Aliases for TOP1 Gene
External Ids for TOP1 Gene
Previous GeneCards Identifiers for TOP1 Gene
This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus altering the topology of DNA. This gene is localized to chromosome 20 and has pseudogenes which reside on chromosomes 1 and 22. [provided by RefSeq, Jul 2008]
GeneCards Summary for TOP1 Gene
TOP1 (Topoisomerase (DNA) I) is a Protein Coding gene. Diseases associated with TOP1 include molluscum contagiosum and irinotecan toxicity. Among its related pathways are Integrated Pancreatic Cancer Pathway and Apoptosis and survival Caspase cascade. GO annotations related to this gene include chromatin binding and DNA topoisomerase type II (ATP-hydrolyzing) activity. An important paralog of this gene is TOP1MT.
UniProtKB/Swiss-Prot for TOP1 Gene
Releases the supercoiling and torsional tension of DNA introduced during the DNA replication and transcription by transiently cleaving and rejoining one strand of the DNA duplex. Introduces a single-strand break via transesterification at a target site in duplex DNA. The scissile phosphodiester is attacked by the catalytic tyrosine of the enzyme, resulting in the formation of a DNA-(3-phosphotyrosyl)-enzyme intermediate and the expulsion of a 5-OH DNA strand. The free DNA strand then undergoes passage around the unbroken strand thus removing DNA supercoils. Finally, in the religation step, the DNA 5-OH attacks the covalent intermediate to expel the active-site tyrosine and restore the DNA phosphodiester backbone (By similarity). Regulates the alternative splicing of tissue factor (F3) pre-mRNA in endothelial cells. Involved in the circadian transcription of the core circadian clock component ARNTL/BMAL1 by altering the chromatin structure around the ROR response elements (ROREs) on the ARNTL/BMAL1 promoter.
Topoisomerases are ubiquitously expressed enzymes that overcome topological problems in genomic DNA, which can result from DNA replication, transcription and repair. Common problems such as overwinding (positive supercoiling), knots and tangles are resolved by topoisomerases by catalysing the breaking of one or two strands of DNA. Topoisomerase type I enzymes cut just one strand of the DNA double helix, and hence relax supercoiling of the DNA. Four genes encode Type I topoisomerases, which include nuclear topoisomerase I (TOP1) and mitochondrial topoisomerase I (TOP1MT). Type I enzymes can also be sub-divided into Types A and B based on their different catalytic mechanism for generating single DNA strand breaks. TOP1 and TOP1MT are both type 1B since they form 3'-phosphotyrosyl bonds. Camptothecin is a natural product inhibitor of TOP1 that has led to the discovery of derivatives that are clinically used anti-cancer drugs. Such inhibitors trap the enzyme in a cleavage complex with DNA. Type II topoisomerases (IIA and IIB) are particular important for the disentanglement of DNA, which is overcome by generating double stranded DNA breaks. Dysregulation of type II enzymes can therefore have a potentially significant genotoxic effect. There is a broad range of topoisomerase II inhibitors that are used clinically as anticancer agents.