First identification of telomeric DNA sequences in Trichomonas vaginalis

Trichomoniasis is the most common nonviral sexually transmitted disease; it is caused by Trichomonas vaginalis and seriously threatens human reproductive health. Telomeres are specialised DNA-protein complexes at the ends of chromosomes that have a protective function. The aim of the present study was to identify and characterise the telomeric DNA of T. vaginalis-which has not been previously reported-by multiple molecular methods including sequencing, the Bal nuclease (BAL) 31 nuclease assay, fluorescence in situ hybridisation (FISH), and Southern blotting. We found numerous repeated units of TTTTAGGG in T. vaginalis genomic DNA digested with S1 nuclease in combination with XbaI restriction enzyme. The (TTTTAGGG)_n tandem repeats were also highly sensitive to BAL 31 exonuclease digestion. We confirmed that the (TTTTAGGG)_n repeats were located at the end of T. vaginalis chromosomes by FISH. Restriction enzyme digestion combined with Southern blotting using a digoxigenin-labelled (TTTTAGGG)₅ probe showed that the T. vaginalis telomeric DNA length varied from 1.0 to 1.5 kb. This is the first report on the telomeric DNA sequence of T. vaginalis which includes the length and distribution on chromosomes; our findings lay a foundation for further study on telomere maintenance mechanisms in T. vaginalis.