Noémie Rochon, Centre de recherche du CHU de Québec - Université Laval

Noémie Rochon (Axe Maladies infectieuses et immunitaires, CRCHU de Québec, Université Laval; Faculté de médecine, département de Microbiologie-infectiologie et d'immunologie, Université Laval), Léa Lambert (Axe Maladies infectieuses et immunitaires, CRCHU de Québec, Université Laval; Faculté de médecine, département de Microbiologie-infectiologie et d'immunologie, Université Laval), Annie Gravel (Axe Maladies infectieuses et immunitaires, CRCHU de Québec, Université Laval), Amélie Fradet-Turcotte (Axe Oncologie, CRCHU de Québec, Université Laval; Faculté de médecine, département de Biologie moléculaire, de biologie médicale et de pathologie, Université Laval), Benedikt Kaufer (Institute of Virology, Freie University, Berlin, Germany), Louis Flamand (Axe Maladies infectieuses et immunitaires, CRCHU de Québec, Université Laval; Faculté de médecine, département de Microbiologie-infectiologie et d'immunologie, Université Laval)

Suppressing & Conquering

Human herpesvirus 6A (HHV-6A) can integrate its genome in the telomeres of the host cell. Viral telomeric repeats present at the viral genome extremities are required for integration into telomeres, suggesting that homologous recombination events are involved in this process. Our laboratory is interested in studying HHV-6A integration. We made the original discovery that immediate-early protein 1 (IE1) HHV-6A expression induces genomic instability by inhibiting the activity of the Ataxia telangiectasia mutated (ATM) kinase, a key regulator of double-strand DNA break repair. This inhibition is mediated by the C-terminal domain of IE1. To investigate the role of IE1 in viral infection and chromosomal integration, we generated a mutated virus deficient in ATM inhibition. En passant mutagenesis was performed on an HHV-6A recombinant BAC to generate a mutant lacking the C-terminal domain of IE1. Immunofluorescence assays detecting H2AX phosphorylation confirmed that IE1A inhibits ATM through its last eight residues. DNA and RNA were extracted during the first nine days following infection of permissive cells with wild-type and mutant recombinant viruses to quantify viral replication. Replication was higher for the wild-type virus than for the mutant, suggesting that inhibition of DNA double-strand break repair is important for the replication process. Infection of semi-permissive cells with wild-type and mutant recombinant viruses will allow quantification of the proportion of cells carrying integrated HHV-6A to determine whether inhibition of DNA double-strand break repair is important for the integration process. This project will provide further insight into IE1 function and its contribution to HHV-6A–induced genomic instability.