Repetitive DNA in search of a function - a study of telomeric and centromeric sequences in Chironomus

Research output: ThesisDoctoral Thesis (compilation)

Abstract

Repetitive DNA is quantitatively the main component of telomeres and centromeres, structures responsible for maintenance of the eukaryotic chromosome. The telomere is the specialized nucleoprotein complex that terminates linear chromosomes. In most species the DNA component consists of short repeats which are generated by the enzyme complex telomerase. However, there are important exceptions such as the Drosophila melanogaster telomeres which are elongated by retrotransposons and, as documented in the present thesis, a third telomeric system in Chironomus pallidivittatus in the form of arrays of 340 bp long complex tandem repeats which extend to the end of their chromosomes. Complex repeats are not elongated by telomerase and one aim of my work has therefore been to elucidate possible regeneration mechanisms for telomeres with such repeats. I have obtained evidence for DNA increase through DNA sequences of nontelomeric origin being inserted into the telomeric repeat array via gene conversion. Immunolocalization of reverse transcriptase related proteins in the telomeric puff of the related species C. thummi revealed, on the other hand, a possible link between the regeneration of Chironomus telomeric complex repeats and mechanisms used by other eukaryotes. Only seven of the eight pairs of chromosome termini in C. pallidivittatus have 340 bp repeats. The remaining telocentric end contains another repeat, the centromeric 155 bp unit, probably extending to the chromosome end. In the arrays of this repeat, a putative homologue of the mammalian centromeric CENP-B box has been found and characterized. Its interspersed distribution and its surrounding direct repeats suggest a mobile origin. It is present in different recombined forms, which could be related to a role in recombination as has been suggested for the human CENP-B box.

Details

Authors
  • Casimiro Castillejo-Lopez
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Genetics

Keywords

  • Chironomus, CENP-B box, mobile elements, reverse transcriptase, gene conversion, satellite, repetitive DNA, Telomere, centromere, Genetics, cytogenetics, Genetik, cytogenetik
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
  • [unknown], [unknown], Supervisor, External person
Award date1998 Oct 28
Publisher
  • Department of Genetics, Lund University
Publication statusPublished - 1998
Publication categoryResearch

Bibliographic note

Defence details Date: 1998-10-28 Time: 10:15 Place: Geniska inst. Lund External reviewer(s) Name: Landegren, Ulf Title: Prof Affiliation: Dept. of medical genetics. Uppsala. Sweden --- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Genetics (Closed 2011) (011005100), Invertebral Developmental Biology, Udo Haecker's group (013212048)