Characterization of EamaT1, a member of maT family of transposable elements from the earthworm Eisenia andrei (Annelida, Oligochaeta)

Divergent evolution profiles of DD37D and DD39D families of Tc1/mariner transposons in eukaryotes

DNA transposons play a significant role in shaping the size and structure of eukaryotic genomes. The Tc1/mariner transposons are the most diverse and widely distributed superfamily of DNA transposons and the structure and distribution of several Tc1/mariner families, such as DD35E/TR, DD36E/IC, DD37E/TRT, and DD41D/VS, have been well studied. Nonetheless, a greater understanding of the structure and diversity of Tc1/mariner transposons will provide insight into the evolutionary history of eukaryotic genomes. Here, we conducted further analysis of DD37D/maT and DD39D (named Guest, GT), which were identified by the specific catalytic domains DD37D and DD39D. Most transposons of the maT family have a total length of approximately 1.3 kb and harbor a single open reading frame encoding a ~ 346 amino acid (range 302-398 aa) transposase protein, flanked by short terminal inverted repeats (TIRs) (13-48 base pairs, bp). In contrast, GTs transposons were longer (2.0-5.8 kb), encoded a transposase protein of ~400 aa (range 140-592 aa), and were flanked by short TIRs (19-41 bp). Several conserved motifs, including two helix-turn-helix (HTH) motifs, a GRPR (GRKR) motif, a nuclear localization sequence, and a DDD domain, were also identified in maT and GT transposases. Phylogenetic analyses of the DDD domain showed that the maT and GT families each belong to a monophyletic clade and appear to be closely related to DD41D/VS and DD34D/mariner. In addition, maTs are mainly distributed in invertebrates (144 species), whereas GTs are mainly distributed in land plants through a small number of GTs are present in Chromista and animals. Sequence identity and phylogenetic analysis revealed that horizontal transfer (HT) events of maT and GT might occur between kingdoms and phyla of eukaryotes; however, pairwise distance comparisons between host genes and transposons indicated that HT events involving maTs might be less frequent between invertebrate species and HT events involving GTs may be less frequent between land plant species. Overall, the DD37D/maT and DD39D/GT families display significantly different distribution and tend to be identified in more ancient evolutionary families. The discovery of intact transposases, perfect TIRs, and target site duplications (TSD) of maTs and GTs illustrates that the DD37D/maT and DD39D/GT families may be active. Together, these findings improve our understanding of the diversity of Tc1/mariner transposons and their impact on eukaryotic genome evolution.

Twist promotes tumor metastasis in basal-like breast cancer by transcriptionally upregulating ROR1

Rationale: Twist is a key transcription factor for induction of epithelial-mesenchymal transition (EMT), which promotes cell migration, invasion, and cancer metastasis, confers cancer cells with stem cell-like characteristics, and provides therapeutic resistance. However, the functional roles and targeted genes of Twist in EMT and cancer progression remain elusive. Methods: The potential targeted genes of Twist were identified from the global transcriptomes of T47D/Twist cells by microarray analysis. EMT phenotype was detected by western blotting and immunofluorescence of marker proteins. The dual-luciferase reporter and chromatin immunoprecipitation assays were employed to observe the direct transcriptional induction of ROR1 by Twist. A lung metastasis model was used to study the pro-metastatic role of Twist and ROR1 by injecting MDA-MB-231 cells into tail vein of nude mice. Bio-informatics analysis was utilized to measure the metastasis-free survival of breast cancer patients. Results: Twist protein was proved to directly activate the transcription of ROR1 gene, a receptor of Wnt5a in non-canonical WNT signaling pathway. Silencing of ROR1 inhibited EMT process, cell migration, invasion, and cancer metastasis of basal-like breast cancer (BLBC) cells. Knockdown of ROR1 also ameliorated the pro-metastatic effect of Twist. Furthermore, analyses of clinical specimens indicated that high expression of both ROR1 and Twist tightly correlates with poor metastasis-free survival of breast cancer patients. Conclusion: ROR1 is a targeted gene of Twist. Twist/ROR1 signaling is critical for invasion and metastasis of BLBC cells.

The Tol1 element of the medaka fish, a member of the hAT transposable element family, jumps in Caenorhabditis elegans

Tol1 is a DNA-based transposable element residing in the genome of the medaka fish Oryzias latipes, and has been proven to be transposed in various vertebrate species, including mammals. This element belongs to the hAT (hobo/Activator/Tam3) transposable element family, whose members are distributed in a wide range of organisms. It is thus possible that Tol1 is mobile in organisms other than vertebrates. We here show that transposition of this element occurs in the nematode Caenorhabditis elegans. A donor plasmid containing a Tol1 element and a helper plasmid carrying the transposase gene were delivered into gonad cells and, after several generations of culturing, were recovered from worms. PCR analysis of the donor plasmid, using primers that encompassed the Tol1 element, revealed excision of the Tol1 portion from the plasmid. Analysis of genomic DNA of the worms by the inverse PCR method provided evidence that Tol1 had been integrated into the C. elegans chromosomes. Vertebrates and C. elegans are phylogenetically distantly related organisms in that the former are deuterostomes and the latter a protostome animal. Our results indicate (1) the transposition reaction of the Tol1 element requires, besides the transposase, no factors from host cells, or (2) the host factors, even if required, are those that are common to protostomes and deuterostomes. The results also have significance for the development of a gene transfer vector and other biotechnology tools for C. elegans.