Pharmaceutical Sciences Faculty Publications
NKX3.1 Homeodomain Protein Binds to Topoisomerase I and Enhances its Activity
Document Type
Article
Publication Date
1-15-2007
Journal Title
Cancer Research
ISSN
0008-5472
Volume
67
Issue
2
First Page
455
Last Page
464
DOI
10.1158/0008-5472.CAN-06-1591
PubMed ID
17234752
Abstract
The prostate-specific homeodomain protein NKX3.1 is a tumor suppressor that is commonly down-regulated in human prostate cancer. Using an NKX3.1 affinity column, we isolated topoisomerase I (Topo I) from a PC-3 prostate cancer cell extract. Topo I is a class 1B DNA-resolving enzyme that is ubiquitously expressed in higher organisms and many prokaryotes. NKX3.1 interacts with Topo I to enhance formation of the Topo I-DNA complex and to increase Topo I cleavage of DNA. The two proteins interacted in affinity pull-down experiments in the presence of either DNase or RNase. The NKX3.1 homeodomain was essential, but not sufficient, for the interaction with Topo I. NKX3.1 binding to Topo I occurred independently of the Topo I NH2-terminal domain. The binding of equimolar amounts of Topo I to NKX3.1 caused displacement of NKX3.1 from its cognate DNA recognition sequence. Topo I activity in prostates of Nkx3.1+/- and Nkx3.1-/- mice was reduced compared with wild-type mice, whereas Topo I activity in livers, where no NKX3.1 is expressed, was independent of Nkx3.1 genotype. Endogenous Topo I and NKX3.1 could be coimmunoprecipitated from LNCaP cells, where NKX3.1 and Topo I were found to colocalize in the nucleus and comigrate within the nucleus in response to either gamma-irradiation or mitomycin C exposure, two DNA-damaging agents. This is the first report that a homeodomain protein can modify the activity of Topo I and may have implications for organ-specific DNA replication, transcription, or DNA repair.
Keywords
Cell line, tumor, chromatography, affinity, DNA topoisomerases, type I, DNA, neoplasm, enzyme activation, homeodomain proteins, kinetics, prostatic neoplasms, protein binding, transcription factors
Recommended Citation
Bowen, Cai; Stuart, August; Ju, Jeong-Ho; Tuan, Jenny; Blonder, Josip; Conrads, Thomas P.; Veenstra, Timothy D.; and Gelmann, Edward P., "NKX3.1 Homeodomain Protein Binds to Topoisomerase I and Enhances its Activity" (2007). Pharmaceutical Sciences Faculty Publications. 375.
https://digitalcommons.cedarville.edu/pharmaceutical_sciences_publications/375