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)

We cloned MAK11, MAK18, and MKT1 utilizing their genetic map positions. The MAK11 gene is close to CDC16 on chromosome XI. Both genes were cloned on a single 7-kb fragment, and both have now been sequenced. The MAK18 gene is located close to PET3 on chromosome VIII. A large plasmid carrying PET3 was obtained from R. Elder and R.E. Esposito and was found to also have the MAK18 gene. The MAK16 gene has been subcloned and sequenced starting with a clone provided by J. Crowley and D. Kaback. The MKT1 gene was mapped near the gene for topoisomerase II. The topoisomerase II clone was used as the starting point for chromosome-walking to isolate MKT1. A deletion-insertion mutation (disruption) of MKT1 results in an inability to maintain M2, but does not affect M1 or L-A maintenance. Clones of SKI3 and SKI8 were selected using the cold sensitivity for cell growth of ski- M1 strains. The SKI8 gene was disrupted and found to be nonessential for cell growth in the absence of M double-stranded RNA (dsRNA). The SKI3 and SKI8 genes were mapped using these clones. We have also obtained other clones suppressing the pathology caused by the high M titer in ski- strains. These clones are not the SKI genes themselves but somehow avoid the growth defect without repressing M copy number.
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PMID:Molecular characterization of chromosomal genes affecting double-stranded RNA replication in Saccharomyces cerevisiae. 355 12

Homologous recombination is a fundamental biological process. Biochemical understanding of this process is most advanced for Escherichia coli. At least 25 gene products are involved in promoting genetic exchange. At present, this includes the RecA, RecBCD (exonuclease V), RecE (exonuclease VIII), RecF, RecG, RecJ, RecN, RecOR, RecQ, RecT, RuvAB, RuvC, SbcCD, and SSB proteins, as well as DNA polymerase I, DNA gyrase, DNA topoisomerase I, DNA ligase, and DNA helicases. The activities displayed by these enzymes include homologous DNA pairing and strand exchange, helicase, branch migration, Holliday junction binding and cleavage, nuclease, ATPase, topoisomerase, DNA binding, ATP binding, polymerase, and ligase, and, collectively, they define biochemical events that are essential for efficient recombination. In addition to these needed proteins, a cis-acting recombination hot spot known as Chi (chi: 5'-GCTGGTGG-3') plays a crucial regulatory function. The biochemical steps that comprise homologous recombination can be formally divided into four parts: (i) processing of DNA molecules into suitable recombination substrates, (ii) homologous pairing of the DNA partners and the exchange of DNA strands, (iii) extension of the nascent DNA heteroduplex; and (iv) resolution of the resulting crossover structure. This review focuses on the biochemical mechanisms underlying these steps, with particular emphases on the activities of the proteins involved and on the integration of these activities into likely biochemical pathways for recombination.
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PMID:Biochemistry of homologous recombination in Escherichia coli. 796 21

Type II DNA topoisomerases are divided into two families, IIA and IIB. Types IIA and IIB enzymes share homologous B subunits encompassing the ATP-binding site, but have non-homologous A subunits catalyzing DNA cleavage. Type IIA topoisomerases are ubiquitous in Bacteria and Eukarya, whereas members of the IIB family are mostly present in Archaea and plants. Here, we report the detection of genes encoding type IIB enzymes in which the A and B subunits are fused into a single polypeptide. These proteins are encoded in several bacterial genomes, two bacterial plasmids and one archaeal plasmid. They form a monophyletic group that is very divergent from archaeal and eukaryotic type IIB enzymes (DNA topoisomerase VI). We propose to classify them into a new subfamily, denoted DNA topoisomerase VIII. Bacterial genes encoding a topoisomerase VIII are present within integrated mobile elements, most likely derived from conjugative plasmids. Purified topoisomerase VIII encoded by the plasmid pPPM1a from Paenibacillus polymyxa M1 had ATP-dependent relaxation and decatenation activities. In contrast, the enzyme encoded by mobile elements integrated into the genome of Ammonifex degensii exhibited DNA cleavage activity producing a full-length linear plasmid and that from Microscilla marina exhibited ATP-independent relaxation activity. Topoisomerases VIII, the smallest known type IIB enzymes, could be new promising models for structural and mechanistic studies.
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PMID:DNA topoisomerase VIII: a novel subfamily of type IIB topoisomerases encoded by free or integrated plasmids in Archaea and Bacteria. 2499 Mar 76