Topoisomerase I (TOP1) Antibody – Mouse Monoclonal

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]

TOP1: 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 than 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. Regulates the alternative splicing of tissue factor (F3) pre-mRNA in endothelial cells. A chromosomal aberration involving TOP1 is found in a form of therapy-related myelodysplastic syndrome. Translocation t(11;20)(p15;q11) with NUP98. Belongs to the type IB topoisomerase family.

Protein type: Oncoprotein; Nucleolus; Isomerase; EC 5.99.1.2

Chromosomal Location of Human Ortholog: 20q12-q13.1

Cellular Component: nucleoplasm; nuclear chromosome; nucleolus; perikaryon; nucleus

Molecular Function: DNA topoisomerase (ATP-hydrolyzing) activity; protein binding; DNA binding; chromatin binding; DNA topoisomerase type I activity

Biological Process: circadian rhythm; response to drug; chromatin remodeling; DNA topological change; viral reproduction; programmed cell death; circadian regulation of gene expression; DNA replication; phosphorylation; embryonic cleavage; chromosome segregation