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Viruses. 2017 Apr 11;9(4). pii: E78. doi: 10.3390/v9040078.

LTR-Retrotransposons from Bdelloid Rotifers Capture Additional ORFs Shared between Highly Diverse Retroelement Types.

Author information

1
Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA. frodriguez@mbl.edu.
2
Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA. awkenefick@ucdavis.edu.
3
Present address: UC Davis Genome Center-GBSF, University of California, Davis, CA 95616, USA. awkenefick@ucdavis.edu.
4
Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA. iarkhipova@mbl.edu.

Abstract

Rotifers of the class Bdelloidea, microscopic freshwater invertebrates, possess a highlydiversified repertoire of transposon families, which, however, occupy less than 4% of genomic DNA in the sequenced representative Adineta vaga. We performed a comprehensive analysis of A. vaga retroelements, and found that bdelloid long terminal repeat (LTR)retrotransposons, in addition to conserved open reading frame (ORF) 1 and ORF2 corresponding to gag and pol genes, code for an unusually high variety of ORF3 sequences. Retrovirus-like LTR families in A. vaga belong to four major lineages, three of which are rotiferspecific and encode a dUTPase domain. However only one lineage contains a canonical envlike fusion glycoprotein acquired from paramyxoviruses (non-segmented negative-strand RNA viruses), although smaller ORFs with transmembrane domains may perform similar roles. A different ORF3 type encodes a GDSL esterase/lipase, which was previously identified as ORF1 in several clades of non-LTR retrotransposons, and implicated in membrane targeting. Yet another ORF3 type appears in unrelated LTR-retrotransposon lineages, and displays strong homology to DEDDy-type exonucleases involved in 3'-end processing of RNA and single-stranded DNA. Unexpectedly, each of the enzymatic ORF3s is also associated with different subsets of Penelope-like Athena retroelement families. The unusual association of the same ORF types with retroelements from different classes reflects their modular structure with a high degree of flexibility, and points to gene sharing between different groups of retroelements.

KEYWORDS:

DEDDy exonuclease; GDSL esterase; dUTPase; envelope gene (ENV); retrovirus-like transposable elements

PMID:
28398238
PMCID:
PMC5408684
DOI:
10.3390/v9040078
[Indexed for MEDLINE]
Free PMC Article

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