Long Non-coding RNAs in the Human Genome Acquired by Horizontal Gene Transfer

Horizontal gene transfer of mobile genetic elements is an essential component of prokaryotic evolution. These insertion events in eukaryotes and particularly in the human genome have been investigated by various methodologies with varying results. In this paper, we implement a sequence composition approach to investigate insertions of genomic islands in the human genome. A modified version of a prokaryotic GI identifier, SeqWord Gene Island Sniffer v.2.0, was used to predict genomic islands in the hg38 version of the human genome. Predicted genomic islands were enriched with long non-coding RNAs and also contributed to the acquisition and modification of proteins associated with the immune system and gonad development, albeit to a lesser extent. The estimated rate of acquisition of these genomic islands in vertebrate genomes was non-linear with regards to species divergence times with an acceleration at the time of vertebrate land invasion and during the transition of prosimians to monkeys soon after the Cretaceous-Paleogene extinction. The rapid acquisition of non-conserved long non-coding RNAs in the human genome and probably in vertebrata genomes was facilitated by horizontal gene transfer. All predicted human genomic islands and supporting information are freely accessible from http://hislands.bi.up.ac.za.