A transpoviron is a
plasmid
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; howev ...
-like
genetic element found in the
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...
s of
giant DNA viruses.
They are linear
DNA elements of approximately 7 kilobases that encompass six to eight
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...
encoding
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s. Two of these genes are homologous to
virophage
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for ...
genes. Transpovirons encode a superfamily 1
helicase
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separat ...
, which encompasses an inactivated family B DNA polymerase domain.
Homologs of this unique polymerase-helicase fusion protein are widespread in
Polinton Polintons (also called Mavericks) are large DNA transposons which contain genes with homology to viral proteins and which are often found in eukaryotic genomes. They were first discovered in the mid-2000s and are the largest and most complex know ...
-Like Viruses (PLV).
Based on the phylogenetic analysis of the helicase domain the discoverers of PLVs concluded that transpovirons evolved from PLV via the loss of several genes including those encoding the morphogenetic module proteins.
References
{{Organisms et al.
Mobile genetic elements