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Ubiquitination is a post-translational modification that plays important roles in various signaling pathways and is notably involved in the coordination of chromatin function and DNA-associated processes. This modification involves a sequential action of several enzymes including E1 ubiquitin-activating, E2 ubiquitin-conjugating and E3 ubiquitin-ligase and is reversed by deubiquitinases (DUBs). Ubiquitination induces degradation of proteins or alteration of protein function including modulation of enzymatic activity, protein-protein interaction and subcellular localization. A critical step in demonstrating protein ubiquitination or deubiquitination is to perform in vitro reactions with purified components. Effective ubiquitination and deubiquitination reactions could be greatly impacted by the different components used, enzyme co-factors, buffer conditions, and the nature of the substrate. Here, we provide step-by-step protocols for conducting ubiquitination and deubiquitination reactions. We illustrate these reactions using minimal components of the mouse Polycomb Repressive Complex 1 (PRC1), BMI1, and RING1B, an E3 ubiquitin ligase that monoubiquitinates histone H2A on lysine 119. Deubiquitination of nucleosomal H2A is performed using a minimal Polycomb Repressive Deubiquitinase (PR-DUB) complex formed by the human deubiquitinase BAP1 and the DEUBiquitinase ADaptor (DEUBAD) domain of its co-factor ASXL2. These ubiquitination/deubiquitination assays can be conducted in the context of either recombinant nucleosomes reconstituted with bacteria-purified proteins or native nucleosomes purified from mammalian cells. We highlight the intricacies that can have a significant impact on these reactions and we propose that the general principles of these protocols can be swiftly adapted to other E3 ubiquitin ligases and deubiquitinases.

Background: Basal cell carcinoma (BCC) is the commonest skin cancer in human. It is characterized by a strictly local malignity with a frequent tendency to relapse. BCC development results from the interaction between environmental factors and genetic alterations, including mutations in the TP53 gene involved in its progression and relapse. TP53 gene is named “guardian of the genome”, as it plays major roles in genomic stability. In addition to mutations, several polymorphisms had been detected in the wild-type TP53. The polymorphic variant is usually associated to BCC diseases at codon 72 of TP53 (Arg72Pro). Objectives: In the present study, we undertook a case control study to explore a possible association between TP53 Arg72Pro polymorphism and the predisposition to BCC in Northwest Algerian population. Methods: TP53 Arg72Pro polymorphism was investigated by PCR/RFLP then confirmed by DNA sequencing of 61 controls versus 50 BCC cases. Results: This study allows us to characterize BCC subgroups regarding age, tumor location, and relapse. No correlation was found between any of these criteria and each of the two variants of TP53 Arg72Pro. No association was found between TP53 Arg72Pro variants and developing BCC either (BCC group: Pro = 54%, versus Control group: Pro = 53 %, P > 0.05, OR 1.52 (0.89 - 2.60)). Finally, as expected, sun-exposure was confirmed as a risk factor for BCC. Conclusions: This study supports that analyzing TP53 Arg72Pro polymorphism is of no interest for identifying high-risk subjects for BCC in the Algerian population. Further studies are needed to explain the role of this polymorphism in genetic predisposition to BCC in some other populations.

The tumor suppressor gene TP53 and its regulator MDM2 are both key players involved in multiple pathways including apoptosis, cellular transcriptional control and cell cycle regulation. Common germline polymorphisms in these genes may affect colorectal cancer (CRC) susceptibility. An arginine-to-proline substitution at codon 72 in the TP53 gene is reported to decrease apoptotic potential, while a thymine-to-guanine polymorphism at nucleotide 309 (named SNP309) of murine double minute 2 MDM2 gene increases its transcription. These two polymorphisms therefore may be of importance in colorectal carcinogenesis. The relation of these polymorphisms to colorectal cancer in the Algerian population was addressed in this study. DNA samples from 121 controls and 116 cases were genotyped for these two polymorphisms by PCR/RFLP then confirmed by sequencing. Unexpectedly no significant association was found between this potential marker TP53 Arg72Pro and CRC (p > 0.05). However, our findings reveal that individuals with the MDM2 SNP309 GG genotype have a low risk of CRC as compared to the TT genotype (OR = 0.49; 95 % CI: 0.24–0.98, p = 0.04), with more significance for females (OR = 0.16; 95 % CI: 0.06–0.41, p

Une mutation des deux allèles du gène Rb durant le développement rétinien norma est responsable de l’apparition du rétinoblastome. La recherche de mutations au niveau du gène Rb reste difficile, car la majorité des altérations sont uniques et dispersées tout au long du gène. Nous rapportons dans notre étude le résultat de l’analyse du gène Rb au niveau constitutionnel et tumoral dans la population algérienne.Notre étude a porté sur un échantillon de 21 patients atteints de rétinoblastome. Le promoteur et les 27 exons avec leurs séquences introniques flanquantes composant le gène Rb ont été amplifiés et analysés par HPLC (chromatographie liquide à haute performance) suivie d’un séquençage. Les variations de bases identifiées au niveau constitutionnel et tumoral sont au nombre de 7 dont 3 mutations non sens, une mutation affectant le site d’épissage, une délétion et 2 polymorphismes. L’analyse du gène Rb a été réalisée chez des enfants atteints de rétinoblastome ne présentant aucun antécédent familial de la maladie. Par cette étude, nous avons pu identifier deux cas sur les 21 étudiés ayant un rétinoblastome pouvant être transmissible.Deux mutations rapportées n’ont jamais été décrites dans la littérature.

Introduction - Le gène TP53 a fait l’objet de très nombreux travaux. Sa nature polymorphe et son rôle central dans la régulation du cycle cellulaire ont mis en évidence son potentiel de gène candidat dans la susceptibilité et la survenue de différents cancers. Bien que plusieurs polymorphismes du gène TP53 aient été étudiés comme facteurs de risque pour différents cancers, le plus largement étudié est le polymorphisme Arg72Pro (rs1042522), à l’origine d’une substitution d’une Arginie (Arg) en Proline (Pro) ou inversement, connu pour ses différentes fonctions biologiques.Notre objectif est d’explorer la participation du polymorphisme (SNP) Arg72Pro du gène TP53, dans l’expressivité du cancer colorectal (CCR) et du carcinome basocellulaire (CBC) dans une population de l’Ouest Algérien.Matériels et Méthodes - Le déséquilibre de transmission allélique de ce SNP a été réalisé sur une population constituée de 116 individus atteints de CCR, 50 sujets atteints de CBC et enfin une population contrôle constituée de 121 individus sains,par la technique de Biologie Moléculaire PCR/RFLP (Polymerase Chain Reaction/Restriction Fragment LengthPolymorphism).Résultats - L’association du marqueur Arg72Pro avec le CBC a montré une augmentation significative de l’allèle Pro chez les cas par rapport aux contrôles (54% vs 46%, OR=8,85 [4,98-16,03], p0.05).Conclusion - Le polymorphisme Arg72Pro du gène TP53 peut être considéré comme marqueur de risque pour le CBC mais pas pour le CCR.

This work provides a comprehensive CpG methylation landscape of the different layers of the human eye that unveils the gene networks associated with their biological functions and how these are disrupted in common visual disorders. Herein, we firstly determined the role of CpG methylation in the regulation of ocular tissue-specification and described hypermethylation of retinal transcription factors (i.e., PAX6, RAX, SIX6) in a tissue-dependent manner. Second, we have characterized the DNA methylome of visual disorders linked to internal and external environmental factors. Main conclusions allow certifying that crucial pathways related to Wnt-MAPK signaling pathways or neuroinflammation are epigenetically controlled in the fibrotic disorders involved in retinal detachment, but results also reinforced the contribution of neurovascularization (ETS1, HES5, PRDM16) in diabetic retinopathy. Finally, we had studied the methylome in the most frequent intraocular tumors in adults and children (uveal melanoma and retinoblastoma, respectively). We observed that hypermethylation of tumor suppressor genes is a frequent event in ocular tumors, but also unmethylation is associated with tumorogenesis. Interestingly, unmethylation of the proto-oncogen RAB31 was a predictor of metastasis risk in uveal melanoma. Loss of methylation of the oncogenic mir-17-92 cluster was detected in primary tissues but also in blood from patients. The research leading to these results was supported by European Research Council Advanced Grant EPINORC, RecerCaixa Foundation, Federación Española de Enfermedades Raras (FEDER), Federación Española de Enfermedades Neuromusculares (ASEM), Fundación Isabel Gemio, COST CM1406, Instituto de Salud Carlos III (PI/00816) and Health and Sciences Departments of the Catalan Government (Generalitat de Catalunya). M.E. is an Institució Catalana de Recerca i Estudis Avançats (ICREA) Research Professor. We thank the staff of the Biobank Facility at the Bellvitge Biomedical Research Institute (IDIBELL), Spanish National Cancer Research Center (CNIO), Institute of Rare Diseases Research (BioNER-ISCIII), Vall d’Hebron Research Institute (VHIR) and Banc de Sang i Teixits (BST) of the Catalan Ministry of Health. We also thank Dr. Mercedes Hurtado (Department of Ophthalmology, University and Polytechnic Hospital La Fe) and Dr. Dolores Pinazo (Department of Ophthalmology, Dr. Peset University Hospital) for obtaining samples from glaucomatous patients. We thank the patients and their families. Sí

Resume Une mutation des deux alleles du gene Rb , durant le developpement retinien normal, est responsable de l’apparition du retinoblastome. La recherche de mutation au niveau du gene Rb reste difficile, car la majorite des alterations sont uniques et dispersees tout au long du gene. Nous rapportons dans notre etude le resultat de l’analyse du gene Rb au niveau constitutionnel et tumoral dans la population algerienne. Notre etude a porte sur un echantillon de 21 patients atteints de retinoblastome. Le promoteur et les 27 exons, avec leurs sequences introniques flanquantes composant le gene Rb , ont ete amplifies et analyses par chromatographie liquide a haute performance (HPLC) suivie d’un sequencage. Les variations de bases identifiees au niveau constitutionnel et tumoral sont au nombre de sept : trois mutations non sens, une mutation affectant le site d’epissage, une deletion et deux polymorphismes. L’analyse du gene Rb a ete realisee chez des enfants atteints de retinoblastome ne presentant aucun antecedent familial de la maladie. Par cette etude, nous avons pu identifier deux cas sur les 21 etudies ayant un retinoblastome pouvant etre transmissible. Deux mutations rapportees n’ont jamais ete decrites par la litterature.

Inactivation of both alleles of the RB1 gene during normal retinal development initiates the formation of a retinoblastoma (RB) tumor. RB1 screening remains difficult, most of the alterations being unique and randomly distributed throughout the entire coding sequence. In this report, we present the results of a constitutionnal and tumoral RB1 analysis in Algerian population. The detection of RB1 gene deletion or mutation was performed by high performance liquid chromatography (HPLC) and sequence analyses in 21 patients. Germline abnormalities were found in 2/21 patients of sporadic unilateral retinoblastoma. The spectrum of germline and tumoral alterations included: three nonsense mutations; one mutation affecting splice site; one deletion and two polymorphisms. In general, for the 21 patients with no family history of the disease, we have identified mutations in germinal level in two of them showing that it is a transmissible form of retinoblastoma in these two cases known to be sporadic. A total of two mutations have not been previously reported.