A novel repeated element with Z-DNA-forming potential is widely found in evolutionarily diverse eukaryotic genomes.

TLDR

The authors used Southern blotting with 32P‑labeled poly(dT‑dG) and poly(dG‑dC) probes to survey eukaryotic genomes for Z‑DNA‑forming sequences. They found that dT‑dG alternating sequences, capable of forming Z‑DNA, are ubiquitous and evolutionarily conserved—from ~100 copies in yeast to tens of thousands in higher eukaryotes—while dC‑dG alternating sequences are moderately repetitive in mammals but absent in yeast and calf, highlighting the widespread abundance of potential Z‑DNA‑forming elements.

Abstract

By Southern blotting and hybridization analysis using 32P-labeled poly(dT-dG) . poly(dC-dA) as a probe, we have found, in eukaryotic genomes, a huge number of stretches of dT-dG alternating sequence, a sequence that has been shown to adopt the Z-DNA conformation under some conditions. This sequence was found in all eukaryotic genomes examined from yeast to human, indicating extraordinary evolutionary conservation. The number of the sequence ranged from about 100 in yeast to tens of thousands in higher eukaryotes. Comparison of nucleotide sequences of dT-dG alternating regions and its flanking regions in several cloned genes showed that the repeated element [the Z(T-G) element]] consists only of dT-dG alternating sequence with variable length. The presence of another purine-pyrimidine alternating sequence was also surveyed in eukaryotic genomes by Southern blot hybridization using 32P-labeled poly(dG-dC) . poly(dG-dC) as the probe. The stretches of dC-dG alternating sequence [the Z(C-G) element] were found to be moderately repetitive in human, mouse, and salmon genomes. However, a few and no copies of the Z(C-G) element were found in yeast and calf genomes, respectively. These results provide evidence for the abundance of potential Z-DNA-forming sequences in nature.