Transcriptional regulation of amino acid metabolism by KDM2B, in the context of ncPRC1.1 and in concert with MYC and ATF4

INTRODUCTION

KDM2B encodes a JmjC domain-containing histone lysine demethylase, which functions as an oncogene in several types of tumors, including TNBC. This study was initiated to address the cancer relevance of the results of our earlier work, which had shown that overexpression of KDM2B renders mouse embryonic fibroblasts (MEFs) resistant to oxidative stress by regulating antioxidant mechanisms.

METHODS

We mainly employed a multi-omics strategy consisting of RNA-Seq, quantitative TMT proteomics, Mass-spectrometry-based global metabolomics, ATAC-Seq and ChIP-seq, to explore the role of KDM2B in the resistance to oxidative stress and intermediary metabolism. These data and data from existing patient datasets were analyzed using bioinformatic tools, including exon-intron-split analysis (EISA), FLUFF and clustering analyses. The main genetic strategy we employed was gene silencing with shRNAs. ROS were measured by flow cytometry, following staining with CellROX and various metabolites were measured with biochemical assays, using commercially available kits. Gene expression was monitored with qRT-PCR and immunoblotting, as indicated.

RESULTS

The knockdown of KDM2B in basal-like breast cancer cell lines lowers the levels of GSH and sensitizes the cells to ROS inducers, GSH targeting molecules, and DUB inhibitors. To address the mechanism of GSH regulation, we knocked down KDM2B in MDA-MB-231 cells and we examined the effects of the knockdown, using a multi-omics strategy. The results showed that KDM2B, functioning in the context of ncPRC1.1, regulates a network of epigenetic and transcription factors, which control a host of metabolic enzymes, including those involved in the SGOC, glutamate, and GSH metabolism. They also showed that KDM2B enhances the chromatin accessibility and expression of MYC and ATF4, and that it binds in concert with MYC and ATF4, the promoters of a large number of transcriptionally active genes, including many, encoding metabolic enzymes. Additionally, MYC and ATF4 binding sites were enriched in genes whose accessibility depends on KDM2B, and analysis of a cohort of TNBCs expressing high or low levels of KDM2B, but similar levels of MYC and ATF4 identified a subset of MYC targets, whose expression correlates with the expression of KDM2B. Further analyses of basal-like TNBCs in the same cohort, revealed that tumors expressing high levels of all three regulators exhibit a distinct metabolic signature that carries a poor prognosis.

CONCLUSIONS

The present study links KDM2B, ATF4, and MYC in a transcriptional network that regulates the expression of multiple metabolic enzymes, including those that control the interconnected SGOC, glutamate, and GSH metabolic pathways. The co-occupancy of the promoters of many transcriptionally active genes, by all three factors, the enrichment of MYC binding sites in genes whose chromatin accessibility depends on KDM2B, and the correlation of the levels of KDM2B with the expression of a subset of MYC target genes in tumors that express similar levels of MYC, suggest that KDM2B regulates both the expression and the transcriptional activity of MYC. Importantly, the concerted expression of all three factors also defines a distinct metabolic subset of TNBCs with poor prognosis. Overall, this study identifies novel mechanisms of SGOC regulation, suggests novel KDM2B-dependent metabolic vulnerabilities in TNBC, and provides new insights into the role of KDM2B in the epigenetic regulation of transcription.

Transcriptional regulation of amino acid metabolism by KDM2B, in the context of ncPRC1.1 and in concert with MYC and ATF4

Introduction

KDM2B encodes a JmjC domain-containing histone lysine demethylase, which functions as an oncogene in several types of tumors, including TNBC. This study was initiated to address the cancer relevance of the results of our earlier work, which had shown that overexpression of KDM2B renders mouse embryonic fibroblasts (MEFs) resistant to oxidative stress by regulating antioxidant mechanisms.

Methods

We mainly employed a multi-omics strategy consisting of RNA-Seq, quantitative TMT proteomics, Mass-spectrometry-based global metabolomics, ATAC-Seq and ChIP-seq, to explore the role of KDM2B in the resistance to oxidative stress and intermediary metabolism. These data and data from existing patient datasets were analyzed using bioinformatic tools, including exon-intron-split analysis (EISA), FLUFF and clustering analyses. The main genetic strategy we employed was gene silencing with shRNAs. ROS were measured by flow cytometry, following staining with CellROX and various metabolites were measured with biochemical assays, using commercially available kits. Gene expression was monitored with qRT-PCR and immunoblotting, as indicated.

Results

The knockdown of KDM2B in basal-like breast cancer cell lines lowers the levels of GSH and sensitizes the cells to ROS inducers, GSH targeting molecules, and DUB inhibitors. To address the mechanism of GSH regulation, we knocked down KDM2B in MDA-MB-231 cells and we examined the effects of the knockdown, using a multi-omics strategy. The results showed that KDM2B, functioning in the context of ncPRC1.1, regulates a network of epigenetic and transcription factors, which control a host of metabolic enzymes, including those involved in the SGOC, glutamate, and GSH metabolism. They also showed that KDM2B enhances the chromatin accessibility and expression of MYC and ATF4, and that it binds in concert with MYC and ATF4, the promoters of a large number of transcriptionally active genes, including many, encoding metabolic enzymes. Additionally, MYC and ATF4 binding sites were enriched in genes whose accessibility depends on KDM2B, and analysis of a cohort of TNBCs expressing high or low levels of KDM2B, but similar levels of MYC and ATF4 identified a subset of MYC targets, whose expression correlates with the expression of KDM2B. Further analyses of basal-like TNBCs in the same cohort, revealed that tumors expressing high levels of all three regulators exhibit a distinct metabolic signature that carries a poor prognosis.

Conclusions

The present study links KDM2B, ATF4, and MYC in a transcriptional network that regulates the expression of multiple metabolic enzymes, including those that control the interconnected SGOC, glutamate, and GSH metabolic pathways. The co-occupancy of the promoters of many transcriptionally active genes, by all three factors, the enrichment of MYC binding sites in genes whose chromatin accessibility depends on KDM2B, and the correlation of the levels of KDM2B with the expression of a subset of MYC target genes in tumors that express similar levels of MYC, suggest that KDM2B regulates both the expression and the transcriptional activity of MYC. Importantly, the concerted expression of all three factors also defines a distinct metabolic subset of TNBCs with poor prognosis. Overall, this study identifies novel mechanisms of SGOC regulation, suggests novel KDM2B-dependent metabolic vulnerabilities in TNBC, and provides new insights into the role of KDM2B in the epigenetic regulation of transcription.

Abstract 6038: KDM2B regulates Serine-Glycine-One Carbon (SGOC) metabolism by targeting the SGOC enzyme genes via a combination of direct and indirect epigenetic mechanisms

Our earlier studies had shown that overexpression of the JmjC domain histone demethylase KDM2B renders mouse embryo fibroblasts (MEFs) resistant to oxidative stress due to the role of KDM2B in the regulation of antioxidant mechanisms. Here we present evidence that the knockdown of KDM2B in basal-like breast cancer cell lines results in a decrease of Glutathione (GSH) levels, a secondary increase of intracellular ROS levels and in enhanced sensitivity to deubiquitinase inhibitors. The expression of the Glutamate-Cystine antiporter, the Glutamate-Cysteine Ligase GCLC/GCLM and the Glutathione Peroxidase GPX4, all of which regulate GSH abundance was not affected. To address the mechanism of the GSH regulation we carried out RNA-Seq, quantitative proteomics and metabolomics analyses in shKDM2B- and empty vector-transduced MDA-MB-231 cells. The results showed that the KD of KDM2B causes major shifts in metabolism and that one of the metabolic pathways whose activity depends on KDM2B is the SGOC pathway, which has a major role in GSH biosynthesis. Experiments in cultured cells confirmed the importance of KDM2B in the regulation of this pathway and they also showed that the inhibition of the pathway via the KD of KDM2B is partly responsible for the shKDM2B-induced inhibition of cell proliferation in culture and in xenograft experiments in NSG mice. More important, the transcriptomic signature of the SGOC pathway correlates with the expression of KDM2B in basal like mammary adenocarcinomas in the TCGA database. The genes encoding the majority of the enzymes in the SGOC pathway are known to be regulated by MYC and ATF4 and our data show that both MYC and ATF4 are under the regulatory control of KDM2B. ATAC-Seq and ChIP-Seq experiments in shKDM2B and control MDA-MB-231 cells also showed that KDM2B binds the promoter region of not only MYC and ATF4, but also of the genes encoding the SGOC enzymes and that it regulates chromatin accessibility and the abundance of H3K4me3/H3K27Ac active histone marks in these promoters. Overall, our data indicate that KDM2B regulates the SGOC pathway by targeting MYC and ATF4 and by making the promoters of the genes encoding the SGOC enzymes accessible to these regulators. Overall, our data provide new evidence on SGOC regulation, and identify novel KDM2B-dependent metabolic vulnerabilities in basal like breast cancer.

Citation Format: Evangelia Chavdoula, Vollter Anastas, Allesandro La Ferlita, Julian Aldana, Giuseppe Carota, Mariarita Spampinato, Sameer Parashar, Ilaria Cosentini, Burak Soysal, Giovanni Nigita, Michael Freitas, Philip Tsichlis. KDM2B regulates Serine-Glycine-One Carbon (SGOC) metabolism by targeting the SGOC enzyme genes via a combination of direct and indirect epigenetic mechanisms. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6038.

Abstract 3019: The epigenetic factor KDM2B alters the serine-glycine synthesis pathway and the one-carbon metabolism (SGOC) in triple-negative breast cancer

Epigenetic and metabolic alterations in cancer cells are intertwined. The concentration of metabolites can influence the activity of chromatin modifiers, which in turn can act as metabolic sensors that translate changes in cellular metabolism to transcriptional reprogramming. In the present study, we investigated the role of histone demethylase KDM2B in the metabolic reprogramming of the triple-negative breast cancer (TNBC), in which KDM2B is selectively expressed at high levels. Knockdown of KDM2B in TNBC cell lines reduced their proliferation rate and tumor growth in vivo. Transcriptomic, proteomic, and metabolomic profiling demonstrated that the Serine-Glycine pathway and One Carbon metabolism (SGOC) and other amino acid biosynthetic and catabolic processes are downregulated by the knockdown of KDM2B. Additionally, we see reduction of metabolites produced via these pathways (purines, pyrimidines, formate, glutathione and NADPH). Importantly, the expression of the enzymes involved in the SGOC metabolic pathway (e.g. PHGDH, PSAT1, PSPH, SHMT2, MTHFD1L, MTHFD2 and DHFR) depends on c-MYC, NRF2, and ATF4 which our data show that they are under the positive regulatory control of KDM2B. The epistatic relationship between these factors, with the expression of the enzymes of the SGOC pathway and the effects of the KDM2B knockdown on chromatin occupancy and accessibility of the promoters of these factors is in progress and will be presented. Analysis of TCGA data showed positive and statistically significant correlations between KDM2B and the SGOC gene signature in TNBC patients. In addition, the metabolic pathway signature that distinguishes control and shKDM2B-transduced cells corresponds to the metabolic signature of a subset of TNBCs, which have been reported to carry poor prognosis. The present study highlights the role of the epigenetic factor KDM2B as an upstream regulator of the metabolic reprogramming of TNBC.

Citation Format: Evangelia Chavdoula, Vollter Anastas, Alessandro La Ferlita, Julian Aldana, Anuvrat Sircar, Michael A. Freitas, Lalit Sehgal, Philip N. Tsichlis. The epigenetic factor KDM2B alters the serine-glycine synthesis pathway and the one-carbon metabolism (SGOC) in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3019.

miR-181c regulates MCL1 and cell survival in GATA2 deficient cells

GATA2 is a transcription factor critical for hematopoiesis. Germline mutations in GATA binding protein 2 (GATA2) led to haploinsufficiency, severe cytopenias of multiple cell lineages, susceptibility to infections and strong propensity to develop myelodysplastic syndrome, and acute myeloid leukemia. Mechanisms of progressive cytopenias remain unclear. MicroRNA (miRNA) represents a unique mechanism of post-transcriptional gene regulation. In this study, miRNA profiles were evaluated and eight miRNAs were found to be differentially expressed (≥2-fold, P ≤ 0.05) in patient-derived cell lines (N = 13) in comparison to controls (N = 10). miR-9, miR-181a-2-3p, miR-181c, miR-181c-3p, miR-486-3p, and miR-582 showed increased expression, whereas miR-223 and miR-424-3p showed decreased expression. Cell death assays indicated that miR-181c potently induces cell death in lymphoid (Ly-8 and SP-53) and myeloid (HL-60) cell lines. miR-181c was predicted to target myeloid cell leukemia (MCL)1, which was confirmed by transfection assays, resulting in significantly reduced MCL1 mRNA and decreased live cell numbers. Bone marrow analysis of 34 GATA2 patients showed significantly decreased cellularity, CD34-positive cells, monocytes, dendritic cells, NK cells, B cells, and B cell precursors in comparison to healthy controls (N = 29; P < 0.001 for each), which was accompanied by decreased levels of MCL1 (P < 0.05). GATA2 expression led to significant repression of miR-181c expression in transfection experiments. Conversely, knockdown of GATA2 led to increased miR-181c expression. These findings indicate that miR-181c expression is increased and MCL1 levels decreased in GATA2 deficiency cells, and that GATA2 represses miR-181c transcription. Increased miR-181c may contribute to elevated cell death and cytopenia in GATA2 deficiency potentially through down-regulation of MCL1.

AKT3-mediated IWS1 phosphorylation promotes the proliferation of EGFR-mutant lung adenocarcinomas through cell cycle-regulated U2AF2 RNA splicing

AKT-phosphorylated IWS1 regulates alternative RNA splicing via a pathway that is active in lung cancer. RNA-seq studies in lung adenocarcinoma cells lacking phosphorylated IWS1, identified a exon 2-deficient U2AF2 splice variant. Here, we show that exon 2 inclusion in the U2AF2 mRNA is a cell cycle-dependent process that is regulated by LEDGF/SRSF1 splicing complexes, whose assembly is controlled by the IWS1 phosphorylation-dependent deposition of histone H3K36me3 marks in the body of target genes. The exon 2-deficient U2AF2 mRNA encodes a Serine-Arginine-Rich (RS) domain-deficient U2AF65, which is defective in CDCA5 pre-mRNA processing. This results in downregulation of the CDCA5-encoded protein Sororin, a phosphorylation target and regulator of ERK, G2/M arrest and impaired cell proliferation and tumor growth. Analysis of human lung adenocarcinomas, confirmed activation of the pathway in EGFR-mutant tumors and showed that pathway activity correlates with tumor stage, histologic grade, metastasis, relapse after treatment, and poor prognosis.

Abstract PO010: The inhibition of IWS1 phosphorylation promotes genomic instability, the cGAS/STING pathway activation and PD-L1 levels, through the U2AF2 alternative RNA splicing and Sororin expression

We have previously shown that the loss of IWS1 phosphorylation promotes the alternative RNA splicing of U2 Associated-Factor 2 (U2AF2), resulting in transcripts lacking exon 2 in lung adenocarcinoma cells. This exon encodes part of the U2AF65 Serine-Rich (SR) Domain, which is required for its binding with pre-mRNA Processing factor 19 (Prp19). We have also shown that inhibition of the pathway results in the downregulation of cell cycle division associated 5 (CDCA5), and its protein product Sororin, a phosphorylation target and regulator of ERK and member of the cohesin complex, leading to G2/M phase arrest, sister-chromatid cohesion defects, impaired cell proliferation and tumor growth in mouse xenografts models. Here, we show that the loss of IWS1 results in genomic instability and accumulation of cytosolic dsDNA, an effect rescued by the expression of Sororin. The dsDNA is censored by cyclic GMP-AMP synthetase (cGAS), activating the STING/TBK1 pathway. The latter leads to increased expression of Interferon Regulatory Factor-3 (IRF-3) targets along with PD-L1. More importantly, IWS1 phosphorylation, U2AF2 RNA splicing pattern and Sororin expression negatively correlate with the cGAS/STING pathway and PD-L1 expression in lung adenocarcinoma patients. These results highlight the role of IWS1 phosphorylation-dependent RNA splicing in governing genomic stability, and proposes this axis as a novel drug target for a synergy with PD-L1/PD-1 blockade in lung adenocarcinoma patients.

Citation Format: Georgios I. Laliotis, Evangelia Chavdoula, Abdul Kaba, Alessandro La Ferlita, Vollter Anastas, Arturo Orlacchio, Lalit Sehgal, David P. Carbone, Vincenzo Coppola, Philip N. Tsichlis. The inhibition of IWS1 phosphorylation promotes genomic instability, the cGAS/STING pathway activation and PD-L1 levels, through the U2AF2 alternative RNA splicing and Sororin expression [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO010.

Abstract PO088: Sensitivity of cancer cells to oncolytic viruses is defined by IWS1 phosphorylation dependent epigenetic regulation of U2AF2 splicing and nucleocytoplasmic export of type I IFN transcripts

We have previously shown that loss of IWS1 phosphorylation promotes the alternative RNA splicing of U2 Associated-Factor 2 (U2AF2), resulting in transcripts lacking exon 2. This exon encodes part of the Serine-Rich (SR) domain of U2AF65, which is responsible for its binding with pre-mRNA Processing Factor 19 (Prp19). Here, we show that whereas both U2AF65 isoforms bind cytoplasmic accumulation response elements (CAR-E) of intronless mRNAs, the loading of Prp19 occurs only in exon 2-containing U2AF65, in cells expressing phosphorylated IWS1, promoting their nucleocytoplasmic export. Furthermore, this Prp19 loading is RNA Pol II dependent. Given that IFNA1 and IFNB1 are among the target genes, the expression of IFNα and IFNβ was decreased in cells deficient in IWS1 phosphorylation, and their sensitivity to the oncolytic VSV and Reovirus virus infection was increased accordingly. More importantly, treatment of the lung adenocarcinoma cells with the pan-AKT inhibitor, MK2206 phenocopied the loss of IWS1 phosphorylation and showed increased sensitivity to oncolytic viral infection. These data identify a novel mechanism by which the AKT/p-IWS1 axis, via the epigenetic regulation of alternative RNA splicing, contribute to the sensitivity to oncolytic viruses.

Citation Format: Georgios I. Laliotis, Adam D. Kenney, Evangelia Chavdoula, Arturo Orlacchio, Vollter Anastas, Alessandro La Ferlita, Abdul Kaba, Lalit Sehgal, Vincenzo Coppola, Jacob S. Yount, Philip N. Tsichlis. Sensitivity of cancer cells to oncolytic viruses is defined by IWS1 phosphorylation dependent epigenetic regulation of U2AF2 splicing and nucleocytoplasmic export of type I IFN transcripts [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO088.

Abstract PO-011: IWS1 phosphorylation promotes tumor growth and predicts poor prognosis in EGFR mutant lung adenocarcinoma patients, through the epigenetic regulation of U2AF2 RNA splicing

Our previous studies have shown that IWS1 (Interacts with Spt6) is a phosphorylation target of AKT and regulates the alternative RNA splicing of FGFR2, linking IWS1 with human Non-Small Cell Lung Cancer. To further address the role of IWS1 in alternative RNA splicing in lung cancer, we performed an RNA-seq study using lung adenocarcinoma cells in which IWS1 was knocked down or replaced by its phosphorylation site mutant. The results identified a novel, exon 2 deficient splice variant of the splicing factor U2 Associated-Factor 2 (U2AF2), whose abundance increases, upon the loss of phosphorylated IWS1. This exon encodes part of the U2AF65 Serine-Rich (SR) Domain, which is required for its binding with pre-mRNA Processing factor 19 (Prp19). Here, we show that U2AF2 exon 2 inclusion depends on phosphorylated IWS1, by promoting histone H3K36 trimethylation and the assembly of LEDGF/SRSF1 splicing complexes, in a cell-cycle specific manner. Inhibition of the pathway results in the downregulation of cell cycle division associated 5 (CDCA5), and its protein product, Sororin, a phosphorylation target of ERK and member of the cohesin complex, essential of G2/M phase progression. We also reveal the existence of a novel Sororin/ERK feedback loop controlled by the epigenetic regulation of U2AF2 RNA splicing, downstream of IWS1 phosphorylation. Given that the U2AF2 RNA splicing is regulated through the cell cycle and controls Sororin, our data unravel a novel RNA splicing pattern which is regulated through the cell cycle and feedbacks towards its regulation. Impairment of this signaling pathway leads to leading to G2/M phase arrest, impaired cell proliferation and tumor growth in mouse xenografts models, an effect more pronounced in EGFR mutant cells. Analysis of lung adenocarcinoma samples revealed strong correlations between IWS1 phosphorylation, U2AF2 RNA splicing, and Sororin/p-ERK levels, especially in EGFR, as opposed to K-RAS mutant patients. More importantly, IWS1 phosphorylation and U2AF2 RNA splicing pattern are positively correlated with tumor stage, grade and metastasis, and associated with poor survival in the same patients. This work highlights the instrumental role of the AKT/p-IWS1 axis to alternative RNA splicing in governing cell cycle progression and tumorigenesis and proposes this axis as a novel drug target in EGFR mutant lung adenocarcinoma, by concomitantly affecting the epigenetic regulation of RNA processing and oncogenic signals.

Citation Format: Georgios I. Laliotis, Evangelia Chavdoula, Maria D. Paraskevopoulou, Abdul Kaba, Alessandro La Ferlita, Vollter Anastas, Arturo Orlacchio, Vasiliki Taraslia, Ioannis Vlachos, Marina Capece, Artemis Hatzigeorgiou, Dario Palmieri, Salvatore Alaimo, Christos Tsatsanis, Lalit Sehgal, David P. Carbone, Vincenzo Coppola, Philip N. Tsichlis. IWS1 phosphorylation promotes tumor growth and predicts poor prognosis in EGFR mutant lung adenocarcinoma patients, through the epigenetic regulation of U2AF2 RNA splicing [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PO-011.

Abstract 3649: Alternative RNA splicing of U2AF2, induced by AKT3-phosphorylated IWS1, promotes tumor growth, by activating a CDCA5-pERK positive feedback loop

A phosphoproteomics study of isogenic cell lines expressing the 3 different Akt isoforms identified 606 proteins that are phosphorylated by at least one isoform. About 30 of these proteins were involved in various steps of RNA processing. One of them, IWS1, is a transcription elongation factor, which was originally identified in the yeast Saccharomyces cerevisiae, as a protein that interacts with the histone H3/H4 chaperone Spt6 or as a suppressor of TATA binding protein (TBP) mutations that impair post-recruitment transcriptional activation. The human IWS1 is an 819aa protein, which contains a C-terminal domain that is similar to domain I of the transcription elongation factor TFIIS, and to related domains in Elongin A and the Mediator Complex subunit 26 (Med26). IWS1 was shown to be phosphorylated, primarily by Akt3, at two neighboring sites (Ser720/Thr721). To address the role of phosphorylated IWS1 in RNA processing, we performed an RNA-seq study, using human lung adenocarcinoma cell lines in which IWS1 was knocked down or replaced by its phosphorylation site mutant. This identified the splicing factor U2AF2 as a target of IWS1 phosphorylation. Specifically, phosphorylated IWS1 regulated the alternative splicing of U2AF2 and its loss resulted in U2AF2 transcripts lacking exon 2. This exon encodes part of the U2AF2 Serine-Rich (SR) Domain, required for the binding of U2AF2 with Prp19. Exploring the mechanism of this alternative splicing event revealed that the loss of phosphorylated IWS1 interferes with the recruitment of the histone H3K36 trimethyltransferase SETD2 to an Spt6/IWS1/Aly complex, which assembles on the Ser-2-phosphorylated CTD of RNA-Pol II. The absence of SETD2 recruitment to this complex impairs histone H3K36 trimethylation and the assembly of LEDGF/SRSF1 splicing complexes inthe U2AF2 gene, resulting in the exclusion of exon 2 from the mature U2AF2 mRNA transcript. The loss of the U2AF2/Prp19 interaction results in the downregulation of CDCA5, a component of the cohesin complex, giving rise to genomic instability. Phosphorylation of CDCA5 by p-ERK at Ser79 and Ser209 has a major impact in the regulation of cell proliferation and cancer stem cell renewal, although does not affect its role in the cohesin complex. The effect of phosphorylated CDCA5 on cell proliferation appears to depend on the transcriptional regulation of a set of genes involved in the control of the G2/M phase of the cell cycle, including Cyclin B1 and CDK1. Overall, these data describe a novel pathway, which starts with the phosphorylation of IWS1 by AKT3 and results in the epigenetic modulation of RNA splicing and cell cycle regulation. The importance of this pathway to human cancer was confirmed by meta-analysis of pre-existing patient data, tumor xenograft models and prospective studies on human lung adenocarcinomas.

Citation Format: Georgios I. Laliotis, Evangelia Chavdoula, Maria D. Paraskevopoulou, Vollter Anastas, Ioannis Vlachos, Vasiliki Tarasslia, Artemis Hatzigeorgiou, Dario Palmieri, Abdul Kaba, Marina Capece, Arturo Orlacchio, Lalit Sehgal, Vincenzo Coppola, Philip N. Tsichlis. Alternative RNA splicing of U2AF2, induced by AKT3-phosphorylated IWS1, promotes tumor growth, by activating a CDCA5-pERK positive feedback loop [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3649.