Characterizing the Role of Lamin B1 Acetylation in Regulating the Integrity of the Nuclear Periphery

Abstract

The beta-herpesvirus human cytomegalovirus (HCMV) is a ubiquitous pathogen that causes critical diseases in pregnant women and immunocompromised patients, yet effective vaccines and antiviral treatments remain elusive. HCMV relies on the spatiotemporal remodeling of host cell organization and the rewiring of organelle and protein functions for virus replication and spread. A key subcellular location for these processes is the nucleus, where viral genome replication, gene expression, DNA packaging, and capsid assembly all occur. Evidence points to the acetylation of host immune proteins as an important post-translational modification in regulating their subcellular localization and/or protein-protein interactions and functions during viral infection. Additionally, our lab recently showed that acetylation of nuclear laminar proteins inhibits viral replication through the maintenance of nuclear integrity. This was primarily mediated by a site-specific acetylation of lamin B1 (LMNB1), a core component of laminar structure, at lysine 134 (K134). In my thesis, I utilize molecular virology, mass spectrometry-based proteomics, and confocal microscopy to further characterize the function of LMNB1 acetylation during HCMV infection. I find that acetylation at K134 increases LMNB1 association with nuclear periphery proteins, impairs viral genome replication, and inhibits the production of viral proteins needed for DNA packaging. I also expand our understanding of acetylated LMNB1 functions by demonstrating that site-specific acetylations can toggle LMBN1 between an anti-viral (residues K261, K389) and pro-viral (K102) state. Finally, I show that the role of LMNB1 acetylation in stabilizing nuclear integrity broadly impacts cell biology by characterizing a novel function in regulating the G1/S checkpoint of the cell cycle. Taken together, this thesis further 10 demonstrates novel, critical roles for LMNB1 acetylation in the tug-of-war between viruses and their hosts and uncovers LMNB1 acetylation as a regulatory mechanism in cell cycle progression.