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Figure 1 | Biology Direct

Figure 1

From: Evolution of the RAG1-RAG2 locus: both proteins came from the same transposon

Figure 1

TransibSU transposons in sea urchins and starfish. A: The RAG1-RAG2-like locus in the purple sea urchin genome. DECR (GenBank: XP_793296) and RHPN (GenBank: XP_785878) are neighbor genes flanking the RAG1-RAG2-like locus. Numbers indicate positions of SPRAG1L, SPRAG2L and their flanking genes in Scaffold70 (GenBank: NW_003577031). Scaffold616 (GenBank: NW_003577577) encodes the elongator complex protein 2 gene (Ecp2, conserved in all metazoans). Numbers indicate the beginning and the end of the coding exons (black rectangles) and position of the second intron (between the exons 2 and 3). B: In the green sea urchin L. variegates genome, a unit coding for both LVRAG1L and LVRAG2L is inserted into the second intron of Ecp2, this gene is orthologous to the purple sea urchin Ecp2. Both genomes contain a single copy of the Ecp2 gene. The green sea urchin LVRAG1L/LVRAG2L unit is assembled from two scaffolds. Scaffold positions corresponding to loci coding for Ecp2, LVRAG1L and LVRAG2L are shown above and the green (Scaffold19893) and black (Scaffold71) lines, respectively. The N-terminal part of LVRAG1L is lost (1-272-aa of SPRAG1), the core and C-terminal part is almost intact (it corresponds to pos. 437–978 of SPRAG1; disrupted by one stop codon). The vertical red line indicates the boundary between the LVRAG2L parts (aa positions 1–184 and 185–467), encoded by the two scaffolds due to incomplete assembly. C: The TransibSU transposons in the Bat star genome (Patiria minata, sea star or starfish). One copy of the TransibSU-1_PM transposon can be assembled from three contigs [GenBank: AKZP01053170-AKZP01054172]. The RAG2L protein in this copy was lost due to deletion of a region between the FL1 and FL2 parts (dark blue and brown arrows). The 94% identical copies of FL1 and FL2 constitute the termini of a 3734-bp contig [GenBank: AKZP01064647]. The central part of this contig encodes the PMRAG2L protein. This contig represents a part of the second copy of the TransibSU-1_PM transposon. A copy of the second TransibSU-2_PM transposon is present at the 3’ and 5’ termini of the AKZP01110315 (green line) and AKZP01110316 (blue line) contigs, which are assembled into one scaffold. This transposon is flanked by the CCAGG target site duplication (yellow ovals). Due to the sequencing problems, the internal part of this transposon is not complete. D: Termini of TransibSU, Transibs and V(D)J recombination signal sequences are shown. E: Commonly accepted phylogeny of species colonized by the TransibSU and TransibVDJ transposons. Magenta stars denote the presence of TransibSU transposons and the red stars denote the RAG1-RAG2 locus. The magenta oval indicates an unknown RAG1-RAG2-enocding transposon reported recently as a polymorphic insertion in a lancelet genome [24].

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