Recombinant SINEs are formed at high frequency during induced retrotransposition in vivo

Abstract

non-long terminal repeat Retrotransposons are referred to as long interspersed nuclear elements (LInEs) and their non-autonomous partners are short interspersed nuclear elements (sInEs). It is believed that an active sInE copy, upon retrotransposition, generates near identical copies of itself, which subsequently accumulate mutations resulting in sequence polymorphism. Here we show that when a retrotransposition-competent cell line of the parasitic protist Entamoeba histolytica, transfected with a marked sInE copy, is induced to retrotranspose, > 20% of the newly retrotransposed copies are neither identical to the marked sInE nor to the mobilized resident sInEs. Rather they are recombinants of resident sInEs and the marked sInE. They are a consequence of retrotransposition and not DnA recombination, as they are absent in cells not expressing the retrotransposition functions. This high-frequency recombination provides a new explanation for the existence of mosaic sInEs, which may impact on genetic analysis of sInE lineages, and measurement of phylogenetic distances.

Stress granule formation inEntamoeba histolytica: cross-talk between EhMLBP, EhRLE3 reverse transcriptase and polyubiquitinated proteins

“…A). We also observed that the accumulation of EN transcripts (Yadav et al ., ) did not promote the formation of these EhMLBP‐containing granules (data not shown).…”

“…Close examination of this sequence indicates the presence of seven point mutations (in particular C to T mutations) that are most likely resulted from deamination of methylated cytosines (Harony et al, 2006b). These mutations are stop codon mutations that impair the translation of the mRNA into a functional RT (Yadav et al, 2012). The N-terminus region of EhRLE3 was cloned downstream to the promoter of the ribosomal protein RP-L21 (Ehg34) in the sense and antisense orientation in order to generate the plasmids, pSE-EhRLE3 and pAS-EhRLE3 respectively (Fig.…”

“…EhLINE 3 is devoid of ORF-1 (Bakre et al, 2005). These LINEs are inactive due to the accumulation of numerous mutations (Harony et al, 2006a;Yadav et al, 2012). However, their past functionality was demonstrated by reconstructing an active LINE from constituents of mutated LINEs (Yadav et al, 2012).…”

Homologous Recombination Occurs in Entamoeba and Is Enhanced during Growth Stress and Stage Conversion

“…E. histolytica harbours a large number of non-LTR retrotransposons, which are distributed on all chromosomes, and account for ∼11% of the genome [53], [55], [62]. Active retrotransposition has recently been demonstrated in an E. histolytica cell line [63]. Although circumstantial, this further suggests that Entamoeba might engage in sexual exchange of DNA sequences at some stage in their life cycle.…”

Genomic distribution of SINEs in Entamoeba histolytica strains: implication for genotyping

“…This can be inferred from the fact that most genomic copies of the EhLINE1 retrotransposon (which provides the machinery for EhSINE1 mobilization through retrotransposition) are inactive. We have shown experimentally that the retrotransposition activity in these cells is very low or absent [39]. Therefore the genomic location of SINEs in a given strain is stable enough to be used as a strain-specific signature.…”