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Molecular evolution of the human Pgk-2 retroposon.
1Division of Reproductive Biology, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, MD 21205.
Nucleic Acids Research
|February 25, 1990
Summary
The human phosphoglycerate kinase-2 (Pgk-2) gene evolved rapidly from its progenitor, Pgk-1, developing a tissue-specific promoter. This divergence was driven by selection for high-level, cell type-specific expression.
Area of Science:
- Genomics
- Molecular Evolution
- Gene Regulation
Background:
- The human phosphoglycerate kinase (Pgk) gene family comprises Pgk-1, Pgk-2, and a pseudogene (psi hPgk-1).
- Pgk-2 and psi hPgk-1 are intronless retroposons derived from the intron-containing Pgk-1 gene.
Purpose of the Study:
- To compare the evolutionary divergence of Pgk-2 and psi hPgk-1 from Pgk-1.
- To identify nucleotide characteristics distinguishing functional genes.
- To investigate the evolution of Pgk-2's promoter and its relationship with expression levels.
Main Methods:
- Comparative analysis of human and mouse Pgk gene sequences.
- Assessment of nucleotide composition and dinucleotide frequencies.
- Examination of promoter elements and CpG islands.
Main Results:
- Pgk-2 exhibits more rapid evolution than Pgk-1 since their divergence early in mammalian evolution.
- Codon bias in Pgk genes is influenced by dinucleotide composition (deficiency of TA/CG, excess of TG/CT), not solely expression level.
- Evidence supports the hypothesis that Pgk-2 acquired a tissue-specific promoter, involving loss of the Pgk-1 5' CpG island.
Conclusions:
- Selection for high-level, cell type-specific expression drove the divergence of the Pgk-2 retroposon from Pgk-1.
- The evolution of Pgk-2 involved significant changes in its regulatory elements and evolutionary rate.