Structural characterization of human cytomegalovirus (HCMV) terminase by Cryo-EM

• Grant number: 22/00384-2
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Start date: May 30, 2022
• End date: May 29, 2023
• Field of knowledge: Biological Sciences - Biophysics - Molecular Biophysics
• Principal Investigator: Glaucius Oliva
• Grantee: Gabriela Dias Noske
• Supervisor: Kay Grunewald
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Institution abroad: Leibniz Institute for Experimental Virology (HPI), Germany
• Associated to the scholarship: 18/25600-4 - Discovery and development of antiviral candidates against Yellow Fever virus based on the structure of the NS2B-NS3 protease complex, BP.DD

Abstract

Human cytomegalovirus (HCMV) is a beta-herpesvirus belonging to the Herpesviridae family and Cytomegalovirus genus. The virus is widely spread among the world population establishing a latent infection, and it represents one of the most frequent causes of death among immunocompromised patients and one of the main causes of congenital birth problems. The viral genome is composed by a linear double-stranded DNA of ~230 kb that is responsible for codifying at least 250 open reading frames (ORFs). Several viral proteins are involved in the process of DNA packing into the viral capsid and DNA cleavage, which includes the terminase complex. The terminases are enzymatic hetero-oligomeric complexes, composed of the subunits pUL56, pUL89 and pUL51 in HCMV. The complex is thought to mediate the recognition of the cis-acting packaging signals pac1 and pac2 motifs. In despite of the terminases being extensively studied in the past decades, details of the molecular and structural mechanism of DNA cleavage/packing remains still incompletely elucidated. The HCMV terminase constitutes a highly specific viral protein, with no homologous in mammals and represents an attractive target for drug development. Letermovir is a recently approved antiviral drug targeting the HCMV terminase complex, however, its mode of action is so far not fully understood.Single particle analysis by cryo-EM allows to obtain structures of large protein complexes and constitutes a promising technique for structural studies of terminases. Thus, the main goal of this BEPE project will be to structurally characterize the terminase complex of HCMV using cryo-EM, including DNA bound forms, letermovir resistant mutants and complexes with other proteins involved in DNA packing and cleavage. After the internship abroad period, the gained experience in cryo-EM will be applied in the ongoing PhD project and to contribute to the establishment of cryo-EM at the IFSC structural biology and drug discovery group in São Carlos/Brazil. (AU)