1RR8

Structural Mechanisms of Camptothecin Resistance by Mutations in Human Topoisomerase I

Summary for 1RR8

• Entry DOI: 10.2210/pdb1rr8/pdb
• Descriptor: 5'-D(*AP*AP*AP*AP*AP*GP*AP*CP*TP*T*GP*GP*AP*AP*AP*AP*AP*TP*TP*TP*TP*T)-3', 5'-D(*AP*AP*AP*AP*AP*TP*TP*TP*TP*TP*CP*CP*AP*AP*GP*TP*CP*TP*TP*TP*TP*T)-3', DNA topoisomerase I, ... (6 entities in total)
• Functional Keywords: protein-dna complex, topotecan, camptothecin, nucleic acid, human topoisomerase i, isomerase-dna complex, isomerase/dna
• Biological source: Homo sapiens (human)
• Cellular location: Nucleus, nucleolus: P11387
• Total number of polymer chains: 3
• Total formula weight: 81144.59

Authors

Chrencik, J.E.,Staker, B.L.,Burgin, A.B.,Stewart, L.,Redinbo, M.R. (deposition date: 2003-12-08, release date: 2004-07-06, Last modification date: 2024-10-30)

Primary citation

Chrencik, J.E.,Staker, B.L.,Burgin, A.B.,Pourquier, P.,Pommier, Y.,Stewart, L.,Redinbo, M.R.
Mechanisms of camptothecin resistance by human topoisomerase I mutations
J.Mol.Biol., 339:773-784, 2004

PubMed Abstract: Human topoisomerase I relaxes superhelical tension associated with DNA replication, transcription and recombination by reversibly nicking one strand of duplex DNA and forming a covalent 3'-phosphotyrosine linkage. This enzyme is the sole target of the camptothecin family of anticancer compounds, which acts by stabilizing the covalent protein-DNA complex and enhancing apoptosis through blocking the advancement of replication forks. Mutations that impart resistance to camptothecin have been identified in several regions of human topoisomerase I. We present the crystal structures of two camptothecin-resistant forms of human topoisomerase I (Phe361Ser at 2.6A resolution and Asn722Ser at 2.3A resolution) in ternary complexes with DNA and topotecan (Hycamtin), a camptothecin analogue currently in widespread clinical use. While the alteration of Asn722 to Ser leads to the elimination of a water-mediated contact between the enzyme and topotecan, we were surprised to find that a well-ordered water molecule replaces the hydrophobic phenylalanine side-chain in the Phe361Ser structure. We further consider camptothecin-resistant mutations at seven additional sites in human topoisomerase I and present structural evidence explaining their possible impact on drug binding. These results advance our understanding of the mechanism of cell poisoning by camptothecin and suggest specific modifications to the drug that may improve efficacy.

PubMed: 15165849
DOI: 10.1016/j.jmb.2004.03.077

Experimental method

X-RAY DIFFRACTION (2.6 Å)