sirolimus and Fanconi-Anemia

We have previously demonstrated that Fanconi anemia (FA) proteins work in concert with other FA and non-FA proteins to mediate stalled replication fork restart. Previous studies suggest a connection between the FA protein FANCD2 and the non-FA protein mechanistic target of rapamycin (mTOR). A recent study showed that mTOR is involved in actin-dependent DNA replication fork restart, suggesting possible roles in the FA DNA repair pathway. In this study, we demonstrate that during replication stress mTOR interacts and cooperates with FANCD2 to provide cellular stability, mediate stalled replication fork restart, and prevent nucleolytic degradation of the nascent DNA strands. Taken together, this study unravels a novel functional cross-talk between two important mechanisms: mTOR and FA DNA repair pathways that ensure genomic stability.

Topics: Aphidicolin; Cell Survival; DNA; DNA Repair; DNA Replication; Fanconi Anemia; Fanconi Anemia Complementation Group D2 Protein; Fibroblasts; Genome, Human; Genomic Instability; Humans; Hydroxyurea; Mitomycin; Primary Cell Culture; Protein Binding; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Fanconi Anemia (FA) is an inherited bone marrow failure syndrome caused by mutation in FA pathway proteins, involved in Interstrand Cross Link (ICL) repair. FA cells exhibit in vitro proliferation arrest due to accumulated DNA damage, hence understanding the rescue mechanism that renders proliferation advantage is required. Gene expression profiling performed in FA patients Peripheral Blood Mononuclear Cells (PBMCs) revealed a wide array of dysregulated biological processes. Functional enrichment and gene clustering analysis showed crippled autophagy process and escalated Notch signalling pathway in FA clinical samples and cell lines. Notch pathway mediators overexpression were reverted in FANCA mutant cells when treated with Rapamycin, an autophagy inducer. Additionally, Rapamycin stabilized cell viability after treatment with the DNA damaging agent, MitomycinC (MMC) and enhanced cell proliferation genes expression in FANCA mutant cells. Inherently FANCA mutant cells express impaired autophagy; thus activation of autophagy channelizes Notch signalling cascade and sustains cell viability.

Topics: Autophagy; Autophagy-Related Proteins; Cell Line; Cell Proliferation; Cell Survival; Fanconi Anemia; Fanconi Anemia Complementation Group A Protein; Gene Expression Profiling; Humans; Mutation; Receptor, Notch1; S Phase; Signal Transduction; Sirolimus