FIRRM/C1orf112 is synthetic lethal with PICH and mediates RAD51 dynamics

Joint DNA molecules are natural byproducts of DNA replication and repair. Persistent joint molecules give rise to ultrafine DNA bridges (UFBs) in mitosis, compromising sister chromatid separation. The DNA translocase PICH (ERCC6L) has a central role in UFB resolution. A genome-wide loss-of-function screen is performed to identify the genetic context of PICH dependency. In addition to genes involved in DNA condensation, centromere stability, and DNA-damage repair, we identify FIGNL1-interacting regulator of recombination and mitosis (FIRRM), formerly known as C1orf112. We find that FIRRM interacts with and stabilizes the AAA + ATPase FIGNL1. Inactivation of either FIRRM or FIGNL1 results in UFB formation, prolonged accumulation of RAD51 at nuclear foci, and impaired replication fork dynamics and consequently impairs genome maintenance. Combined, our data suggest that inactivation of FIRRM and FIGNL1 dysregulates RAD51 dynamics at replication forks, resulting in persistent DNA lesions and a dependency on PICH to preserve cell viability. </p

Structure–property relationships in normal and mixed dithienylethenes – polyoxometalates supramolecular assemblies with fast solid-state photochromic properties

International audienceFive new highly photochromic hybrid organic-inorganic materials were successfully prepared by supramolecular assembly of normal (1+) and mixed (2+) cationic dithienylethenes (DTEs) and polyoxometalates (POMs) units. Single-crystal X-ray diffraction studies reveal that (1)3[PM12O40]∙5ACN (M = W, Mo) (1-PW12 and 1-PMo12) and (2)3[PM12O40]∙5ACN (M = W, Mo) (2-PW12 and 2-PMo12) are isostructural, while (2)4[Mo8O26]4DMF (2-Mo8) is an isotype of (1)4[Mo8O26]4DMF (1-Mo8) i.e., the first POM-DTE ionic assembly, recently reported. The solid-state photochromic properties of these materials at room temperature are highly tunable with the nature of the DTEs and POMs used, which has been interpreted taking into account steric and electronic factors. Especially, while 1-PMo12 and 2-PMo12 exhibit negligible photoresponses which have not been considered herein, thorough investigations of the photocoloration and fading kinetics in ambient conditions have highlighted the precise impact of both organic and inorganic components on the photoswitching abilities of 1-Mo8, 2-Mo8, 1-PW12 and 2-PW12. Upon UV-light irradiation, the absorption of the normal and mixed DTEs in their closed-ring form exhibits a hypsochromic shift which is more pronounced in hybrid systems integrating -[Mo8O26]4- rather than -[PW12O40]3-, due to the higher negative charge density of the octamolybdate unit. The photocyclization rates of DTEs are also systematically increased when combined with the -[Mo8O26]4- unit, while in contrast, their back cycloreversion rates are not affected whatever the nature of the POMs used. In addition, within isostructural series, hybrids integrating mixed DTEs exhibit faster fading processes than their normal DTE counterparts when exposed to visible light. Finally, among this new series, 2-Mo8 shows the best photochromic performances with a fast photocoloration rate associated with a high coloration contrast, a fast and complete fading process and a high cyclability

The SRC-family tyrosine kinase HCK shapes the landscape of SKAP2 interactome

International audienceThe SRC Kinase Adaptor Phosphoprotein 2 (SKAP2) is a broadly expressed adaptor associated with the control of actin-polymerization, cell migration, and oncogenesis. After activation of different receptors at the cell surface, this dimeric protein serves as a platform for assembling other adaptors such as FYB and some SRC family kinase members, although these mechanisms are still poorly understood. The goal of this study is to map the SKAP2 interactome and characterize which domains or binding motifs are involved in these interactions. This is a prerequisite to finely analyze how these pathways are integrated in the cell machinery and to study their role in cancer and other human diseases when this network of interactions is perturbed. In this work, the domain and the binding motif of fourteen proteins interacting with SKAP2 were precisely defined and a new interactor, FAM102A was discovered. Herein, a fine-tuning between the binding of SRC kinases and their activation was identified. This last process, which depends on SKAP2 dimerization, indirectly affects the binding of FYB protein. Analysis of conformational changes associated with activation/inhibition of SRC family members, presently limited to their effect on kinase activity, is extended to their interactive network, which paves the way for therapeutic development. www.impactjournals.com/oncotarget

Enhanced reversible solid-state photoswitching of a cationic dithienylethene assembled with a polyoxometalate unit

International audienceThe first photochromic supramolecular assembly of a dithienylethene (DTE) cation with a polyoxometalate (POM) is elaborated. The POM unit modifies the photoswitching of the DTE in the solid state, via both steric and electronic effects, resulting in an increase of its cycloreversion rate, and an almost complete re-opening process. The crystal structure after exposure to UV light reveals a remarkable photocyclization yield of almost 28%. The structural model was greatly improved by theoretical calculations, and the absorption properties were nicely modeled from electronic structure calculations

A CRISPR-Cas9 screen identifies EXO1 as a formaldehyde resistance gene

Fanconi Anemia (FA) is a rare, genome instability-associated disease characterized by a deficiency in repairing DNA crosslinks, which are known to perturb several cellular processes, including DNA transcription, replication, and repair. Formaldehyde, a by-product of metabolism, is thought to drive FA by generating DNA interstrand crosslinks (ICLs) and DNA-protein crosslinks (DPCs). However, the impact of formaldehyde on global cellular pathways has not been investigated thoroughly. Herein, using a pangenomic CRISPR-Cas9 screen, we identify EXO1 as a critical regulator of formaldehyde-induced DNA lesions. We show that EXO1 knockout cell lines exhibit formaldehyde sensitivity leading to the accumulation of replicative stress, DNA double-strand breaks, and quadriradial chromosomes, a typical feature of FA. After formaldehyde exposure, EXO1 is recruited to chromatin, protects DNA replication forks from degradation, and functions in parallel with the FA pathway to promote cell survival. In vitro, EXO1-mediated exonuclease activity is proficient in removing DPCs. Collectively, we show that EXO1 limits replication stress and DNA damage to counteract formaldehyde-induced genome instability.</p