{"id":{"repo_id":"toronto-retro","oai_identifier":"oai:utoronto.scholaris.ca:1807/121518"},"canonical_url":"https://search.dev.ndltd.org/etd/toronto-retro/oai:utoronto.scholaris.ca:1807/121518","repository":{"repo_id":"toronto-retro","name":"University of Toronto","base_url":"https://utoronto.scholaris.ca/server/oai/request"},"display":{"title":"RNA-binding Proteins and RNA-DNA Hybrids Regulate Repetitive DNA Stability in Health and Disease","abstract":"The preservation of genome stability is essential to proper cellular function. Repetitive DNA sequences, such as the ribosomal DNA repeats (rDNA) and transposons, represent a large portion of eukaryotic genomes. Due to their repetitive nature, these loci are prone to aberrant recombination. In fact, rDNA repeat instability and increased transposon activity are hallmarks of neurodegenerative disease. Thus, cells employ multiple mechanisms to safeguard the integrity of repetitive loci. The RNA-binding protein Ataxin-2 (Pbp1 in yeast) regulates the stability of rDNA and yeast Ty1 retrotransposons. Interestingly, the human protein (ATXN2) undergoes trinucleotide repeat expansion in the neurodegenerative diseases spinocerebellar ataxia type II (SCA2) and amyotrophic lateral sclerosis. Here, we create yeast models of Ataxin-2-linked neurodegeneration. SCA2-modeling cells exhibit Ty1 protein aggregates, which aberrantly localize to the nucleolus and hyperactivate the degradation of non-coding RNAs transcribed from the intergenic spacer of the rDNA repeats. This induces rDNA recombination and premature aging. Thus, our yeast models suggest trinucleotide repeat expansion of Ataxin-2 represents a gain-of-function mutation that may trigger neurodegeneration through alterations to the stability of repetitive DNA, uniting the “rDNA instability” and “protein aggregation” theories of aging. In addition, we discover a new mechanism that drives the mobility of retrotransposons via RNA-DNA hybrids. RNA-DNA hybrids are duplex nucleic acid structures that form when an RNA molecule binds to its DNA template. RNA-DNA hybrids can generate a tri-nucleic acid structure known as an R-loop that is composed of the RNA-DNA hybrid and a displaced single-stranded non-template DNA. We find that RNA-DNA hybrid structures and R-loops can form on extra-chromosomal Ty1 cDNA in yeast, but these structures drive Ty1 retromobility through distinct mechanisms. Ty1-associated R-loops drive retromobility through the canonical integration pathway, while Ty1-associated RNA-cDNA hybrids drive retromobility through a non-canonical homologous recombination-dependent pathway. Thus, the structure of an RNA-DNA hybrid (duplex versus triplex) may help dictate the mechanism through which it mobilizes transposable elements. Taken together, our yeast genetic studies reveal how intergenic non-coding RNAs and protein aggregates associated with repetitive DNA loci may collaboratively drive neurodegeneration and how RNA-DNA hybrids and R-loops differentially contribute to the mobilization of transposable elements.","abstract_html":"The preservation of genome stability is essential to proper cellular function. Repetitive DNA sequences, such as the ribosomal DNA repeats (rDNA) and transposons, represent a large portion of eukaryotic genomes. Due to their repetitive nature, these loci are prone to aberrant recombination. In fact, rDNA repeat instability and increased transposon activity are hallmarks of neurodegenerative disease. Thus, cells employ multiple mechanisms to safeguard the integrity of repetitive loci. The RNA-binding protein Ataxin-2 (Pbp1 in yeast) regulates the stability of rDNA and yeast Ty1 retrotransposons. Interestingly, the human protein (ATXN2) undergoes trinucleotide repeat expansion in the neurodegenerative diseases spinocerebellar ataxia type II (SCA2) and amyotrophic lateral sclerosis. Here, we create yeast models of Ataxin-2-linked neurodegeneration. SCA2-modeling cells exhibit Ty1 protein aggregates, which aberrantly localize to the nucleolus and hyperactivate the degradation of non-coding RNAs transcribed from the intergenic spacer of the rDNA repeats. This induces rDNA recombination and premature aging. Thus, our yeast models suggest trinucleotide repeat expansion of Ataxin-2 represents a gain-of-function mutation that may trigger neurodegeneration through alterations to the stability of repetitive DNA, uniting the “rDNA instability” and “protein aggregation” theories of aging. In addition, we discover a new mechanism that drives the mobility of retrotransposons via RNA-DNA hybrids. RNA-DNA hybrids are duplex nucleic acid structures that form when an RNA molecule binds to its DNA template. RNA-DNA hybrids can generate a tri-nucleic acid structure known as an R-loop that is composed of the RNA-DNA hybrid and a displaced single-stranded non-template DNA. We find that RNA-DNA hybrid structures and R-loops can form on extra-chromosomal Ty1 cDNA in yeast, but these structures drive Ty1 retromobility through distinct mechanisms. Ty1-associated R-loops drive retromobility through the canonical integration pathway, while Ty1-associated RNA-cDNA hybrids drive retromobility through a non-canonical homologous recombination-dependent pathway. Thus, the structure of an RNA-DNA hybrid (duplex versus triplex) may help dictate the mechanism through which it mobilizes transposable elements. Taken together, our yeast genetic studies reveal how intergenic non-coding RNAs and protein aggregates associated with repetitive DNA loci may collaboratively drive neurodegeneration and how RNA-DNA hybrids and R-loops differentially contribute to the mobilization of transposable elements.","abstract_has_math":false,"creators":["Ostrowski, Lauren Anne"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Laboratory Medicine and Pathobiology","school":null,"contributors":[],"advisors":["Mekhail, Karim"],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-06","date_published":"2020-06","updated_at":"2026-07-27T21:28:07Z","subjects":["Aging","Genome stability","Non-coding RNA","Repetitive DNA","Retrotransposons","Ribosomal DNA"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1807/121518","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Mekhail, Karim"]},{"key":"dc:contributor.department","label":"Department","values":["Laboratory Medicine and Pathobiology"]},{"key":"dc:creator","label":"Author","values":["Ostrowski, Lauren Anne"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-06"]},{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2022-06-22T04:09:23Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2022-06-22T04:09:23Z"]},{"key":"dc:date.issued","label":"Date","values":["2020-06"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Aging","Genome stability","Non-coding RNA","Repetitive DNA","Retrotransposons","Ribosomal DNA"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1807/121518"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The preservation of genome stability is essential to proper cellular function. Repetitive DNA sequences, such as the ribosomal DNA repeats (rDNA) and transposons, represent a large portion of eukaryotic genomes. Due to their repetitive nature, these loci are prone to aberrant recombination. In fact, rDNA repeat instability and increased transposon activity are hallmarks of neurodegenerative disease. Thus, cells employ multiple mechanisms to safeguard the integrity of repetitive loci. The RNA-binding protein Ataxin-2 (Pbp1 in yeast) regulates the stability of rDNA and yeast Ty1 retrotransposons. Interestingly, the human protein (ATXN2) undergoes trinucleotide repeat expansion in the neurodegenerative diseases spinocerebellar ataxia type II (SCA2) and amyotrophic lateral sclerosis. Here, we create yeast models of Ataxin-2-linked neurodegeneration. SCA2-modeling cells exhibit Ty1 protein aggregates, which aberrantly localize to the nucleolus and hyperactivate the degradation of non-coding RNAs transcribed from the intergenic spacer of the rDNA repeats. This induces rDNA recombination and premature aging. Thus, our yeast models suggest trinucleotide repeat expansion of Ataxin-2 represents a gain-of-function mutation that may trigger neurodegeneration through alterations to the stability of repetitive DNA, uniting the “rDNA instability” and “protein aggregation” theories of aging. In addition, we discover a new mechanism that drives the mobility of retrotransposons via RNA-DNA hybrids. RNA-DNA hybrids are duplex nucleic acid structures that form when an RNA molecule binds to its DNA template. RNA-DNA hybrids can generate a tri-nucleic acid structure known as an R-loop that is composed of the RNA-DNA hybrid and a displaced single-stranded non-template DNA. We find that RNA-DNA hybrid structures and R-loops can form on extra-chromosomal Ty1 cDNA in yeast, but these structures drive Ty1 retromobility through distinct mechanisms. Ty1-associated R-loops drive retromobility through the canonical integration pathway, while Ty1-associated RNA-cDNA hybrids drive retromobility through a non-canonical homologous recombination-dependent pathway. Thus, the structure of an RNA-DNA hybrid (duplex versus triplex) may help dictate the mechanism through which it mobilizes transposable elements. Taken together, our yeast genetic studies reveal how intergenic non-coding RNAs and protein aggregates associated with repetitive DNA loci may collaboratively drive neurodegeneration and how RNA-DNA hybrids and R-loops differentially contribute to the mobilization of transposable elements."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["RNA-binding Proteins and RNA-DNA Hybrids Regulate Repetitive DNA Stability in Health and Disease"]}]}],"canonical_facts":{"dc:contributor.advisor":["Mekhail, Karim"],"dc:contributor.department":["Laboratory Medicine and Pathobiology"],"dc:creator":["Ostrowski, Lauren Anne"],"dc:date":["2020-06"],"dc:date.accessioned":["2022-06-22T04:09:23Z"],"dc:date.available":["2022-06-22T04:09:23Z"],"dc:date.issued":["2020-06"],"dc:description.abstract":["The preservation of genome stability is essential to proper cellular function. Repetitive DNA sequences, such as the ribosomal DNA repeats (rDNA) and transposons, represent a large portion of eukaryotic genomes. Due to their repetitive nature, these loci are prone to aberrant recombination. In fact, rDNA repeat instability and increased transposon activity are hallmarks of neurodegenerative disease. Thus, cells employ multiple mechanisms to safeguard the integrity of repetitive loci. The RNA-binding protein Ataxin-2 (Pbp1 in yeast) regulates the stability of rDNA and yeast Ty1 retrotransposons. Interestingly, the human protein (ATXN2) undergoes trinucleotide repeat expansion in the neurodegenerative diseases spinocerebellar ataxia type II (SCA2) and amyotrophic lateral sclerosis. Here, we create yeast models of Ataxin-2-linked neurodegeneration. SCA2-modeling cells exhibit Ty1 protein aggregates, which aberrantly localize to the nucleolus and hyperactivate the degradation of non-coding RNAs transcribed from the intergenic spacer of the rDNA repeats. This induces rDNA recombination and premature aging. Thus, our yeast models suggest trinucleotide repeat expansion of Ataxin-2 represents a gain-of-function mutation that may trigger neurodegeneration through alterations to the stability of repetitive DNA, uniting the “rDNA instability” and “protein aggregation” theories of aging. In addition, we discover a new mechanism that drives the mobility of retrotransposons via RNA-DNA hybrids. RNA-DNA hybrids are duplex nucleic acid structures that form when an RNA molecule binds to its DNA template. RNA-DNA hybrids can generate a tri-nucleic acid structure known as an R-loop that is composed of the RNA-DNA hybrid and a displaced single-stranded non-template DNA. We find that RNA-DNA hybrid structures and R-loops can form on extra-chromosomal Ty1 cDNA in yeast, but these structures drive Ty1 retromobility through distinct mechanisms. Ty1-associated R-loops drive retromobility through the canonical integration pathway, while Ty1-associated RNA-cDNA hybrids drive retromobility through a non-canonical homologous recombination-dependent pathway. Thus, the structure of an RNA-DNA hybrid (duplex versus triplex) may help dictate the mechanism through which it mobilizes transposable elements. Taken together, our yeast genetic studies reveal how intergenic non-coding RNAs and protein aggregates associated with repetitive DNA loci may collaboratively drive neurodegeneration and how RNA-DNA hybrids and R-loops differentially contribute to the mobilization of transposable elements."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["http://hdl.handle.net/1807/121518"],"dc:subject":["Aging","Genome stability","Non-coding RNA","Repetitive DNA","Retrotransposons","Ribosomal DNA"],"dc:title":["RNA-binding Proteins and RNA-DNA Hybrids Regulate Repetitive DNA Stability in Health and Disease"],"dc:type":["Thesis"]},"updated_at":"2026-07-27T21:28:07Z"}