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TCAGG, an alternative telomeric sequence in insects.

Brankica Mravinac1, Nevenka Meštrović, Vladimir Vanja Cavrak

  • 1Division of Molecular Biology, Ruđer Bošković Institute, Bijenička, Zagreb, Croatia. Brankica.Mravinac@irb.hr

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|April 19, 2011
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Summary

The canonical insect telomere sequence (TTAGG)n is replaced by (TCAGG)n in the Tenebrionoidea beetle superfamily. Not all beetles use these sequences, indicating diverse telomere structures and maintenance in Coleoptera.

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Area of Science:

  • Genetics
  • Molecular Biology
  • Evolutionary Biology

Background:

  • The TTAGG repeat is considered the canonical telomere sequence in Insecta.
  • Telomeres protect chromosome ends and are maintained by telomerase.

Purpose of the Study:

  • To investigate the diversity of telomeric DNA sequences in Coleoptera.
  • To identify alternative telomeric motifs beyond the TTAGG repeat.

Main Methods:

  • Southern hybridization
  • BAL 31 DNA end-degradation assay
  • Fluorescence in situ hybridization (FISH)

Main Results:

  • (TCAGG)n repeats were found to substitute for (TTAGG)n in all tested species of the Tenebrionoidea superfamily.
  • Experimental evidence confirmed (TCAGG)n repeats as terminal sequences on Tribolium castaneum chromosomes.
  • Species lacking both TTAGG and TCAGG repeats were identified, indicating non-ubiquitous distribution of these motifs.
  • Timarcha balearica harbors (TTAGG)n repeats at non-telomeric positions, adding complexity to insect telomere biology.
  • Other sequence variants (CTAGG, CTGGG, TTGGG, TTAGGG) were ruled out as replacements.

Conclusions:

  • The (TCAGG)n repeat represents the first identified alternative to TTAGG-type telomeres in insects.
  • Telomeric sequences and maintenance mechanisms in Coleoptera are more diverse than previously thought.
  • Further research is needed to elucidate the telomeric sequences and mechanisms in species lacking TTAGG and TCAGG repeats.