Inositol Polyphosphates: Mechanisms of Action and Integration with DNA Damage Response

• Grant number: 24/10865-3
• Support Opportunities: Regular Research Grants
• Start date: November 01, 2024
• End date: October 31, 2026
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: José Renato Rosa Cussiol
• Grantee: José Renato Rosa Cussiol
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Associated researchers: Luis Eduardo Soares Netto
• Associated scholarship(s): 25/00749-9 - Characterization of a potential post-translational regulatory mechanism of Kcs1 protein function during the DNA damage response in Saccharomyces cerevisiae., BP.IC

Abstract

Inositol polyphosphates and pyrophosphates (IPs and PP-IPs) constitute a ubiquitous class of highly charged and water-soluble molecules conserved from yeast to humans, playing fundamental roles in cellular homeostasis and implicated in human diseases such as diabetes and cancer. Despite their greater diversity compared to lipid phosphoinositides, IPs remain less characterized to date. In recent years, attention has been focused on elucidating the relationship of IPs with nuclear processes such as gene expression regulation, telomere maintenance, mRNA export, DNA replication, and repair. Our investigation is focused on the function of these molecules in the DNA damage response (DDR) using Saccharomyces cerevisiae as a model organism. Our preliminary results reveal that the deletion of inositol polyphosphate kinases (IPKs) Ipk2 and Kcs1 confers hypersensitivity to different genotoxins. Particularly, the deletion of Kcs1 leads to hyperactivation of the checkpoint kinase Rad53, increased levels of gamma-H2A, and decreased nuclear foci of Rad52 in the presence of the radiomimetic zeocin, indicating that the PP-IPs synthesized by Kcs1 act in DNA repair by homologous recombination. Furthermore, genetic interaction analyses between IPKs show that the deletion of Kcs1 and Ipk2 leads to a synthetic lethality phenotype in the presence of hydroxyurea (HU) and failure to activate Rad53, suggesting a role of IPs in the response to replication stress. Collectively, these results suggest that IPs and PP-IPs modulate DDR through unknown mechanisms. Therefore, employing a multidisciplinary approach that integrates large-scale analyses such as proteomics/phosphoproteomics and synthetic genetic array (SGA) with genetic and biochemical assays, this project aims to elucidate the molecular mechanisms by which IP metabolism integrates with DDR. Since IPs are molecules present in all eukaryotes, this research program aims to contribute to a better understanding of the mechanisms of DNA damage response and, consequently, in preventing the accumulation of genomic instability, the driving force behind tumorigenic processes. (AU)