title: Homologues of bacterial TnpB_IS605 are widespread in diverse eukaryotic transposable elements.
abstract: BACKGROUND
  Bacterial insertion sequences (IS) of IS200/IS605 and IS607 family often encode a transposase (TnpA) and a protein of unknown function, TnpB.
  
  
  RESULTS
  Here we report two groups of TnpB-like proteins (Fanzor1 and Fanzor2) that are widespread in diverse eukaryotic transposable elements (TEs), and in large double-stranded DNA (dsDNA) viruses infecting eukaryotes. Fanzor and TnpB proteins share the same conserved amino acid motif in their C-terminal half regions: D-X(125, 275)-[TS]-[TS]-X-X-[C4 zinc finger]-X(5,50)-RD, but are highly variable in their N-terminal regions. Fanzor1 proteins are frequently captured by DNA transposons from different superfamilies including Helitron, Mariner, IS4-like, Sola and MuDr. In contrast, Fanzor2 proteins appear only in some IS607-type elements. We also analyze a new Helitron2 group from the Helitron superfamily, which contains elements with hairpin structures on both ends. Non-autonomous Helitron2 elements (CRe-1, 2, 3) in the genome of green alga Chlamydomonas reinhardtii are flanked by target site duplications (TSDs) of variable length (approximately 7 to 19 bp).
  
  
  CONCLUSIONS
  The phylogeny and distribution of the TnpB/Fanzor proteins indicate that they may be disseminated among eukaryotic species by viruses. We hypothesize that TnpB/Fanzor proteins may act as methyltransferases.
authors.affiliation: Genetic Information Research Institute, 1925 Landings Drive, Mountain View, CA, 94043, USA. jurka@girinst.org.
authors.forename: Weidong
authors.initials: W
authors.lastname: Bao
authors.forename: Jerzy
authors.initials: J
authors.lastname: Jurka
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