Factors acting on Mos1 transposition efficiency

<p>Abstract</p> <p>Background</p> <p><it>Mariner-</it>like elements (<it>MLEs</it>) are widespread DNA transposons in animal genomes. Although <it>in vitro </it>transposition reactions require only the transposase, various factors depending on the host, the physico-chemical environment and the transposon sequence can interfere with the <it>MLEs </it>transposition <it>in vivo</it>.</p> <p>Results</p> <p>The transposition of <it>Mos1</it>, first isolated from <it>drosophila mauritiana</it>, depends of both the nucleic acid sequence of the DNA stuffer (in terms of GC content), and its length. We provide the first <it>in vitro </it>experimental demonstration that MITEs of <it>MLE </it>origin, as small as 80 to 120-bp, are able to transpose. Excessive temperature down-regulates <it>Mos1 </it>transposition, yielding excision products unable to re-integrate. Finally, the super-helicity of the DNA transposon donor has a dramatic impact on the transposition efficiency.</p> <p>Conclusion</p> <p>The study highlights how experimental conditions can bias interpretation of <it>mariner </it>excision frequency and quality. <it>In vitro</it>, the auto-integration pathway markedly limits transposition efficiency to new target sites, and this phenomenon may also limit events in the natural host. We propose a model for small transposons transposition that bypasses DNA bending constraints.</p

SETMAR, a case of primate co-opted genes: towards new perspectives

International audienceAbstract Background We carry out a review of the history and biological activities of one domesticated gene in higher primates, SETMAR, by discussing current controversies. Our purpose is to open a new outlook that will serve as a framework for future work about SETMAR, possibly in the field of cognition development. Main body What is newly important about SETMAR can be summarized as follows: (1) the whole protein sequence is under strong purifying pressure; (2) its role is to strengthen existing biological functions rather than to provide new ones; (3) it displays a tissue-specific pattern of expression, at least for the alternative-splicing it undergoes. Studies reported here demonstrate that SETMAR protein(s) may be involved in essential networks regulating replication, transcription and translation. Moreover, during embryogenesis, SETMAR appears to contribute to brain development. Short conclusion Our review underlines for the first time that SETMAR directly interacts with genes involved in brain functions related to vocalization and vocal learning. These findings pave the way for future works regarding SETMAR and the development of cognitive abilities in higher primates

Assembly of the mariner Mos1 Synaptic Complex

The mobility of transposable elements via a cut-and-paste mechanism depends on the elaboration of a nucleoprotein complex known as the synaptic complex. We show here that the Mos1 synaptic complex consists of the two inverted terminal repeats of the element brought together by a transposase tetramer and is designated paired-end complex 2 (PEC2). The assembly of PEC2 requires the formation of a simpler complex, containing one terminal repeat and two transposase molecules and designated single-end complex 2 (SEC2). In light of the formation of SEC2 and PEC2, we demonstrate the presence of two binding sites for the transposase within a single terminal repeat. We have found that the sequence of the Mos1 inverted terminal repeats contains overlapping palindromic and mirror motifs, which could account for the binding of two transposase molecules “side by side” on the same inverted terminal repeat. We provide data indicating that the Mos1 transposase dimer is formed within a single terminal repeat through a cooperative pathway. Finally, the concept of a tetrameric synaptic complex may simply account for the inability of a single mariner transposase molecule to interact at the same time with two kinds of DNA: the inverted repeat and the target DNA

Regulation of mariner transposition: the peculiar case of Mos1.

BACKGROUND: Mariner elements represent the most successful family of autonomous DNA transposons, being present in various plant and animal genomes, including humans. The introduction and co-evolution of mariners within host genomes imply a strict regulation of the transposon activity. Biochemical data accumulated during the past decade have led to a convergent picture of the transposition cycle of mariner elements, suggesting that mariner transposition does not rely on host-specific factors. This model does not account for differences of transposition efficiency in human cells between mariners. We thus wondered whether apparent similarities in transposition cycle could hide differences in the intrinsic parameters that control mariner transposition. PRINCIPAL FINDINGS: We find that Mos1 transposase concentrations in excess to the Mos1 ends prevent the paired-end complex assembly. However, we observe that Mos1 transposition is not impaired by transposase high concentration, dismissing the idea that transposase over production plays an obligatory role in the down-regulation of mariner transposition. Our main finding is that the paired-end complex is formed in a cooperative way, regardless of the transposase concentration. We also show that an element framed by two identical ITRs (Inverted Terminal Repeats) is more efficient in driving transposition than an element framed by two different ITRs (i.e. the natural Mos1 copy), the latter being more sensitive to transposase concentration variations. Finally, we show that the current Mos1 ITRs correspond to the ancestral ones. CONCLUSIONS: We provide new insights on intrinsic properties supporting the self-regulation of the Mos1 element. These properties (transposase specific activity, aggregation, ITR sequences, transposase concentration/transposon copy number ratio...) could have played a role in the dynamics of host-genomes invasion by Mos1, accounting (at least in part) for the current low copy number of Mos1 within host genomes

SETMAR Shorter Isoform: A New Prognostic Factor in Glioblastoma

International audienceRecent evidence suggests that the chimeric protein SETMAR is a factor of interest in cancer, especially in glioblastoma. However, little is known about the expression of this protein in glioblastoma tissues, and no study has been done to assess if SETMAR could be a prognostic and/or diagnostic marker of glioblastoma. We analyzed protein extracts of 47 glioblastoma samples coming from a local and a national cohort of patients. From the local cohort, we obtained localized biopsies from the central necrosis area, the tumor, and the perilesional brain. From the French Glioblastoma Biobank (FGB), we obtained three types of samples: from the same tumors before and after treatment, from long survivors, and from very short survivors. We studied the correlations between SETMAR amounts, clinical profiles of patients and other associated proteins (PTN, snRNP70 and OLIG2). In glioblastoma tissues, the shorter isoform of SETMAR (S-SETMAR) was predominant over the full-length isoform (FL-SETMAR), and the expression of both SETMAR variants was higher in the tumor compared to the perilesional tissues. Data from the FGB showed that SETMAR amounts were not different between the initial tumors and tumor relapses after treatment. These data also showed a trend toward higher amounts of S-SETMAR in long survivors. In localized biopsies, we found a positive correlation between good prognosis and large amounts of S-SETMAR in the perilesional area. This is the main result presented here: survival in Glioblastoma is correlated with amounts of S-SETMAR in perilesional brain, which should be considered as a new relevant prognosis marker

Characterization of Mcmar1, a mariner-like element with large inverted terminal repeats (ITRs) from the phytoparasitic nematode Meloidogyne chitwoodi

International audienceTwo copies of a new mariner-like element (MLE) presenting unusual inverted terminal repeats (ITRs), Mcmar1-2 and Mcmar1-2, were cloned and sequenced in the genome of the phytoparasitic nematode Meloidogyne chitwoodi. Although the sequence features of these Mcmar1 transposons are commonplace and link them to the mariner family, at their extremities they have large 355-pb long inverted terminal repeats that are perfectly conserved. This characteristic distinguishes them from all the other MLEs so far described that have imperfectly conserved ITRs of about 26-30 bp. In consequence, the sequenced full-length Mcmar1-1 element is 2000 bp long, and comprises an uninterrupted open reading frame (ORF) that encodes a putatively active transposase with 340 amino acid residues. The Mcmar1-2 element is a deleted form of Mcmar1-1 that contains a deletion overlapping most of the internal region of the 5'ITR and the 5' region of the transposase ORF. The presence of large ITRs in different transposons related to the Tc1-mariner super-family is discussed