DNA replication is an essential process for genome duplication, cell division and ultimately organismal survival that ensures faithful transmission of the genome to progeny. Certain genomic loci represent major obstacles to DNA replication including fragile sites, G-rich tracts and repetitive sequences, such as ribosomal DNA and telomeres. Mammalian telomeres have the propensity to adopt complex DNA secondary structures, including telomere-loops and telomeric G-quadruplex DNA, which are believed to play essential roles in telomere maintenance. However, recent work has established that these structures are also a hindrance to DNA replication and failure to stabilise, repair or restart the replication fork is a potential source of genome instability, the hallmark of many diseases including cancer.
Increasing evidence suggests that telomere secondary structures that are essential for chromosome end protection and appropriate chromosome segregation might also represent a hindrance during DNA replication. Thus cells have developed mechanisms to ensure proper genome duplication that require specific factors to alleviate DNA replication stress, which is causative of genome instability and ultimately tumourigenesis. I am confident that the proposed aims will contribute to an improved understanding of the structure and nature of telomere replication stress in eukaryotes. Ultimately, the program of research will provide a framework for comprehending the contributions of replication stress response factors in general DNA replication and cancer in humans. My following proposal describes three complementary projects that will focus on telomere replication which specifically aim to address the key questions: (1) what are the enzymatic activities that result in fragile telomeres; (2) what is the structure of telomere fragility; (3) what is the the role of Activity-Dependent Neuroprotective Protein (ADNP) in telomere biology and the importance of telomere instability in some neurological disorders including a syndromic form of autism-like disorder.
My research financed with this ERC starting grant has enabled my group to identify a pathway of repair when telomeres are under replication stress (Porreca et al., 2020; eLife), a novel RNA helicase SKIV2L part of hSKI complex involved in MRNA mediated RNA decay pathway that is also responsible for regulating RNA-DNA hybrids at telomeres and suppressing telomere replication stress and DNA damage (Herrera-Moyano et al., 2021, in revision in Cell reports), contribute to the understanding of in-cellulo G-quadruplex dynamics in live cell imaging (Summers et al., 2020, Nature Communications) and help develop new probes (Lewis et al., 2021, Chemistry), contribute to the understanding of senescence pathways when cells are subjected to telomere DNA damage stress (Innes et al., 2021, Genes & Development).
