1a35

Structural highlights

Disease

TOP1_HUMAN Note=A chromosomal aberration involving TOP1 is found in a form of therapy-related myelodysplastic syndrome. Translocation t(11;20)(p15;q11) with NUP98.

Function

TOP1_HUMAN 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.^{[1] [2] [3] [4]}

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

• Topoisomerase 3D structures

References

1. ↑ D'Arpa P, Machlin PS, Ratrie H 3rd, Rothfield NF, Cleveland DW, Earnshaw WC. cDNA cloning of human DNA topoisomerase I: catalytic activity of a 67.7-kDa carboxyl-terminal fragment. Proc Natl Acad Sci U S A. 1988 Apr;85(8):2543-7. PMID:2833744
2. ↑ Eisenreich A, Bogdanov VY, Zakrzewicz A, Pries A, Antoniak S, Poller W, Schultheiss HP, Rauch U. Cdc2-like kinases and DNA topoisomerase I regulate alternative splicing of tissue factor in human endothelial cells. Circ Res. 2009 Mar 13;104(5):589-99. doi: 10.1161/CIRCRESAHA.108.183905. Epub, 2009 Jan 22. PMID:19168442 doi:10.1161/CIRCRESAHA.108.183905
3. ↑ Interthal H, Quigley PM, Hol WG, Champoux JJ. The role of lysine 532 in the catalytic mechanism of human topoisomerase I. J Biol Chem. 2004 Jan 23;279(4):2984-92. Epub 2003 Oct 31. PMID:14594810 doi:10.1074/jbc.M309959200
4. ↑ Ioanoviciu A, Antony S, Pommier Y, Staker BL, Stewart L, Cushman M. Synthesis and mechanism of action studies of a series of norindenoisoquinoline topoisomerase I poisons reveal an inhibitor with a flipped orientation in the ternary DNA-enzyme-inhibitor complex as determined by X-ray crystallographic analysis. J Med Chem. 2005 Jul 28;48(15):4803-14. PMID:16033260 doi:10.1021/jm050076b