Normal cell cycle progression requires negative regulation of E2F1 by Groucho during S phase and its relief at G2 phase

The cell cycle depends on a sequence of steps that are triggered and terminated via the synthesis and degradation of phase-specific transcripts and proteins. Although much is known about how stage-specific transcription is activated, less is understood about how inappropriate gene expression is suppressed. Here, we demonstrate that Groucho, the Drosophila orthologue of TLE1 and other related human transcriptional corepressors, regulates normal cell cycle progression in vivo. We show that, although Groucho is expressed throughout the cell cycle, its activity is selectively inactivated by phosphorylation, except in S phase when it negatively regulates E2F1. Constitutive Groucho activity, as well as its depletion and the consequent derepression of e2f1, cause cell cycle phenotypes. Our results suggest that Cdk1 contributes to phase-specific phosphorylation of Groucho in vivo. We propose that Groucho and its orthologues play a role in the metazoan cell cycle that may explain the links between TLE corepressors and several types of human cancer

MTADV 5-MER peptide suppresses chronic inflammations as well as autoimmune pathologies and unveils a new potential target-Serum Amyloid A.

Despite the existence of potent anti-inflammatory biological drugs e.g., anti-TNF and anti IL-6 receptor antibodies, for treating chronic inflammatory and autoimmune diseases, these are costly and not specific. Cheaper oral available drugs remain an unmet need. Expression of the acute phase protein Serum Amyloid A (SAA) is dependent on release of pro-inflammatory cytokines IL-1, IL-6 and TNF-α during inflammation. Conversely, SAA induces pro-inflammatory cytokine secretion, including Th17, leading to a pathogenic vicious cycle and chronic inflammation. 5- MER peptide (5-MP) MTADV (methionine-threonine-alanine-aspartic acid-valine), also called Amilo-5MER, was originally derived from a sequence of a pro-inflammatory CD44 variant isolated from synovial fluid of a Rheumatoid Arthritis (RA) patient. This human peptide displays an efficient anti-inflammatory effects to ameliorate pathology and clinical symptoms in mouse models of RA, Inflammatory Bowel Disease (IBD) and Multiple Sclerosis (MS). Bioinformatics and qRT-PCR revealed that 5-MP, administrated to encephalomyelytic mice, up-regulates genes contributing to chronic inflammation resistance. Mass spectrometry of proteins that were pulled down from an RA synovial cell extract with biotinylated 5-MP, showed that it binds SAA. 5-MP disrupted SAA assembly, which is correlated with its pro-inflammatory activity. The peptide MTADV (but not scrambled TMVAD) significantly inhibited the release of pro-inflammatory cytokines IL-6 and IL-1β from SAA-activated human fibroblasts, THP-1 monocytes and peripheral blood mononuclear cells. 5-MP suppresses the pro-inflammatory IL-6 release from SAA-activated cells, but not from non-activated cells. 5-MP could not display therapeutic activity in rats, which are SAA deficient, but does inhibit inflammations in animal models of IBD and MS, both are SAA-dependent, as shown by others in SAA knockout mice. In conclusion, 5-MP suppresses chronic inflammation in animal models of RA, IBD and MS, which are SAA-dependent, but not in animal models, which are SAA-independent

RNA-Seq of early follicle cells – EGFRact Rep1 Read2

Paired-end RNA-Sequencing data from early follicle cells Genotype 109-30-Gal4, UAS-mCD8::GFP, UAS-EGFR[lambda]top Replicate #1, Read

Data from: Phosphorylated Groucho delays differentiation in the follicle stem cell lineage by providing a molecular memory of EGFR signaling in the niche

In the epithelial follicle stem cells (FSCs) of the Drosophila ovary, Epidermal Growth Factor Receptor (EGFR) signaling promotes self-renewal, whereas Notch signaling promotes differentiation of the prefollicle cell (pFC) daughters. We have identified two proteins, Six4 and Groucho (Gro), that link the activity of these two pathways to regulate the earliest cell fate decision in the FSC lineage. Our data indicate that Six4 and Gro promote differentiation towards the polar cell fate by promoting Notch pathway activity. This activity of Gro is antagonized by EGFR signaling, which inhibits Gro-dependent repression via p-ERK mediated phosphorylation. We have found that the phosphorylated form of Gro persists in newly formed pFCs, which may delay differentiation and provide these cells with a temporary memory of the EGFR signal. Collectively, these findings demonstrate that phosphorylated Gro labels a transition state in the FSC lineage and describe the interplay between Notch and EGFR signaling that governs the differentiation processes during this period

Novel interplay between JNK and Egfr signaling in <i>Drosophila</i> dorsal closure

<div><p>Dorsal closure (DC) is a developmental process in which two contralateral epithelial sheets migrate to seal a large hole in the dorsal ectoderm of the <i>Drosophila</i> embryo. Two signaling pathways act sequentially to orchestrate this dynamic morphogenetic process. First, c-Jun N-terminal kinase (JNK) signaling activity in the dorsal-most leading edge (LE) cells of the epidermis induces expression of <i>decapentaplegic</i> (<i>dpp</i>). Second, Dpp, a secreted TGF-β homolog, triggers cell shape changes in the adjacent, ventrally located lateral epidermis, that guide the morphogenetic movements and cell migration mandatory for DC. Here we uncover a cell non-autonomous requirement for the Epidermal growth factor receptor (Egfr) pathway in the lateral epidermis for sustained <i>dpp</i> expression in the LE. Specifically, we demonstrate that Egfr pathway activity in the lateral epidermis prevents expression of the gene <i>scarface</i> (<i>scaf</i>), encoding a secreted antagonist of JNK signaling. In embryos with compromised Egfr signaling, upregulated Scaf causes reduction of JNK activity in LE cells, thereby impeding completion of DC. Our results identify a new developmental role for Egfr signaling in regulating epithelial plasticity via crosstalk with the JNK pathway.</p></div

Egfr signaling is positively required for the full expression of the JNK pathway target gene <i>dpp</i> and for Mad phosphorylation.

<p>(A-F) Lateral (A, B, D, E) or dorsolateral (C, F) views of embryos hybridized using a digoxigenin-labeled RNA probe for <i>dpp</i> (blue). (A’-F’) Corresponding magnified views of the regions marked by black arrowheads in panels (A-F). (A”-F”) show embryos stained for pMad (red). (A-A”) Wild-type embryo showing the normal <i>dpp</i> (A-A’) and pMad (A”) patterns. Levels of <i>dpp</i> and pMad are reduced in <i>rhomboid</i> mutants (D-D”), as well as in embryo expressing <i>pnr>Egfr</i>^<i>DN</i> (E- E”). Conversely, both expand in embryo expressing <i>pnr>Ras</i>^<i>V12</i> (F- F”). These effects largely phenocopy loss- or gain-of-function JNK signaling (<i>bsk</i> mutant and <i>pnr>Hep</i>^<i>Act</i> embryo in B-B” and C-C”, respectively).</p

Dorsal closure is defective in embryos deficient for Egfr signaling.

<p>(A-H) Cuticle preparations. (A) Wild-type cuticle; note the complete closure of the epidermis on the dorsal side. (B) <i>bsk</i> mutant embryo; note the characteristic dorsal-open phenotype (arrowhead). (C-H) Lack of functional Egfr signaling leads to the formation of dorsal-open holes (arrowheads), a phenotype typically associated with JNK pathway mutants (cf. B). Egfr pathway activity was compromised by <i>pnr>Gal4</i>-driven ectodermal expression of <i>Egfr</i>^<i>DN</i> (C) or <i>Ras</i>^<i>DN</i> (D), or in <i>rhomboid</i> (E), <i>spi</i> (F) and allelic <i>Egfr</i> (G-H) mutant embryos.</p

EGFR signaling takes place in the lateral epidermis of stage 13 embryos, at the time of dorsal closure.

<p>(A) A schematic lateral view of a stage 13 embryo (st13; 9:20–10:20 hours after egg lay). Demarcated are three groups of cells that participate in the process of DC: the amnioserosa (yellow), the dorsal-most row of ectodermal cells termed leading edge cells (green) and the adjacent lateral epidermis cells (red). (B-D) A <i>rhomboid</i>-<i>lacZ</i> enhancer-trap embryo co-stained for dpErk (B; red) and LacZ (C; green). (D) Merge. (B, D) dpErk staining is evident in the lateral epidermis. (C, D) dpErk staining borders on <i>lacZ</i> expression. (E-I) dpErk staining (red) is greatly reduced in the lateral epidermis of embryos expressing <i>pnr>Egfr</i>^<i>DN</i> (E), or in embryos mutant for <i>rhomboid</i> (F), <i>spi</i> (G) and <i>Egfr</i> (H), though not in <i>pvr</i> mutants (I). In (E) and (H), the signal in the AS is an artifact caused by auto-florescence. In this and all other Figures, embryos are at st13 and presented in lateral views, with anterior to the left and dorsal up, unless otherwise stated.</p

Over-expression of <i>scarface</i> mimics the loss of Egfr pathway activity.

<p>(A-B) Embryos hybridized using a digoxigenin-labeled RNA probe for <i>dpp</i> (blue). Over-expression of <i>scaf</i> brings about a reduction in <i>dpp</i> expression (A) whereas <i>dpp</i> expression expands in <i>scaf</i> mutant embryos (B), similarly to loss- and gain-of-function mutations in the Egfr pathway, respectively. (C-F) Embryos stained for pMad (red). (C, D) In keeping with <i>dpp</i> expression levels, pMad staining decreases upon <i>scaf</i> over-expression (C), and is augmented in a <i>scaf</i> mutant (D). (E, F) Although pMad staining is reduced in <i>rhomboid</i> single mutant embryo (E), it expands in embryo doubly mutant for <i>scaf</i> and <i>rhomboid</i> (F), as in <i>scaf</i> single mutant (D), indicating that <i>scaf</i> is epistatic to <i>Egfr</i> signaling. (G-H) Model showing how Egfr signaling in the lateral epidermis positively and non-autonomously contributes to JNK pathway activity in LE cells and to DC. (G) The Egfr pathway normally acts in the lateral epidermis to prevent expression of the JNK antagonist, <i>scaf</i>, thus supporting maximal JNK activity in LE cells. (H) When Egfr signaling is defective, deregulated Scaf subsequently attenuates functional JNK signaling in LE cells, thus hindering the process of DC. Bold text and arrows/bars indicate normal levels of gene expression and regulation, whereas gray fonts designate abnormally lower levels of expression and regulation, respectively.</p

The Egfr pathway induces expression of Engrailed, a <i>scarface</i> repressor, in the lateral epidermis.

<p>(A, A’) Cuticle preparation. Dark (A) and bright field (A’) images of an embryo expressing <i>pnr>Yan</i>^<i>Act</i>. Note the dorsal open hole. (B, C) Embryos expressing <i>pnr>Yan</i>^<i>Act</i>, hybridized using a digoxigenin-labeled RNA probe for <i>dpp</i> (blue; B) or stained for pMad (red; C). (B’) Magnified view of the region marked by a rectangle in (B). Note that Yan^Act brings about a reduction in <i>dpp</i> expression and, as a consequence, a reduction in the pMad domain, similarly to other <i>Egfr</i> pathway mutants. (D) Embryo expressing <i>pnr>Yan</i>^<i>Act</i> hybridized using a digoxigenin-labeled RNA probe for <i>scaf</i> (blue). (D’) Magnified view of the region marked by a rectangle in (D). Note that <i>scaf</i> expression expands into the lateral epidermis. (E, F) Yan^ACT dominantly represses En. Control embryo expressing <i>pnr>GFP</i> (E) and embryo expressing <i>pnr>Yan</i>^<i>Act</i> (F) stained for En (green), as well as for LacZ (magenta; <i>puc-lacZ</i>) to mark the LE. Yan^ACT activity reduces En expression in the LacZ-positive LE cells, as well as in the adjacent lateral epidermis (F). (G) Model explaining how Egfr signaling prevents expression of <i>scaf</i> in the lateral epidermis.</p