Genome maintenance functions of a putative Trypanosoma brucei translesion DNA polymerase include telomere association and a role in antigenic variation

Maintenance of genome integrity is critical to guarantee transfer of an intact genome from parent to off-spring during cell division. DNA polymerases (Pols) provide roles in both replication of the genome and the repair of a wide range of lesions. Amongst replicative DNA Pols, translesion DNA Pols play a particular role: replication to bypass DNA damage. All cells express a range of translesion Pols, but little work has examined their function in parasites, including whether the enzymes might contribute to host-parasite interactions. Here, we describe a dual function of one putative translesion Pol in African trypanosomes, which we now name TbPolIE. Previously, we demonstrated that TbPolIE is associated with telomeric sequences and here we show that RNAi-mediated depletion of TbPolIE transcripts results in slowed growth, altered DNA content, changes in cell morphology, and increased sensitivity to DNA damaging agents. We also show that TbPolIE displays pronounced localization at the nuclear periphery, and that its depletion leads to chromosome segregation defects and increased levels of endogenous DNA damage. Finally, we demonstrate that TbPolIE depletion leads to deregulation of telomeric variant surface glycoprotein genes, linking the function of this putative translesion DNA polymerase to host immune evasion by antigenic variation

Choline Kinase Alpha as an Androgen Receptor Chaperone and Prostate Cancer Therapeutic Target.

BACKGROUND: The androgen receptor (AR) is a major drug target in prostate cancer (PCa). We profiled the AR-regulated kinome to identify clinically relevant and druggable effectors of AR signaling. METHODS: Using genome-wide approaches, we interrogated all AR regulated kinases. Among these, choline kinase alpha (CHKA) expression was evaluated in benign (n = 195), prostatic intraepithelial neoplasia (PIN) (n = 153) and prostate cancer (PCa) lesions (n = 359). We interrogated how CHKA regulates AR signaling using biochemical assays and investigated androgen regulation of CHKA expression in men with PCa, both untreated (n = 20) and treated with an androgen biosynthesis inhibitor degarelix (n = 27). We studied the effect of CHKA inhibition on the PCa transcriptome using RNA sequencing and tested the effect of CHKA inhibition on cell growth, clonogenic survival and invasion. Tumor xenografts (n = 6 per group) were generated in mice using genetically engineered prostate cancer cells with inducible CHKA knockdown. Data were analyzed with χ(2) tests, Cox regression analysis, and Kaplan-Meier methods. All statistical tests were two-sided. RESULTS: CHKA expression was shown to be androgen regulated in cell lines, xenografts, and human tissue (log fold change from 6.75 to 6.59, P = .002) and was positively associated with tumor stage. CHKA binds directly to the ligand-binding domain (LBD) of AR, enhancing its stability. As such, CHKA is the first kinase identified as an AR chaperone. Inhibition of CHKA repressed the AR transcriptional program including pathways enriched for regulation of protein folding, decreased AR protein levels, and inhibited the growth of PCa cell lines, human PCa explants, and tumor xenografts. CONCLUSIONS: CHKA can act as an AR chaperone, providing, to our knowledge, the first evidence for kinases as molecular chaperones, making CHKA both a marker of tumor progression and a potential therapeutic target for PCa.This work was supported by a Cancer Research UK program grant (to DEN) and also by the US Department of Defense (Prostate Cancer Research Program Transformative Impact Award, grant ID W81XWH-13-2-0093; WDT and SMD), PCFA/Cancer Australia/Movember (grant IDs 1012337 and 1043482; WDT and LAS), Cancer Australia (grant ID 1043497; WDT and JC) and The Ray and Shirl Norman Cancer Research Trust (WDT and LAS). The Dame Roma Mitchell Cancer Research Laboratories were supported by an establishment grant from the PCFA (ID 2011/0452). FO was supported by a PhD project grant from Prostate Cancer UK (S10-10). LAS is supported by a Young Investigator Award from the Prostate Cancer Foundation (the Foundation 14 award)

The activation of OR51E1 causes growth suppression of human prostate cancer cells

The development of prostate cancer (PCa) is regulated by the androgen-dependent activity of the androgen receptor (AR). Androgen-deprivation therapy (ADT) is therefore the gold standard treatment to suppress malignant progression of PCa. Nevertheless, due to the development of castration resistance, recurrence of disease after initial response to ADT is a major obstacle to successful treatment. As G-protein coupled receptors play a fundamental role in PCa physiology, they might represent promising alternative or combinatorial targets for advanced diseases. Here, we verified gene expression of the olfactory receptors (ORs) OR51E1 [prostate-specific G-protein coupled receptor 2 (PSGR2)] and OR51E2 (PSGR) in human PCa tissue by RNA-Seq analysis and RT-PCR and elucidated the subcellular localization of both receptor proteins in human prostate tissue. The OR51E1 agonist nonanoic acid (NA) leads to the phosphorylation of various protein kinases and growth suppression of the PCa cell line LNCaP. Furthermore, treatment with NA causes reduction of androgen-mediated AR target gene expression. Interestingly, NA induces cellular senescence, which coincides with reduced E2F1 mRNA levels. In contrast, treatment with the structurally related compound 1-nonanol or the OR2AG1 agonist amyl butyrate, neither of which activates OR51E1, did not lead to reduced cell growth or an induction of cellular senescence. However, decanoic acid, another OR51E1 agonist, also induces cellular senescence. Thus, our results suggest the involvement of OR51E1 in growth processes of PCa cells and its impact on AR-mediated signaling. These findings provide novel evidences to support the functional importance of ORs in PCa pathogenesis

A reciprocal feedback between the PDZ binding kinase and androgen receptor drives prostate cancer.

Elucidation of mechanisms underlying the increased androgen receptor (AR) activity and subsequent development of aggressive prostate cancer (PrCa) is pivotal in developing new therapies. Using a systems biology approach, we interrogated the AR-regulated proteome and identified PDZ binding kinase (PBK) as a novel AR-regulated protein that regulates full-length AR and AR variants (ARVs) activity in PrCa. PBK overexpression in aggressive PrCa is associated with early biochemical relapse and poor clinical outcome. In addition to its carboxy terminus ligand-binding domain, PBK directly interacts with the amino terminus transactivation domain of the AR to stabilise it thereby leading to increased AR protein expression observed in PrCa. Transcriptome sequencing revealed that PBK is a mediator of global AR signalling with key roles in regulating tumour invasion and metastasis. PBK inhibition decreased growth of PrCa cell lines and clinical specimen cultured ex vivo. We uncovered a novel interplay between AR and PBK that results in increased AR and ARVs expression that executes AR-mediated growth and progression of PrCa, with implications for the development of PBK inhibitors for the treatment of aggressive PrCa