Robust Binding Capability and Occasional Gene Loss of Telomere-Binding Proteins Underlying Telomere Evolution in Nematoda.

Telomeres, the nucleoprotein complexes that protect the ends of linear chromosomes, are essential for maintaining the stability of eukaryotic genomes. As telomeres generally consist of repetitive DNA associated with specifically bound proteins, telomeric repeat motifs are thought to be difficult to evolve. However, a recent study identified nematodes with telomeric repeats distinct from the canonical TTAGGC motif. Here, we investigated how telomere repeats could have evolved despite the challenge posed by the specificity of telomere-binding proteins (TBPs) to the telomeric DNA in Nematoda. We performed a phylogenetic analysis and electrophoresis mobility shift assays to assess the binding affinities of two TBPs, which displayed different conservation patterns. Our results revealed that the well-conserved protein CEH-37 exhibits limited specificity, unable to distinguish telomeric repeats found in nematodes except for the TTAGGG motif, while the less conserved POT proteins displayed rigid specificity. These findings suggest that the emergence of novel telomeric repeat motifs correlated with the characteristics and evolutionary outcomes of TBPs in Nematoda. Our study not only revealed the dynamics of telomere evolution but also enhanced the understanding of the evolutionary relationship between proteins and DNAs.