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Characterization of telomeric single-stranded 3' overhangs and t-circles in Naumovozyma castellii

Garibo Domingo, Teresa (2022) MOBN03 20212
Degree Projects in Molecular Biology
Popular Abstract
Telomeres, the guardians of the chromosomes

Telomeres are structures found at the end of eukaryotic chromosomes. They are composed of a repetitive DNA sequence and proteins, and their main function is to protect the chromosome ends. In human somatic cells telomeres shorten with each cell division, acting as a biological clock of cell aging. However, cancer cells are able to divide infinitely by reactivating the mechanism of telomere elongation. Unraveling the molecular mechanisms of telomere elongation would help develop new approaches to fight cancer.

Yeast has been an organism widely used in the study of telomeres because of its highly active telomerase, the enzyme in charge of lengthening the telomeres. This enzyme binds to the... (More)
Telomeres, the guardians of the chromosomes

Telomeres are structures found at the end of eukaryotic chromosomes. They are composed of a repetitive DNA sequence and proteins, and their main function is to protect the chromosome ends. In human somatic cells telomeres shorten with each cell division, acting as a biological clock of cell aging. However, cancer cells are able to divide infinitely by reactivating the mechanism of telomere elongation. Unraveling the molecular mechanisms of telomere elongation would help develop new approaches to fight cancer.

Yeast has been an organism widely used in the study of telomeres because of its highly active telomerase, the enzyme in charge of lengthening the telomeres. This enzyme binds to the single-stranded 3’ region at the end of the telomeres to synthetize new telomeric DNA. The goal of this project was to study the length dynamics of these single-stranded 3’ overhangs in the budding yeast Naumovozyma castellii.

To study the 3’ overhangs we used the DSN assay, where an enzyme digests the double-stranded sequence of the DNA without affecting the single-stranded overhang. We were able to describe for the first time how N. castellii cells accumulate a specific set of long 3’ overhangs while they are actively growing. Interestingly, the accumulation of long overhangs was found in cells with an active telomerase, as well as in cells with a non-functional telomerase. This means that having long overhangs could have some biological relevance in the protection of the telomeric ends.

Another aspect we were interested in was how yeast cells are able to elongate their telomeres without an active telomerase. T-circles are DNA circles containing telomeric sequences. They have been proposed to be involved in telomere elongation in the absence of telomerase, and they have already been identified as a hallmark of cancer cells and some telomerase-deficient yeast cells. We developed a method called the Rolling Circle Amplification (RCA) assay to study the presence of these molecules in N. castellii. It relies in the ability of a polymerase enzyme to amplify circular DNA molecules, like t-circles. Our preliminary results suggest that N. castellii cells may contain telomeric DNA circles. This was the first step to start off the study of t-circles in N. castellii and their possible implication in the elongation of telomeres.





Master’s Degree Project in Molecular Biology 60 credits 2022
Department of Biology, Lund University

Advisor: Marita Cohn
Molecular Genetics, Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Garibo Domingo, Teresa
supervisor
organization
course
MOBN03 20212
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9113768
date added to LUP
2023-04-26 14:47:58
date last changed
2023-04-26 14:47:58
@misc{9113768,
  author       = {{Garibo Domingo, Teresa}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Characterization of telomeric single-stranded 3' overhangs and t-circles in Naumovozyma castellii}},
  year         = {{2022}},
}