JUN Oncogene Amplification and Overexpression Block Adipocytic Differentiation in Highly Aggressive Sarcomas

SummaryThe human oncogene JUN encodes a component of the AP-1 complex and is consequently involved in a wide range of pivotal cellular processes, including cell proliferation, transformation, and apoptosis. Nevertheless, despite extensive analyses of its functions, it has never been directly involved in a human cancer. We demonstrate here that it is highly amplified and overexpressed in undifferentiated and aggressive human sarcomas, which are blocked at an early step of adipocyte differentiation. We confirm by cellular and xenograft mouse models recapitulating these sarcoma genetics that the failure to differentiate is dependent upon JUN amplification/overexpression

Implication de Cak1 (CDK activating kinase) dans le processus de transcription par l'ARN polymérase II chez Saccharomyces cerevisiae

Chez la levure S.cerevisiae, les rôles physiologiques connus de la protéine essentielle Cak1 (kinase activatrice des kinases cycline-dépendantes (CDK)) sont de phosphoryler Cdc28, régulateur majeur du cycle cellulaire, ainsi que Kin28, kinase du domaine carboxy-terminal de la plus grosse sous-unité de l'ARN polymérase II. Des mutants conditionnels de cakI semblent affectés dans le contrôle du cycle cellulaire, mais aussi dans la formation de la paroi des spores, la différentiation pseudohyphale, ainsi que dans la réponse au stress osmotique. Dans ce travail, nous avons montré que Cak1 est impliquée dans le processus de transcription non seulement via la phosphorylation de Kin28, mais également via le complexe transcriptionnel multimérique Paf1 et via la protéine Ssu72. Une étude plus poussée de Ssu72 nous a permis de dévoiler sa nature de protéine phosphatase, et les liens étroits, tant génétiques que moléculaires, qu'elle tisse avec plusieurs autres protéines impliquées dans l'expression des gènes, telles que Sua7 (TFIIB), Kin28, Pafl, Ctr9 ou Fcp1. La multiplicité des effets des mutations dans le gène CAK1 pourrait ainsi s'expliquer par un rôle de modulateur de l'activité de transcription.In the budding yeast S.cerevisae, the known physiological roles of the essential protein Cak1 (Cyclin-dependant kinases (CDKs) Activating Kinase) are to phosphorylate Cdc28, the main regulator of progression through cell cycle, and Kin28, the carboxy-terminal domain (CTD) kinase of the largest RNA polymerase II subunit. Conditionnal mutants of cakl appear affected in cell cycle control, but also in spore-wall morphogenesis, pseudohyphal differentiation, and response to high osmolarity. In this work, we show that Cak1 is implicated in transcription process not only through Kin28 phosphorylation, but also through the multimeric transcriptional complex Paf1 and the Ssu72 protein. A more extensive study of Ssu72 enabled us to reveal its phosphatase activity, as well as its genetic and molecular interactions with several other proteins involved in gene expression, such as Sua7 (TFIIB), Kin28, Paf1, Ctr9 or Fcp1. Thus, the multiple effects of cakl mutations could be explained by the role of Cak1 as a modulator of transcriptional activity.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

tRNA processing defects induce replication stress and Chk2-dependent disruption of piRNA transcription

International audienceRNase P is a conserved endonuclease that processes the 50 trailer of tRNA precursors. We have isolated mutations in Rpp30, a subunit of RNase P, and find that these induce complete sterility in Drosophila females. Here, we show that sterility is not due to a shortage of mature tRNAs, but that atrophied ovaries result from the activation of several DNA damage checkpoint proteins, including p53, Claspin, and Chk2. Indeed, we find that tRNA processing defects lead to increased replication stress and de-repression of transposable elements in mutant ovaries. We also report that transcription of major piRNA sources collapse in mutant germ cells and that this correlates with a decrease in heterochromatic H3K9me3 marks on the corresponding piRNA-producing loci. Our data thus link tRNA processing, DNA replication, and genome defense by small RNAs. This unexpected connection reveals constraints that could shape genome organization during evolution

Ssu72 is a phosphatase essential for transcription termination of snoRNAs and specific mRNAs in yeast

Ssu72 is an essential yeast protein that is involved in transcription. It physically interacts with transcription initiation and termination complexes. In this report, we provide evidence that Ssu72 is a phosphatase that physically interacts with the CTD kinase Kin28 and functionally interacts with the CTD phosphatase Fcp1. A genome-wide expression analysis of mutant ssu72-ts69 during growth in complete medium revealed a number of defects, including the accumulation of a limited number of mRNAs and the read-through transcription of small nucleolar RNAs and of some mRNAs. We hypothesize that Ssu72 plays a key role in the transcription termination of certain transcripts, possibly by promoting RNA polymerase pausing and release. The possibility that the CTD of the largest subunit of RNA polymerase II is a substrate of Ssu72 is discussed

Small AntiMicrobial Peptide with In Vivo Activity Against Sepsis

Antimicrobial peptides (AMPs) are considered as potential therapeutic sources of future antibiotics because of their broad-spectrum activities and alternative mechanisms of action compared to conventional antibiotics. Although AMPs present considerable advantages over conventional antibiotics, their clinical and commercial development still have some limitations, because of their potential toxicity, susceptibility to proteases, and high cost of production. To overcome these drawbacks, the use of peptides mimics is anticipated to avoid the proteolysis, while the identification of minimalist peptide sequences retaining antimicrobial activities could bring a solution for the cost issue. We describe here new polycationic -amino acids combining these two properties, that we used to design small dipeptides that appeared to be active against Gram-positive and Gram-negative bacteria, selective against prokaryotic versus mammalian cells, and highly stable in human plasma. Moreover, the in vivo data activity obtained in septic mice reveals that the bacterial killing effect allows the control of the infection and increases the survival rate of cecal ligature and puncture (CLP)-treated mice

Synthesis and antimicrobial evaluation of amphiphilic neamine derivatives

The aminoglycoside antibiotics bind to the 16S bacterial rRNA and disturb the protein synthesis. One to four hydroxyl functions of the small aminoglycoside neamine were capped with phenyl, naphthyl, pyridyl, or quinolyl rings. The 3',4- (6), 3',6- (7a), and the 3',4',6- (10a) 2-naphthylmethylene derivatives appeared to be active against sensitive and resistant Staphylococcus aureus strains. 10a also showed marked antibacterial activities against Gram (-) bacteria, including strains expressing enzymes modifying aminoglycosides, efflux pumps, or rRNA methylases. 7a and 10a revealed a weak and aspecific binding to a model bacterial 16S rRNA. Moreover, its compared to neomycin B, 10a showed a lower ability to decrease H-3 leucine incorporation into proteins in Pseudomonas aeruginosa. All together, out, results suggest that the 3',4,6-tri-2-naphthylmethylene neamine derivative 10a should act against Gram (-) bacteria through it mechanism different from inhibition of protein synthesis, probably by membrane destabilization