ResearchPad - genome-integrity-and-transmission https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Rif1 Functions in a Tissue-Specific Manner To Control Replication Timing Through Its PP1-Binding Motif]]> https://www.researchpad.co/article/N166c12d0-122e-4359-b750-d48a9b1912c2 Replication initiation in eukaryotic cells occurs asynchronously throughout S phase, yielding early- and late-replicating regions of the genome, a process known as replication timing (RT). RT changes during development to ensure accurate genome duplication and maintain genome stability. To understand the relative contributions that cell lineage, cell cycle, and replication initiation regulators have on RT, we utilized the powerful developmental systems available in Drosophila melanogaster. We generated and compared RT profiles from mitotic cells of different tissues and from mitotic and endocycling cells of the same tissue. Our results demonstrate that cell lineage has the largest effect on RT, whereas switching from a mitotic to an endoreplicative cell cycle has little to no effect on RT. Additionally, we demonstrate that the RT differences we observed in all cases are largely independent of transcriptional differences. We also employed a genetic approach in these same cell types to understand the relative contribution the eukaryotic RT control factor, Rif1, has on RT control. Our results demonstrate that Rif1 can function in a tissue-specific manner to control RT. Importantly, the Protein Phosphatase 1 (PP1) binding motif of Rif1 is essential for Rif1 to regulate RT. Together, our data support a model in which the RT program is primarily driven by cell lineage and is further refined by Rif1/PP1 to ultimately generate tissue-specific RT programs.

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<![CDATA[Sex Chromosome Pairing Mediated by Euchromatic Homology in Drosophila Male Meiosis]]> https://www.researchpad.co/article/N29d0392a-de2c-4eab-b0ca-e9551ffed24c

Drosophila males have evolved a unique system of chromosome segregation in meiosis that lacks recombination. Chromosomes pair at selected sequences suggesting that early steps of meiosis may also differ in this organism...

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<![CDATA[Using Separation-of-Function Mutagenesis To Define the Full Spectrum of Activities Performed by the Est1 Telomerase Subunit in Vivo]]> https://www.researchpad.co/article/5c3544c5d5eed0c484d8f1b0

A leading objective in biology is to identify the complete set of activities performed by each gene. Identification of a comprehensive set of separation...

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<![CDATA[Origin, Composition, and Structure of the Supernumerary B Chromosome of Drosophila melanogaster]]> https://www.researchpad.co/article/5c22c6f6d5eed0c484aa2f03

In addition to a defined number of essential chromosomes, extra chromosomes called “B chromosomes” are present in roughly 15% of eukaryotic species. In this study, Hanlon et al. analyzed the recently discovered Drosophila melanogaster...

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<![CDATA[The Nucleotide Excision Repair Pathway Limits L1 Retrotransposition]]> https://www.researchpad.co/article/5b2afea9463d7e3de1fe866a

Long interspersed elements 1 (L1) are active mobile elements that constitute almost 17% of the human genome. They amplify through a “copy-and-paste” mechanism termed retrotransposition, and de novo insertions related to these elements have been reported to cause 0.2% of genetic diseases. Our previous data demonstrated that the endonuclease complex ERCC1-XPF, which cleaves a 3′ DNA flap structure, limits L1 retrotransposition. Although the ERCC1-XPF endonuclease participates in several different DNA repair pathways, such as single-strand annealing, or in telomere maintenance, its recruitment to DNA lesions is best characterized in the nucleotide excision repair (NER) pathway. To determine if the NER pathway prevents the insertion of retroelements in the genome, we monitored the retrotransposition efficiencies of engineered L1 elements in NER-deficient cells and in their complemented versions. Core proteins of the NER pathway, XPD and XPA, and the lesion binding protein, XPC, are involved in limiting L1 retrotransposition. In addition, sequence analysis of recovered de novo L1 inserts and their genomic locations in NER-deficient cells demonstrated the presence of abnormally large duplications at the site of insertion, suggesting that NER proteins may also play a role in the normal L1 insertion process. Here, we propose new functions for the NER pathway in the maintenance of genome integrity: limitation of insertional mutations caused by retrotransposons and the prevention of potentially mutagenic large genomic duplications at the site of retrotransposon insertion events.

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