Aurélie Ladang

The emerging role of lysine acetylation of non-nuclear proteins

Lysine acetylation is a post-translational modification that critically regulates gene transcription by targeting histones as well as a variety of transcription factors in the nucleus. More recent reports have also demonstrated that numerous proteins located outside the nucleus are also acetylated and that this modification has profound consequences on their functions. This review describes the latest findings on the substrates acetylated outside the nucleus and on the acetylases and deacetylates that catalyse these modifications. Protein acetylation is emerging as a major mechanism by which key proteins are regulated in many physiological processes such as migration, metabolism and aging as well as in pathological circumstances such as cancer and neurodegenerative disorders.

NF-κB-induced KIAA1199 promotes survival through EGFR signalling

Constitutive activation of EGFR- and NF-κB-dependent pathways is a hallmark of cancer, yet signalling proteins that connect both oncogenic cascades are poorly characterized. Here we define KIAA1199 as a BCL-3- and p65-dependent gene in transformed keratinocytes. KIAA1199 expression is enhanced on human papillomavirus (HPV) infection and is aberrantly expressed in clinical cases of cervical (pre)neoplastic lesions. Mechanistically, KIAA1199 binds Plexin A2 and protects from Semaphorin 3A-mediated cell death by promoting EGFR stability and signalling. Moreover, KIAA1199 is an EGFR-binding protein and KIAA1199 deficiency impairs EGF-dependent Src, MEK1 and ERK1/2 phosphorylations. Therefore, EGFR stability and signalling to downstream kinases requires KIAA1199. As such, KIAA1199 promotes EGF-mediated epithelial–mesenchymal transition (EMT). Taken together, our data define KIAA1199 as an oncogenic protein induced by HPV infection and constitutive NF-κB activity that transmits pro-survival and invasive signals through EGFR signalling.

DERP6 (ELP5) and C3ORF75 (ELP6) Regulate Tumorigenicity and Migration of Melanoma Cells as Subunits of Elongator

Background: Elongator is an acetylase complex that regulates cell migration. Results: DERP6 (ELP5) and C3ORF75 (ELP6) are characterized as Elongator subunits that control cell motility and tumorigenicity of melanoma cells. ELP5 ensures Elongator integrity by connecting ELP3 to ELP4. Conclusion: ELP5 and ELP6 are new players for migration and tumorigenicity of transformed cells. Significance: Elongator may be involved in both tumor initiation and progression. The Elongator complex is composed of 6 subunits (Elp1-Elp6) and promotes RNAPII transcript elongation through histone acetylation in the nucleus as well as tRNA modification in the cytoplasm. This acetyltransferase complex directly or indirectly regulates numerous biological processes ranging from exocytosis and resistance to heat shock in yeast to cell migration and neuronal differentiation in higher eukaryotes. The identity of human ELP1 through ELP4 has been reported but human ELP5 and ELP6 have remained uncharacterized. Here, we report that DERP6 (ELP5) and C3ORF75 (ELP6) encode these subunits of human Elongator. We further investigated the importance and function of these two subunits by a combination of biochemical analysis and cellular assays. Our results show that DERP6/ELP5 is required for the integrity of Elongator and directly connects ELP3 to ELP4. Importantly, the migration and tumorigenicity of melanoma-derived cells are significantly decreased upon Elongator depletion through ELP1 or ELP3. Strikingly, DERP6/ELP5 and C3ORF75/ELP6-depleted melanoma cells have similar defects, further supporting the idea that DERP6/ELP5 and C3ORF75/ELP6 are essential for Elongator function. Together, our data identify DERP6/ELP5 and C3ORF75/ELP6 as key players for migration, invasion and tumorigenicity of melanoma cells, as integral subunits of Elongator.

Elp3 drives Wnt-dependent tumor initiation and regeneration in the intestine

Tumor initiation in the intestine can rapidly occur from Lgr5+ crypt columnar stem cells. Dclk1 is a marker of differentiated Tuft cells and, when coexpressed with Lgr5, also marks intestinal cancer stem cells. Here, we show that Elp3, the catalytic subunit of the Elongator complex, is required for Wnt-driven intestinal tumor initiation and radiation-induced regeneration by maintaining a subpool of Lgr5+/Dclk1+/Sox9+ cells. Elp3 deficiency dramatically delayed tumor appearance in Apc-mutated intestinal epithelia and greatly prolonged mice survival without affecting the normal epithelium. Specific ablation of Elp3 in Lgr5+ cells resulted in marked reduction of polyp formation upon Apc inactivation, in part due to a decreased number of Lgr5+/Dclk1+/Sox9+ cells. Mechanistically, Elp3 is induced by Wnt signaling and promotes Sox9 translation, which is needed to maintain the subpool of Lgr5+/Dclk1+ cancer stem cells. Consequently, Elp3 or Sox9 depletion led to similar defects in Dclk1+ cancer stem cells in ex vivo organoids. Finally, Elp3 deficiency strongly impaired radiation-induced intestinal regeneration, in part because of decreased Sox9 protein levels. Together, our data demonstrate the crucial role of Elp3 in maintaining a subpopulation of Lgr5-derived and Sox9-expressing cells needed to trigger Wnt-driven tumor initiation in the intestine.

The Prosurvival IKK-Related Kinase IKKε Integrates LPS and IL17A Signaling Cascades to Promote Wnt-Dependent Tumor Development in the Intestine

Constitutive Wnt signaling promotes intestinal cell proliferation, but signals from the tumor microenvironment are also required to support cancer development. The role that signaling proteins play to establish a tumor microenvironment has not been extensively studied. Therefore, we assessed the role of the proinflammatory Ikk-related kinase Ikkε in Wnt-driven tumor development. We found that Ikkε was activated in intestinal tumors forming upon loss of the tumor suppressor Apc Genetic ablation of Ikkε in β-catenin-driven models of intestinal cancer reduced tumor incidence and consequently extended survival. Mechanistically, we attributed the tumor-promoting effects of Ikkε to limited TNF-dependent apoptosis in transformed intestinal epithelial cells. In addition, Ikkε was also required for lipopolysaccharide (LPS) and IL17A-induced activation of Akt, Mek1/2, Erk1/2, and Msk1. Accordingly, genes encoding pro-inflammatory cytokines, chemokines, and anti-microbial peptides were downregulated in Ikkε-deficient tissues, subsequently affecting the recruitment of tumor-associated macrophages and IL17A synthesis. Further studies revealed that IL17A synergized with commensal bacteria to trigger Ikkε phosphorylation in transformed intestinal epithelial cells, establishing a positive feedback loop to support tumor development. Therefore, TNF, LPS, and IL17A-dependent signaling pathways converge on Ikkε to promote cell survival and to establish an inflammatory tumor microenvironment in the intestine upon constitutive Wnt activation. Cancer Res; 76(9); 2587-99. ©2016 AACR.

Correction: Elp3 drives Wnt-dependent tumor initiation and regeneration in the intestine

Correction: Elp3 drives Wnt-dependent tumor initiation and regeneration in the intestine Aurélie Ladang, Francesca Rapino, Lukas C. Heukamp, Lars Tharun, Kateryna Shostak, Damien Hermand, Sylvain Delaunay, Iva Klevernic, Zheshen Jiang, Nicolas Jacques, Diane Jamart, Valérie Migeot, Alexandra Florin, Serkan Göktuna, Brigitte Malgrange, Owen J. Sansom, Laurent Nguyen, Reinhard Büttner, Pierre Close, and Alain Chariot Vol. 212, No. 12, November 16, 2015. Pages 2057–2075.