central region is similar to Escherichia coli RuvB, a Holliday junction branch migration motor protein. The Mgs1 orthologues are highly conserved in prokaryotes and eukaryotes. The Mgs1 protein possesses DNA-dependent ATPase and single-strand DNA annealing activities. An mgs1 deletion mutant has an elevated rate of mitotic recombination, which causes genome instability. The mgs1 mutation is synergistic with a mutation in top3 (encoding topoisomerase III), and the double mutant exhibits severe growth defects and markedly increased genome instability. In contrast to the mgs1 mutation, a mutation in the sgs1 gene encoding a DNA helicase homologous to the Werner and Bloom helicases suppresses both the growth defect and the increased genome instability of the top3 mutant. Therefore, evolutionarily conserved Mgs1 may play a role together with RecQ family helicases and DNA topoisomerases in maintaining proper DNA topology, which is essential for genome stability.
 ...
PMID:A yeast gene, MGS1, encoding a DNA-dependent AAA(+) ATPase is required to maintain genome stability. 1145 65

Cells of cultured line XL2 (Xenopus laevis) were synchronized by a combine effect of serum deprivation, aphidicolin, nocodazole and ALLN treatments. Four fractions were prepared, with maximum percentage of cells being in G1, S and G2 phases of cell cycle, and in mitosis, respectively. Comparative levels of six different proteins (beta-tubulin, DNA topoisomerase IIa, Xenopus Aurora A kinase pEg2, kinesin-like motor protein X1Eg5, and two members of condensis family proteins pEg7 (XCAP D2) and XCAP E were detected by quantitative Western blot analysis of these fractions. We used a new method of mathematic processing of data that commonly provides a possibility to calculate a comparative quantity of proteins in hypothetically "clean" fraction composed of cells being in the same phase of the cell cycle. This method makes it possible to use even partly synchronized cell cultures for analysis of changes in protein quantity, provided a precede determination of cell population composition is made.
 ...
PMID:[A comparative level of expression of some proteins in XL2 cell synchronized on different phases of cell cycle]. 1521 70

Most analyses of single-molecule experiments consist of binning experimental outcomes into a histogram and finding the parameters that optimize the fit of this histogram to a given data model. Here we show that such an approach can introduce biases in the estimation of the parameters, thus great care must be taken in the estimation of model parameters from the experimental data. The bias can be particularly large when the observations themselves are not statistically independent and are subjected to global constraints, as, for example, when the iterated steps of a motor protein acting on a single molecule must not exceed the total molecule length. We have developed a maximum-likelihood analysis, respecting the experimental constraints, which allows for a robust and unbiased estimation of the parameters, even when the bias well exceeds 100%. We demonstrate the potential of the method for a number of single-molecule experiments, focusing on the removal of DNA supercoils by topoisomerase IB, and validate the method by numerical simulation of the experiment.
 ...
PMID:Multiple events on single molecules: unbiased estimation in single-molecule biophysics. 1643 82

Myosin VI is an unconventional motor protein and functions in a variety of intracellular processes such as cell migration, vesicular trafficking, and homeostasis of the Golgi complex. Previously, we found that myosin VI is up-regulated in RKO, LS174T, and H1299 cells by DNA damage in a p53-dependent manner and mediates the pro-survival function of p53. Here, we showed that the levels of myosin VI protein were markedly inhibited in MCF7 and LNCaP cells by topoisomerase I-II inhibitors. However, the levels of myosin VI transcript were decreased only by topoisomerase I inhibitors. We also found that the levels of myosin VI protein were markedly inhibited in MCF7 cells by wild-type p53 but not tumor-derived mutant p53. Surprisingly, we found that the level of myosin VI transcript was slightly increased instead of decreased in MCF7 cells by p53, suggesting that a mechanism other than transcriptional repression is involved. Additionally, we found that on the myosin VI promoter, the level of acetylated histone H3 was markedly decreased, whereas that of p53 and acetylated histone H4 was slightly increased in MCF7 cells upon treatment with topoisomerase I-II inhibitors. Finally, we showed that overexpression of myosin VI enhances, whereas knockdown of myosin VI decreases, DNA damage-induced stabilization of p53, and consequently, knockdown of myosin VI de-sensitizes MCF7 cells to DNA damage-induced apoptosis. Taken together, as a mediator of the p53 pro-survival pathway and a marker of malignancy in some tumors, differential regulation of myosin VI in various tumor cells by topoisomerase inhibitors dictates whether knockdown of myosin VI inhibits, rather than enhances, the susceptibility of tumor cells to some therapeutic agents, which might be explored for designing a proper therapeutic strategy.
 ...
PMID:Myosin VI is differentially regulated by DNA damage in p53- and cell type-dependent manners. 2057 4