2022

The DEAD box RNA helicase DDX42 is an intrinsic inhibitor of positive-strand RNA viruses.: Author(s) : Bonaventure B, Rebendenne A, Chaves Valadão A, Arnaud-Arnould M, Gracias S, Garcia de Gracia F, McKellar J, Labaronne E, Tauziet M, Vivet-Boudou V, Bernard E, Briant L, Gros N, Djilli W, Courgnaud V, Parrinello H, Rialle S, Blaise M, Lacroix L, Lavigne M, Paillart J, Ricci E, Schulz R, Jouvenet N, Moncorgé O, Goujon C,; Journal : EMBO Rep; 2022; Genome-wide screens are powerful approaches to unravel regulators of viralinfections. Here, a CRISPR screen identifies the RNA helicase DDX42 as anintrinsic antiviral inhibitor of HIV-1. Depletion of endogenous DDX42 increasesHIV-1 DNA accumulation and infection in cell lines and primary cells. DDX42overexpression inhibits HIV-1 infection, whereas expression of adominant-negative mutant increases infection. Importantly, DDX42 also restrictsLINE-1 retrotransposition and infection with other retroviruses andpositive-strand RNA viruses, including CHIKV and SARS-CoV-2. However, DDX42 doesnot impact the replication of several negative-strand RNA viruses, arguingagainst an unspecific effect on target cells, which is confirmed by RNA-seqanalysis. Proximity ligation assays show DDX42 in the vicinity of viral elements,and cross-linking RNA immunoprecipitation confirms a specific interaction ofDDX42 with RNAs from sensitive viruses. Moreover, recombinant DDX42 inhibitsHIV-1 reverse transcription in vitro. Together, our data strongly suggest adirect mode of action of DDX42 on viral ribonucleoprotein complexes. Our resultsidentify DDX42 as an intrinsic viral inhibitor, opening new perspectives totarget the life cycle of numerous RNA viruses.
The trophectoderm acts as a niche for the inner cell mass through C/EBPα-regulated IL-6 signaling: Author(s) : Plana-Carmona M, Stik G, Bulteau R, Segura-Morales C, Alcázar N, Wyatt C, Klonizakis A, de Andrés-Aguayo L, Gasnier M, Tian T, Torcal Garcia G, Vila-Casadesús M, Plachta N, Serrano M, Francesconi M, Graf T,; Journal : Stem Cell Reports; 2022; IL-6 has been shown to be required for somatic cell reprogramming into induced pluripotent stem cells (iPSCs). However, how Il6 expression is regulated and whether it plays a role during embryo development remains unknown. Here, we describe that IL-6 is necessary for C/EBPα-enhanced reprogramming of B cells into iPSCs but not for B cell to macrophage transdifferentiation. C/EBPα overexpression activates both Il6 and Il6ra genes in B cells and in PSCs. In embryo development, Cebpa is enriched in the trophectoderm of blastocysts together with Il6, while Il6ra is mostly expressed in the inner cell mass (ICM). In addition, Il6 expression in blastocysts requires Cebpa. Blastocysts secrete IL-6 and neutralization of the cytokine delays the morula to blastocyst transition. The observed requirement of C/EBPα-regulated IL-6 signaling for pluripotency during somatic cell reprogramming thus recapitulates a physiologic mechanism in which the trophectoderm acts as niche for the ICM through the secretion of IL-6.
Three classes of epigenomic regulators converge to hyperactivate the essential maternal gene deadhead within a heterochromatin mini-domain.: Author(s) : Torres-Campana D, Horard B, Denaud S, Benoit G, Loppin B, Orsi G,; Journal : PLoS Genet; 2022; The formation of a diploid zygote is a highly complex cellular process that isentirely controlled by maternal gene products stored in the egg cytoplasm. Thishighly specialized transcriptional program is tightly controlled at the chromatinlevel in the female germline. As an extreme case in point, the massive and specificovarian expression of the essential thioredoxin Deadhead (DHD) is criticallyregulated in Drosophila by the histone demethylase Lid and its partner, the histonedeacetylase complex Sin3A/Rpd3, via yet unknown mechanisms. Here, we identified Snr1and Mod(mdg4) as essential for dhd expression and investigated how these epigenomiceffectors act with Lid and Sin3A to hyperactivate dhd. Using Cut&Run chromatinprofiling with a dedicated data analysis procedure, we found that dhd isintriguingly embedded in an H3K27me3/H3K9me3-enriched mini-domain flanked by DNAregulatory elements, including a dhd promoter-proximal element essential for itsexpression. Surprisingly, Lid, Sin3a, Snr1 and Mod(mdg4) impact H3K27me3 and thisregulatory element in distinct manners. However, we show that these effectorsactivate dhd independently of H3K27me3/H3K9me3, and that dhd remains silent in theabsence of these marks. Together, our study demonstrates an atypical and criticalrole for chromatin regulators Lid, Sin3A, Snr1 and Mod(mdg4) to triggertissue-specific hyperactivation within a unique heterochromatin mini-domain.
Titration of Apparent In-Cellula Affinities of Protein-Protein Interactions.: Author(s) : Cluet D, Vergier B, Levy N, Dehau L, Thurman A, Amri I, Spichty M,; Journal : Chembiochem; 2022; A genetic assay permits simultaneous quantification of two interacting proteinsand their bound fraction at the single-cell level using flow cytometry. Apparentin-cellula affinities of protein-protein interactions can be extracted from theacquired data through a titration-like analysis. The applicability of thisapproach is demonstrated on a diverse set of interactions with proteins fromdifferent families and organisms and with in-vitro dissociation constants rangingfrom picomolar to micromolar.

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2022

The DEAD box RNA helicase DDX42 is an intrinsic inhibitor of positive-strand RNA viruses.

The trophectoderm acts as a niche for the inner cell mass through C/EBPα-regulated IL-6 signaling

Three classes of epigenomic regulators converge to hyperactivate the essential maternal gene deadhead within a heterochromatin mini-domain.

Titration of Apparent In-Cellula Affinities of Protein-Protein Interactions.

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