Targeting of CTCF to the nucleolus inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism

Multiple functions have been reported for the transcription factor and candidate tumour suppressor, CTCF. Among others, they include regulation of cell growth, differentiation and apoptosis, enhancer-blocking activity and control of imprinted genes. CTCF is usually localized in the nucleus and its subcellular distribution during the cell cycle is dynamic; CTCF was found associated with mitotic chromosomes and the midbody, suggesting different roles for CTCF at different stages of the cell cycle. Here we report the nucleolar localization of CTCF in several experimental model systems. Translocation of CTCF from nucleoplasm to the nucleolus was observed after differentiation of K562 myeloid cells and induction of apoptosis in MCF7 breast cancer cells. CTCF was also found in the nucleoli in terminally differentiated rat trigeminal ganglion neurons. Thus our data show that nucleolar localization of CTCF is associated with growth arrest. Interestingly, the 180 kDa poly(ADP-ribosyl)ated isoform of CTCF was predominantly found in the nucleoli fractions. By transfecting different CTCF deletion constructs into cell lines of different origin we demonstrate that the central zinc-finger domain of CTCF is the region responsible for nucleolar targeting. Analysis of subnucleolar localization of CTCF revealed that it is distributed homogeneously in both dense fibrillar and granular components of the nucleolus, but is not associated with fibrillar centres. RNA polymerase I transcription and protein synthesis were required to sustain nucleolar localization of CTCF. Notably, the labelling of active transcription sites by in situ run-on assays demonstrated that CTCF inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism

Identification of Androgen Receptor Metabolic Correlome Reveals the Repression of Ceramide Kinase by Androgens

Prostate cancer (PCa) is one of the most prevalent cancers in men. Androgen receptor signaling plays a major role in this disease, and androgen deprivation therapy is a common therapeutic strategy in recurrent disease. Sphingolipid metabolism plays a central role in cell death, survival, and therapy resistance in cancer. Ceramide kinase (CERK) catalyzes the phosphorylation of ceramide to ceramide 1-phosphate, which regulates various cellular functions including cell growth and migration. Here we show that activated androgen receptor (AR) is a repressor of CERK expression. We undertook a bioinformatics strategy using PCa transcriptomics datasets to ascertain the metabolic alterations associated with AR activity. CERK was among the most prominent negatively correlated genes in our analysis. Interestingly, we demonstrated through various experimental approaches that activated AR reduces the mRNA expression of CERK: (i) expression of CERK is predominant in cell lines with low or negative AR activity; (ii) AR agonist and antagonist repress and induce CERK mRNA expression, respectively; (iii) orchiectomy in wildtype mice or mice with PCa (harboring prostate-specific Pten deletion) results in elevated Cerk mRNA levels in prostate tissue. Mechanistically, we found that AR represses CERK through interaction with its regulatory elements and that the transcriptional repressor EZH2 contributes to this process. In summary, we identify a repressive mode of AR that influences the expression of CERK in PCa.A.G.-M. is funded by the MINECO (SAF2016-79695-R) and the department of education (IKERTALDE IT1106-16). V.T. is funded by Fundación Vasca de Innovación e Investigación Sanitarias, BIOEF (BIO15/CA/052), the AECC J.P. Bizkaia and the Basque Department of Health (2016111109) and the MINECO RTI2018-097267-B-I00. The work of A. Carracedo is supported by the Basque Department of Industry, Tourism and Trade (Elkartek), the department of education (IKERTALDE IT1106-16) and health (RIS3), the MICINN (PID2019-108787RB-I00 (FEDER/EU); Severo Ochoa Excellence Accreditation SEV-2016-0644; Excellence Networks RED2018-102769-T), the AECC (GCTRA18006CARR), La Caixa Foundation (ID 100010434), under the agreement LCF/PR/HR17/ and the European Research Council (Consolidator Grant 819242). CIBERONC was co-funded with FEDER funds and funded by ISCIII

PI3K-regulated Glycine N-methyltransferase is required for the development of prostate cancer

[EN] Glycine N-Methyltransferase (GNMT) is a metabolic enzyme that integrates metabolism and epigenetic regulation. The product of GNMT, sarcosine, has been proposed as a prostate cancer biomarker. This enzyme is predominantly expressed in the liver, brain, pancreas, and prostate tissue, where it exhibits distinct regulation. Whereas genetic alterations in GNMT have been associated to prostate cancer risk, its causal contribution to the development of this disease is limited to cell line-based studies and correlative human analyses. Here we integrate human studies, genetic mouse modeling, and cellular systems to characterize the regulation and function of GNMT in prostate cancer. We report that this enzyme is repressed upon activation of the oncogenic Phosphoinositide-3-kinase (PI3K) pathway, which adds complexity to its reported dependency on androgen signaling. Importantly, we demonstrate that expression of GNMT is required for the onset of invasive prostate cancer in a genetic mouse model. Altogether, our results provide further support of the heavy oncogenic signal-dependent regulation of GNMT in prostate cancer.We are grateful to the Carracedo lab for valuable input, to Drs. Ana M. Aransay, James D. Sutherland and F. Elortza for technical advice, and Drs. Michelle Clasquin, Katie Sellers and Katya Marjon at Agios Pharmaceuticals for performing, processing and analyzing the metabolomics experiments. We thank the Basque Biobank for Research (BIOEF) for the support with prostate specimen acquisition and management. A.A-A. was funded by the Basque Government (predoctoral fellowship). V.T. is funded by Fundación Vasca de Innovación e Investigación Sanitarias, BIOEF (BIO15/CA/052), the AECC J.P. Bizkaia, the Basque Department of Health (2016111109) and the MICINN RTI2018-097267-B-I00. I.M. is supported by Fundación Cris Contra el Cáncer (PR_TPD_2020-19). The work of A. Carracedo is supported by the Basque Department of Industry, Tourism and Trade (Elkartek), the department of education (IKERTALDE IT1106-16) and health (RIS3), the BBVA foundation, the MICINN (SAF2016-79381-R; PID2019-108787RB-I00 (FEDER/EU); Severo Ochoa Excellence Accreditation SEV-2016-0644; Excellence Networks RED2018-102769-T), the AECC (GCTRA18006CARR), Vencer el Cáncer Foundation, La Caixa Foundation (ID 100010434), under the agreement LCF/PR/HR17/ and the European Research Council (Starting Grant 336343, PoC 754627, Consolidator Grant 819242). CIBERONC was co-funded with FEDER funds and funded by ISCIII. We are grateful for the support of Mondravember and Movembergara. A.E. was supported by MCIN/AEI/10.13039/501100011033 and the EU programme NextGenerationEU/PRTR (IJC2020-043583-I). The work of JM Mato was supported by NIH grant R01CA172086 and SAF2017-88041-R. EB is funded by the MICINN (BFU2016-76872-R (FEDER/EU), PID2019-108112RB-I00, and Excellence Networks SAF2017-90794-REDT)

Integrative Analysis of Transcriptomics and Clinical Data Uncovers the Tumor- Suppressive Activity of MITF in Prostate Cancer

The dysregulation of gene expression is an enabling hallmark of cancer. Computational analysis of transcriptomics data from human cancer specimens, complemented with exhaustive clinical annotation, provides an opportunity to identify core regulators of the tumorigenic process. Here we exploit well-annotated clinical datasets of prostate cancer for the discovery of transcriptional regulators relevant to prostate cancer. Following this rationale, we identify Microphthalmia-associated transcription factor (MITF) as a prostate tumor suppressor among a subset of transcription factors. Importantly, we further interrogate transcriptomics and clinical data to refine MITF perturbation-based empirical assays and unveil Crystallin Alpha B (CRYAB) as an unprecedented direct target of the transcription factor that is, at least in part, responsible for its tumor-suppressive activity in prostate cancer. This evidence was supported by the enhanced prognostic potential of a signature based on the concomitant alteration of MITF and CRYAB in prostate cancer patients. In sum, our study provides proof-of-concept evidence of the potential of the bioinformatics screen of publicly available cancer patient databases as discovery platforms, and demonstrates that the MITF-CRYAB axis controls prostate cancer biology.The work of V. Torrano is funded by Fundacion Vasca de Innovacion e Investigacion Sanitarias, BIOEF (BIO15/CA/052), the AECC J.P. Bizkaia and the Basque Department of Health (2016111109). The work of A. Carracedo is supported by the Basque Department of Industry, Tourism and Trade (Etortek) and the Department of Education (IKERTALDE IT1106-16, also participated by A. Gomez-Munoz), the BBVA Foundation, the MINECO (SAF2016-79381-R (FEDER/EU); Severo Ochoa Excellence Accreditation SEV-2016-0644; Excellence Networks SAF2016-81975-REDT), European Training Networks Project (H2020-MSCA-ITN-308 2016 721532), the AECC IDEAS16 (IDEAS175CARR) and the European Research Council (Starting Grant 336343, PoC 754627). CIBERONC was co-funded with FEDER funds. The work of M. Graupera is supported by the MINECO (SAF2014-59950-P). The work of A. Aransay is supported by the Basque Department of Industry, Tourism and Trade (Etortek and Elkartek Programs), the Innovation Technology Department of Bizkaia County, CIBERehd Network and Spanish MINECO the Severo Ochoa Excellence Accreditation (SEV-2016-0644). R. Barrio acknowledges Spanish MINECO (BFU2014-52282-P, Consolider BFU2014-57703-REDC), the Departments of Education and Industry of the Basque Government (PI2012/42) and the Bizkaia County. J. Starkova acknowledges the Ministry of Health of Czech Republic AZV NV15-28848A. We are thankful to the Basque Biobank for Research (BIOEF) for the custody and management of human prostate specimens used in this study