Gavin Zhao

Program: Molecular Microbiology and Microbial Pathogenesis

Current advisor: Gaya K. Amarasinghe, PhD

Undergraduate university: Boston College, 2019

Enrollment year: 2021

Research summary
Characterization of multifunctional Ebolavirus VP24 to define the role of conserved residues in virus replication and adaptation

Ebolavirus viral protein 24 (VP24) is a multifunctional protein with two currently known functions. First, VP24 binds to NPI-1 subfamily of importins and prevents nuclear translocation of phosphorylated signal transducer and activator of transcription 1 (STAT1), thereby antagonizing interferon signaling. Second, VP24 interacts with multiple components of viral ribonucleoprotein complex such as nucleoprotein to facilitate viral genome packaging4. VP24 is also implicated in viral transcription and productive egress of nascent virions. Laboratory adaptation of Ebola virus (EBOV) isolated from human patients into rodent animal models have led to discovery of adaptive mutations in VP24. However, how these multiple functions are carried out by this virally encoded 24 kDa protein is not fully understood. Specifically, how VP24 facilitates multiple aspects of viral replication and potentially impact zoonosis remains a key gap.
Recent data reveal that EBOV VP24 is trafficked between cytoplasmic and nuclear compartments, and proteomic data have identified host nuclear proteins as interactors of EBOV VP24. More importantly, VP24 mutations that disrupt its interaction with karyopherin α5 (KPNA5) lead to interferon-dependent and interferon- independent defects in viral titers without affecting their NP-related functions. Our preliminary data suggest that host proteins bearing the classical nuclear localization signals can co-transport with VP24. These data strongly suggest that VP24 has yet uncharacterized functions, including potential roles in the nucleus. Underscoring the importance of VP24 in the viral replication cycle and potential role in cross-species transmission, in vivo serial passaging experiments revealed that VP24 residue changes are required or sufficient for adaptation of EBOV into rodent animal models. Some of these changes are distal to known interfaces. Further, primary sequence alignment of clinical and laboratory isolates of viruses in the Ebolavirus genus reveals patches of amino acids that are conserved among isolates, but do not locate near NP or KPNA interaction interfaces. How these multiple functions are facilitated by VP24 is a major gap in the field. I will determine the functional significance of conserved residues in VP24 in viral replication, and their relationship with known binding sites. Through these studies, I also expect to identify how VP24 contributes to adaptation to new host species.

Graduate publications