title: Mariner Transposons Contain a Silencer: Possible Role of the Polycomb Repressive Complex 2.
abstract: Transposable elements are driving forces for establishing genetic innovations such as transcriptional regulatory networks in eukaryotic genomes. Here, we describe a silencer situated in the last 300 bp of the Mos1 transposase open reading frame (ORF) which functions in vertebrate and arthropod cells. Functional silencers are also found at similar locations within three other animal mariner elements, i.e. IS630-Tc1-mariner (ITm) DD34D elements, Himar1, Hsmar1 and Mcmar1. These silencers are able to impact eukaryotic promoters monitoring strong, moderate or low expression as well as those of mariner elements located upstream of the transposase ORF. We report that the silencing involves at least two transcription factors (TFs) that are conserved within animal species, NFAT-5 and Alx1. These cooperatively act with YY1 to trigger the silencing activity. Four other housekeeping transcription factors (TFs), neuron restrictive silencer factor (NRSF), GAGA factor (GAF) and GTGT factor (GTF), were also found to have binding sites within mariner silencers but their impact in modulating the silencer activity remains to be further specified. Interestingly, an NRSF binding site was found to overlap a 30 bp motif coding a highly conserved PHxxYSPDLAPxD peptide in mariner transposases. We also present experimental evidence that silencing is mainly achieved by co-opting the host Polycomb Repressive Complex 2 pathway. However, we observe that when PRC2 is impaired another host silencing pathway potentially takes over to maintain weak silencer activity. Mariner silencers harbour features of Polycomb Response Elements, which are probably a way for mariner elements to self-repress their transcription and mobility in somatic and germinal cells when the required TFs are expressed. At the evolutionary scale, mariner elements, through their exaptation, might have been a source of silencers playing a role in the chromatin configuration in eukaryotic genomes.
authors.affiliation: PRC, UMR INRA-CNRS 7247, PRC, Nouzilly, France.|Institute of Biotechnology, University of Lausanne, and Center for Biotechnology UNIL-EPFL, Lausanne, Switzerland.
authors.forename: Solenne
authors.initials: S
authors.lastname: Bire
authors.affiliation: PRC, UMR INRA-CNRS 7247, PRC, Nouzilly, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Casteret
authors.affiliation: PRC, UMR INRA-CNRS 7247, PRC, Nouzilly, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Piégu
authors.affiliation: PRC, UMR INRA-CNRS 7247, PRC, Nouzilly, France.
authors.forename: Linda
authors.initials: L
authors.lastname: Beauclair
authors.affiliation: UMR INRA 1282, ISP, Parc de Grandmont, Tours, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Moiré
authors.affiliation: Biological Sciences Department, California State Polytechnic University, Pomona, California, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Arensbuger
authors.affiliation: PRC, UMR INRA-CNRS 7247, PRC, Nouzilly, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Bigot
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D002843:Chromatin / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D016678:Genome; D006367:HeLa Cells; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D050778:NFATC Transcription Factors / Q000235:genetics; D063151:Polycomb Repressive Complex 2 / Q000235:genetics* / Q000378:metabolism; D037941:Silencer Elements, Transcriptional / Q000235:genetics*; D019895:Transposases / Q000235:genetics* / Q000378:metabolism
chemical_list: C489985:ALX1 protein, human; D002843:Chromatin; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D050778:NFATC Transcription Factors; C111652:mariner transposases; D063151:Polycomb Repressive Complex 2; D019895:Transposases