Summary auto-generated
This study reports the discovery of a chimeric long terminal repeat (LTR) structure formed by insertion of a HERV-H LTR into the 5' LTR of a HERV-K retroelement in the human genome. The chimera was first identified in chromosome 19p12, a region enriched with zinc finger protein genes, and subsequently detected on chromosomes 10 and Y. Using PCR analysis across primate species, researchers found the chimera in humans, chimpanzees, and gorillas, but not orangutans, indicating the insertion occurred more than 10 million years ago, before divergence of human/chimpanzee and gorilla lineages. Phylogenetic analysis suggests the HERV-H LTR integrated into a pre-existing HERV-K LTR approximately 13-15 million years ago. The chimeric structure creates a novel combination of regulatory modules, with the HERV-K portion containing sequences that bind nuclear proteins and the HERV-H portion containing GC/GT-boxes required for transcriptional activity. This nested integration event exemplifies how human endogenous retroviruses shuffle regulatory modules that may influence expression of neighboring genes.
Key findings
- A chimeric HERV-K–HERV-H LTR was identified on human chromosomes 10, 19, and Y, formed by insertion of a 482 bp HERV-H LTR into the 5' LTR of HERV-K approximately 13-15 million years ago.
- PCR analysis demonstrates the chimera is present in humans, chimpanzees, and gorillas, but absent in orangutans, indicating origin before human-chimpanzee-gorilla divergence (>10 million years ago).
- The chimeric LTR combines regulatory modules from both HERV families, potentially creating new transcriptional regulatory capabilities for nearby genes.
- The chimera is located in a chromosome 19 region enriched with zinc finger protein genes, suggesting functional relevance to gene regulation.
- This LTR-into-LTR integration represents a common mechanism of genome evolution through modular recombination of endogenous retroviral sequences.
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Abstract
A chimeric long terminal repeat (LTR) containing the whole LTR of a human endogenous retrovirus-like element of the H family (HERV-H) inserted downstream of the core enhancer region of the 5' LTR of a HERV- K retroelement was detected and sequenced in the human 19p12 locus, known to be enriched with genes encoding zinc finger proteins. Similar chimeras were also detected in human chromosomes 10 and Y in human- hamster hybrid cells containing individual human chromosomes. This finding was interpreted as evidence of transpositions of the chimera in the genome. PCR analyses detected the chimera in the genomes of chimpanzee and gorilla, but not in that of orangutan. These data demonstrate that the chimera appeared in the primate germ cells more than 10 million years ago, before divergence of the human/chimpanzee and the gorilla lineages. The combination of the two LTRs forms a new regulatory system that can be involved in nearby gene expression.