Molecular evolution of the second ancient human mariner transposon, Hsmar2, illustrates patterns of neutral evolution in the human genome lineage

Hugh M. Robertson, Rebecca Martos

Research output: Contribution to journalArticlepeer-review

Abstract

A consensus sequence for the second ancient mariner identified in the human genome, Hsmar2, was constructed by majority rule from full-length and partial sequences of 44 of the ±1000 copies in the genome. This 1300 base pair (bp) consensus has 31 bp imperfect terminal repeats (ITRs) and encodes a 351 amino acid (aa) mariner transposase. The sequence of this transposase has allowed classification of Hsmar2 as a basal lineage of the irritans subfamily of mariners, sharing at most 38% aa identity with other members of the subfamily. The individual copies in the human genome are all highly mutated from the consensus, having suffered numerous small and some large insertions and deletions (indels), including many insertions of S and J subfamily Alu elements. The copies differ, on average, from the consensus by 11.6%, have suffered 11.8 indels per kilobase (kb), and only 3.7% of the 30 hypermutable CpG dinucleotide pairs in the consensus remain intact. This level of divergence indicates that the ancestrally active Hsmar2 element represented by the consensus was present in the human genome lineage about 80 million years (Myr) ago. Each copy has apparently evolved since then largely independently of the others, and with little constraint on its transposase coding capacity. This pattern of molecular evolution fits the current model for mariner transposon evolution. These copies provide multiple independent datasets for evaluating the pattern of neutral evolution in the human genome, for example, they confirm that most indels are very short and that deletions are twice as common as insertions.

Original languageEnglish (US)
Pages (from-to)219-228
Number of pages10
JournalGene
Volume205
Issue number1-2
DOIs
StatePublished - Dec 31 1997

Keywords

  • Consensus sequence
  • D,D35E motif
  • DNA sequence analysis
  • Phylogenetic analysis
  • Star phylogeny
  • mariner transposase

ASJC Scopus subject areas

  • Genetics

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