NKX3.1 Homeodomain Protein Binds to Topoisomerase I and Enhances Its Activity

Cai, Bin; Stuart, August; Ju, Jeong-Ho; Tuan, J A; Blonder, Josip; Conrads, Thomas P.; Veenstra, Timothy D.; Gelmann, Edward P.

doi:10.1158/0008-5472.can-06-1591

Cited by 42 publications

(56 citation statements)

References 42 publications

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“…2). The homeodomain of NKX3.1 is known to be involved in mediating the interaction with multiple protein partners, including prostate-derived Ets factor (25), serum response factor (32), Sp proteins (33), and topoisomerase I (20). The colocalization of NKX3.1 and GFP-TOPORS after MG132 treatment further supports their interaction in vivo.…”

Section: Discussionmentioning

confidence: 85%

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Ubiquitination by TOPORS Regulates the Prostate Tumor Suppressor NKX3.1

Guan

Pungaliya

et al. 2008

Journal of Biological Chemistry

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The NKX3.1 gene located at 8p21.2 encodes a homeodomaincontaining transcription factor that acts as a haploinsufficient tumor suppressor in prostate cancer. Diminished protein expression of NKX3.1 has been observed in prostate cancer precursors and carcinomas. TOPORS is a ubiquitously expressed E3 ubiquitin ligase that can ubiquitinate tumor suppressor p53. Here we report interaction between NKX3.1 and TOPORS. NKX3.1 can be ubiquitinated by TOPORS in vitro and in vivo, and overexpression of TOPORS leads to NKX3.1 proteasomal degradation in prostate cancer cells. Conversely, small interfering RNA-mediated knockdown of TOPORS leads to an increased steady-state level and prolonged half-life of NKX3.1. These data establish TOPORS as a negative regulator of NKX3.1 and implicate TOPORS in prostate cancer progression.Prostate cancer is the second leading cause of cancer deaths and the most frequently diagnosed malignancy in American men (1). Prostate carcinomas are considered to arise from cancer precursors including prostatic intraepithelial neoplasia (PIN) 2 and proliferative inflammatory atrophy (2). Molecular alterations, including hereditary and somatic gene mutations, gene deletions, gene amplification, chromosomal rearrangements, as well as epigenetic changes, have been implicated in prostate cancer initiation and progression (3).The NK class homeobox gene NKX3.1 has been studied extensively over the past decade for its roles in prostate development and carcinogenesis (4). The expression of the murine Nkx3.1 gene is androgen-dependent and is restricted largely to prostate epithelial cells in adults (5-7). Deletion of Nkx3.1 by gene targeting leads to prostate ductal morphological defects, as well as prostatic dysplasia and hyperplasia that resembles human PIN (8 -10). Interestingly, heterozygous Nkx3.1 mice also develop hyperplasia and PIN-like lesions (8). The human NKX3.1 gene maps to 8p21.2 within a region where loss of heterozygosity occurs in PIN and is common in prostate carcinomas; however, no mutations have been found in the coding region of the NKX3.1 allele remaining (11,12). In light of these observations, NKX3.1 has been proposed to function as a haploinsufficient tumor suppressor. In support of a dose-dependent growth regulatory function of NKX3.1, reduced but not complete loss of NKX3.1 protein expression is now well documented in most human prostate cancer samples in a manner inversely correlated with Gleason score (13) and also with disease progression (14). Diminished NKX3.1 expression is thought to be an early event in prostate carcinogenesis, and reduced NKX3.1 immunostaining was observed in most proliferative inflammatory atrophy and PIN lesions analyzed (13). The diminished NKX3.1 expression may be partly attributed to selective CpG methylation of the NKX3.1 promoter in some prostate cancer cases (15). Nevertheless, quantitative analyses of mRNA and protein levels of NKX3.1 in prostate carcinoma lesions revealed a lack of concordance between mRNA and protein levels (13). In particular, decre...

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Section: Discussionmentioning

confidence: 85%

“…NKX3.1 has recently been demonstrated to interact with topoisomerase I and enhance topoisomerase I DNA-unwinding activity (20). Topoisomerase I is thought to interact with the RING domain-containing protein TOPORS (21), which is known to interact with the tumor suppressor p53 (22) and later was found to ubiquitinate p53 (23).…”

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confidence: 99%

Ubiquitination by TOPORS Regulates the Prostate Tumor Suppressor NKX3.1

Guan

Pungaliya

et al. 2008

Journal of Biological Chemistry

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“…Androgen-responsive LNCaP cells (passage number [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] were propagated in RPMI1640 (Invitrogen, UK) medium supplemented with 10% heat-inactivated FBS (Invitrogen, UK). Cells were serum starved in the presence of 2% for 48 h and 0.5% for an additional 24 h in CT-FBS containing RPMI1640.…”

Section: Propagation and Androgen Inductionmentioning

confidence: 99%

“…TOPORS, a strong E3 ubiquitin ligase, promotes proteasomal degradation of NKX3.1 through direct interaction, predisposing cells to oncogenic transformation by providing an irreversible growth advantage as the first steps in prostate carcinogenesis [14]. Recently, it has been reported that NKX3.1 relocates to the nucleus and enhances the cleavage and re-ligation abilities of the topoisomerase I (topo I) enzyme through direct association [15,16]. ATM and ATR activities are influenced by NKX3.1 expression, which protects cells against IR-and mitomycin C-induced DNA damage [17].…”

Section: Introductionmentioning

confidence: 99%

NKX3.1 contributes to S phase entry and regulates DNA damage response (DDR) in prostate cancer cell lines

Erbaykent-Tepedelen

Özmen

Varisli

et al. 2011

Biochemical and Biophysical Research Communications

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NKX3.1 is an androgen-regulated homeobox gene that encodes a tissue-restricted transcription factor, which plays an important role in the differentiation of the prostate epithelium. Thus, the role of NKX3.1 as a functional topoisomerase I activity enhancer in cell cycle regulation and the DNA damage response (DDR) was explored in prostate cancer cell lines. As an early response to DNA damage following CPT-11 treatment, we found that there was an increase in the γH2AX (S139) foci number and that total phosphorylation levels were reduced in PC-3 cells following ectopic NKX3.1 expression as well as in LNCaP cells following androgen administration. Furthermore, upon drug treatment, the increase in ATM (S1981) phosphorylation was reduced in the presence of NKX3.1 expression, whereas DNA-PKcs expression was increased. Additionally, phosphorylation of CHK2 (T68) and NBS1 (S343) was abrogated by ectopic NKX3.1 expression, compared with the increasing levels in control PC-3 cells in a time-course experiment. Finally, NKX3.1 expression maintained a high cyclin D1 expression level regardless of drug treatment, while total γH2AX (S139) phosphorylation remained depleted in PC-3, as well as in LNCaP, cells. Thus, we suggest that androgen regulated NKX3.1 maintains an active DDR at the intra S progression and contributes to the chemotherapeutic resistance of prostate cancer cells to DNA damaging compounds.TUBITAK-106S200, -110S134, COST action BM0703 CANGENIN (TUBITAK -108S288); Turkish Scientific and Technological Research Council and BAP projects (06MUH004 and 10MUH006

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“…SRF 17, 21 , PDEF 14 , HDAC1 9 , SP1 13 , MYC 16 , and AR 18 ). In addition, NKX3.1 was shown to bind to and augment the activity of topoisomerase I, suggesting that it functions in DNA repair 22, 23 . NKX3.1 localizes to sites of DNA damage, promotes ATM and ATR activity, and enhances the survival of cells exposed to DNA damage 24 .…”

Section: Introductionmentioning

confidence: 99%

Systems analysis of the prostate tumor suppressor NKX3.1 supports roles in DNA repair and luminal cell differentiation

Yang

Chung²,

et al. 2014

F1000Res

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NKX3.1 is a homeobox transcription factor whose function as a prostate tumor suppressor remains insufficiently understood because neither the transcriptional program governed by NKX3.1, nor its interacting proteins have been fully revealed. Using affinity purification and mass spectrometry, we have established an extensive NKX3.1 interactome which contains the DNA repair proteins Ku70, Ku80, and PARP, thus providing a molecular underpinning to previous reports implicating NKX3.1 in DNA repair. Transcriptomic profiling of NKX3.1-negative prostate epithelial cells acutely expressing NKX3.1 revealed a rapid and complex response that is a near mirror image of the gene expression signature of human prostatic intraepithelial neoplasia (PIN). Pathway and network analyses suggested that NKX3.1 actuates a cellular reprogramming toward luminal cell differentiation characterized by suppression of pro-oncogenic c-MYC and interferon-STAT signaling and activation of tumor suppressor pathways. Consistently, ectopic expression of NKX3.1 conferred a growth arrest depending on TNFα and JNK signaling. We propose that the tumor suppressor function of NKX3.1 entails a transcriptional program that maintains the differentiation state of secretory luminal cells and that disruption of NKX3.1 contributes to prostate tumorigenesis by permitting luminal cell de-differentiation potentially augmented by defects in DNA repair.

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NKX3.1 Homeodomain Protein Binds to Topoisomerase I and Enhances Its Activity

Abstract: The prostate-specific homeodomain protein NKX3

Cited by 42 publications

References 42 publications

Ubiquitination by TOPORS Regulates the Prostate Tumor Suppressor NKX3.1

Ubiquitination by TOPORS Regulates the Prostate Tumor Suppressor NKX3.1

NKX3.1 contributes to S phase entry and regulates DNA damage response (DDR) in prostate cancer cell lines

Systems analysis of the prostate tumor suppressor NKX3.1 supports roles in DNA repair and luminal cell differentiation

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