Sumoylation delays the ATF7 transcription factor subcellular localization and inhibits its transcriptional activity

Over the past few years, small ubiquitin-like modifier (SUMO) modification has emerged as an important regulator of diverse pathways and activities including protein localization and transcriptional regulation. We identified a consensus sumoylation motif (IKEE), located within the N-terminal activation domain of the ATF7 transcription factor and thus investigated the role of this modification. ATF7 is a ubiquitously expressed transcription factor, homologous to ATF2, that binds to CRE elements within specific promoters. This protein is able to heterodimerize with Jun or Fos proteins and its transcriptional activity is mediated by interaction with TAF12, a subunit of the general transcription factor TFIID. In the present article, we demonstrate that ATF7 is sumoylated in vitro (using RanBP2 as a E3-specific ligase) and in vivo. Moreover, we show that ATF7 sumoylation affects its intranuclear localization by delaying its entry into the nucleus. Furthermore, SUMO conjugation inhibits ATF7 transactivation activity by (i) impairing its association with TAF12 and (ii) blocking its binding-to-specific sequences within target promoters

Epigenetics, a key player of immunotherapy resistance

In 2018, the Nobel Prize in medicine was awarded to James P. Allison and Tasuku Honjo for their work on the description of immune checkpoint inhibitors which contributed to the development of new anti-cancer immunotherapies. However, although these new therapeutic strategies, which are designed to limit immune escape of cancer cells, have been used or tested successfully in many different cancers, a large proportion of patients have been described to resist and not respond to these new treatments. The new incoming challenge is now therefore to overcome these resistance and new recent data presented epigenetic modifications as promising targets to restore anti-tumor immunity. Indeed, both DNA methylation and post-translational histone modifications have been described to regulate immune checkpoint inhibitor expression, tumor-associated antigen presentation or cancer cell editing by the immune system and therefore establishing epigenetic drugs as a potential complement to immunotherapies to improve their efficiency

Interplay between ROS and autophagy in cancer cells, from tumor initiation to cancer therapy

Cancer formation is a complex and highly regulated multi-step process which is highly dependent of its environment, from the tissue to the patient. This complexity implies the development of specific treatments adapted to each type of tumor. The initial step of cancer formation requires the transformation of a healthy cell to a cancer cell, a process regulated by multiple intracellular and extracellular stimuli. The further steps, from the anarchic proliferation of cancer cells to form a primary tumor to the migration of cancer cells to distant organs to form metastasis, are also highly dependent of the tumor environment but of intracellular molecules and pathways as well. In this review, we will focus on the regulatory role of reactive oxygen species (ROS) and autophagy levels during the course of cancer development, from cellular transformation to the formation of metastasis. These data will allow us to discuss the potential of this molecule or pathway as putative future therapeutic targets

Investigating gene expression array with outliers and missing data in bladder cancer

International audienceIn this article, we present a methodology to perform selection among genes based on their expression in various groups of patients, in order to find new genetic markers for specific pathologies. Our approach is based on clustering the denoised data and computing a LASSO (Least Absolute Shrinkage and Selection Operator) estimator, in order to select the relevant genes. This latter belongs to the class of penalized regression estimators where the penalty is a multiple of the ℓ1-norm of the regression vector. Gene markers of the most severe tumor state are finally provided using the proposed approach

Specific or not specific recruitment of DNMTs for DNA methylation, an epigenetic dilemma

Abstract Our current view of DNA methylation processes is strongly moving: First, even if it was generally admitted that DNMT3A and DNMT3B are associated with de novo methylation and DNMT1 is associated with inheritance DNA methylation, these distinctions are now not so clear. Secondly, since one decade, many partners of DNMTs have been involved in both the regulation of DNA methylation activity and DNMT recruitment on DNA. The high diversity of interactions and the combination of these interactions let us to subclass the different DNMT-including complexes. For example, the DNMT3L/DNMT3A complex is mainly related to de novo DNA methylation in embryonic states, whereas the DNMT1/PCNA/UHRF1 complex is required for maintaining global DNA methylation following DNA replication. On the opposite to these unspecific DNA methylation machineries (no preferential DNA sequence), some recently identified DNMT-including complexes are recruited on specific DNA sequences. The coexistence of both types of DNA methylation (un/specific) suggests a close cooperation and an orchestration between these systems to maintain genome and epigenome integrities. Deregulation of these systems can lead to pathologic disorders

Specific regional distribution of gec1 mRNAs in adult rat central nervous system.

International audienceGEC1 protein shares high identity with GABARAP (GABA(A) Receptor-Associated Protein), interacts with tubulin and GABA(A) receptors and is potentially involved in intracellular transport processes. Recently, using quantitative real time PCR, we have reported the gec1 mRNA expression in different rat brain areas. In the present study, we investigated the cell types expressing gec1 in rat brain. Sense and anti-sense gec1 RNA probes, corresponding to the 3'-untranslated region, were generated. In northern blotting experiments, the anti-sense probe revealed only the 1.75 kb gec1 mRNAs. On the other hand, in immunohistochemistry experiments, GEC1 polyclonal antibodies did not discriminate between GEC1 and GABARAP proteins. Therefore, we used digoxigenin-labeled RNA probes for in situ hybridization (ISH) experiments to map the gec1 expression. Using the anti-sense probe, we detected the gec1 mRNAs specifically in neurons throughout the rostrocaudal extent of the brain as well as in the spinal cord. Although a majority of neurons expressed the gec1 mRNAs, different intensities of labeling were observed depending on the areas: the strongest labeling was observed in the isocortex, hippocampus, basal telencephalon, some thalamic and most of hypothalamic nuclei, cerebellum, and numerous brainstem nuclei. Furthermore, the gec1 mRNAs were intensely expressed in neurons involved in somatomotor and neuroendocrine functions and weakly expressed in sensory and reticular structures. These results corroborate the putative role of the GEC1 protein in the trafficking of receptor GABA(A)

Technical controls demonstrating the specificity of P-LISA signals.

<p>(<b>A</b>) MDA-MB-436 cells were cultured for 24 h at 37°C and 5% CO₂. P-LISA were performed according to the manufacturer’s recommendations. No primary antibodies were added before performing P-LISA with PLA R+ (anti-rabbit) and PLA M- (anti-mouse) (left panel); P-LISA SQSTM1/LC3B was also performed with PLA R+ (anti-rabbit) against LC3B and with PLA G- (anti-goat) unable to recognize SQSMT1 (left panel). Similar controls were performed for P-LISA SQSTM1/GL1, P-LISA LC3B/NIX and P-LISA GL1/NIX. (<b>B</b>) Quantification of <i>LC3B</i> mRNA expression in MDA-MB-436 cells following <i>LC3B</i> siRNA transfection analyzed using qRT-PCR (top panel). Quantification of SQSTM1/LC3 interactions detected by P-LISA in MDA-MB-436 cells transfected or not with <i>LC3B</i> siRNA (bottom panel) according to the manufacturer’s recommendations using rabbit anti-LC3B and mouse anti-SQSTM1 antibodies. (<b>C</b>) Absence of SQSTM1/LC3B P-LISA signals in murine cells since the anti-SQSTM1 antibody is specific of the human SQSTM1 protein and restoration of P-LISA signals when these cells were transfected with a vector coding the human HA-SQSTM1 protein. (<b>D</b>) Absence of GL1 protein was validated using western blotting in MDA-MB-436 cells expressing or not a <i>GABARAPL1</i> shRNA (<b>E</b>) Quantification of NIX/GL1 interactions was performed by P-LISA in MDA-MB-436 cells expressing or not a <i>GABARAPL1</i> shRNA using rabbit anti-GL1 and mouse anti-NIX antibodies.</p

Detection of SQSTM1/LC3B, SQSTM1/GL1, NIX/GL1 and NIX/LC3B interactions by P-LISA.

<p>(<b>A</b>) MDA-MB-436 cells were cultured for 24 h at 37°C and 5% CO₂, fixed, permeabilized, blocked with 5% BSA, incubated with rabbit anti-LC3B, rabbit anti-GL1, mouse anti-SQSTM1 or/and mouse anti-NIX antibodies overnight at 4°C and then with an Alexa Fluor 488 goat anti-rabbit and an Alexa Fluor 555 goat anti-mouse, respectively, for 1 h. The cells were then analyzed using a confocal microscope. (<b>B</b>) For P-LISA, the protocol was performed according to the manufacturer’s recommendations using the same antibodies as described above. Nuclei were stained with DAPI. Each picture is representative of a typical cell staining observed in 10 fields chosen at random. Scale bars: 20μm.</p