Inhibition of DDR1 enhances in vivo chemosensitivity in KRAS-mutant lung adenocarcinoma

Platinum-based chemotherapy in combination with immune-checkpoint inhibitors is the current standard of care for patients with advanced lung adenocarcinoma (LUAD). However, tumor progression evolves in most cases. Therefore, predictive bioma ricers are needed for better patient stratification and for the identification of new therapeutic strategies, including enhancing the efficacy of chemotoxic agents. Here, we hypothesized that discoidin domain receptor 1 (DDR1) may be both a predictive factor for chemoresistance in patients with LUAD and a potential target positively selected in resistant cells. By using biopsies from patients with LUAD, KRAS-mutant LUAD cell lines, and in vivo genetically engineered KRAS-driven mouse models, we evaluated the role of DDR1 in the context of chemotherapy treatment. We found that DORT is upregulated during chemotherapy both in vitro and in viva. Moreover, analysis of a cohort of patients with LUAD suggested that high DOR1 levels in pretreatment biopsies correlated with poor response to chemotherapy. Additionally, we showed that combining DORI inhibition with chemotherapy prompted a synergistic therapeutic effect and enhanced cell death of KRAS-mutant tumors in vivo. Collectively, this study suggests a potential role for DDR1 as both a predictive and prognostic biomarker, potentially improving the chemotherapy response of patients with LUAD

Rôle des protéines Ssl3 et Ssl38 dans la transmission des chromosomes chez Schizosaccharomyces Pompe

La transmission fidèle des chromosomes lors des divisions mitotiques est essentielle à la stabilité du génome. En début de mitose, les chromosomes préalablement dupliqués en phase S condensent sous la forme de deux chromatides soeurs associées et les centromètres capturent les microtubulures du fuseau. Lors de la transition métaphase-anaphase, la cohésion des chromatides soeurs est éliminée, déclenchant leur migration vers les pôles opposés du fuseau. La cohésion est assurée par le complexe cohésine, chargé sur les chromosomes en phase G1 du cycle cellulaire et maintenu jusqu'en anaphase. Les mécanismes par lesquels les cohésines s'associent aux chromosomes et assurent la cohésion sont mal compris. Les centromères sont généralement constitués d'hétérochromatine, une forme compacte de la chromatine, dont l'assemblage fait intervenir la machinerie de RNAi. Des mutations affectant certains composants structuraux de l'hétérochromatine, comme Swi6/HP1 chez Saccharomyces pombe, altèrent la ségrégation des chromosomes en mitose. Afin d'appréhender les rôles de Swi6, ses partenaires fonctionnels ont été recherchés par un crible génétique. Ici, je présente l'étude des gènes ss13 et ss138 (swi6 synthétique létal). Le gène ss13 code un facteur de chargement des cohésines en phase G1 du cycle cellulaire, dont la fonction est conservée au cours de l'évolution. Etonnament, ss138 code un composant du spliceosome. Les résultats présentés montrent que Ss138 est nécessaire à l'intégrité de l'hétérochromatine centromérique. La signification biologique du lien entre Ss138, la maturation des ARNs, et l'assemblage de l'hétérochromatine centrométrique est discutée.In all eukaryotes, the genome stability relies on accurate chromosome segregation throughout mitotic divisions. During early mitosis, each duplicated chromosomes condense into a pair of tightly linked sister chromatids and centromeres capture spindle microtubules. At the metaphase to anaphase transition, cohesion between sister chromatids is removed, triggering their migration towards the opposite spindle poles. Sister chromatid cohesion is ensured by cohesin, a proteinaceous complex loaded onto chromosomes in G1 and maitained chromosomally bound until anaphase onset. The mechanisms through which cohesin is loaded onto chromosomes and ensures cohesion are ill defined.In most eukaryotes, centromeres are made of heterochromatin : a specialized form of chromatin whose assembly and maintenance rely on the RNAi pathway. Mutations affecting structural components of heterochromatin, such as Swi6/HP1 in fission yeast, impair chromosome segregation. In order to investigate the biological functions of Swi6, its functional partners were sought through a genetic screen. Here I report on the study of ss13 and ss138 (swi6 synthetic lethal). The ss13 gene encodes a cohesin loading factor, whose function in G1 in evolutionarily conserved. Unexpectedly, ss138 encodes a spliceosome component. Experimental data indicate that ss138 is essential for centrometric heterochromatin integrity and accurate chromosome segregation. The biological significance of a link between Ss138, RNA modifications and the assembly of centrometric heterochromatin is discussed.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

Distinct requirement of RNA polymerase II CTD phosphorylations in budding and fission yeast

The "CTD code" links the combinatorial potential of the modifications found on the Rpb1 C-terminal domain (CTD) to the growing group of CTD binding effectors. The genetic dissection of serine 2 and serine 7 function within the CTD in both budding and fission yeast reveals distinct in vivo requirement

Splicing Factor Spf30 Assists Exosome-Mediated Gene Silencing in Fission Yeast▿

Heterochromatin assembly in fission yeast relies on the processing of cognate noncoding RNAs by both the RNA interference and the exosome degradation pathways. Recent evidence indicates that splicing factors facilitate the cotranscriptional processing of centromeric transcripts into small interfering RNAs (siRNAs). In contrast, how the exosome contributes to heterochromatin assembly and whether it also relies upon splicing factors were unknown. We provide here evidence that fission yeast Spf30 is a splicing factor involved in the exosome pathway of heterochromatin silencing. Spf30 and Dis3, the main exosome RNase, colocalize at centromeric heterochromatin and euchromatic genes. At the centromeres, Dis3 helps recruiting Spf30, whose deficiency phenocopies the dis3-54 mutant: heterochromatin is impaired, as evidenced by reduced silencing and the accumulation of polyadenylated centromeric transcripts, but the production of siRNAs appears to be unaffected. Consistent with a direct role, Spf30 binds centromeric transcripts and locates at the centromeres in an RNA-dependent manner. We propose that Spf30, bound to nascent centromeric transcripts, perhaps with other splicing factors, assists their processing by the exosome. Splicing factor intercession may thus be a common feature of gene silencing pathways

Cdk11-CyclinL Controls the Assembly of the RNA Polymerase II Mediator Complex

The large Mediator (L-Mediator) is a general coactivator of RNA polymerase II transcription and is formed by the reversible association of the small Mediator (S-Mediator) and the kinase-module-harboring Cdk8. It is not known how the kinase module association/dissociation is regulated. We describe the fission yeast Cdk11-L-type cyclin pombe (Lcp1) complex and show that its inactivation alters the global expression profile in a manner very similar to that of mutations of the kinase module. Cdk11 is broadly distributed onto chromatin and phosphorylates the Med27 and Med4 Mediator subunits on conserved residues. The association of the kinase module and the S-Mediator is strongly decreased by the inactivation of either Cdk11 or the mutation of its target residues on the Mediator. These results show that Cdk11-Lcp1 regulates the association of the kinase module and the S-Mediator to form the L-Mediator complex

Cell-cycle regulation of cohesin stability along fission yeast chromosomes

International audienc