Meet the jury: Herpesvirus infection-induced remodification of chromatin organization facilitates nuclear egress of viral capsids, Prof Maija Vihinen-Ranta

You are kindly invited to the meet the jury lecture of prof. Maija Vihinen-Ranta, University of Jyväskylä on ‘Herpesvirus infection-induced remodification of chromatin organization facilitates nuclear egress of viral capsids’

Date: September 30, 2026, from 11 AM to 12.30PM

Venue: Rega – Rega Instituut – Aula Erik De Clercq – 06.B204

Link: https://livestream.kuleuven.be, PIN: 926555

Registration for the seminar: Meet-the-jury lecture prof. Maija Vihinen-Ranta
About the lecture

Viral infections can cause drastic changes in nuclear function and structure. Herpes simplex virus type 1 (HSV-1) infection leads to the formation and expansion of spherical, nuclear membraneless viral replication compartments for viral DNA replication and progeny capsid assembly. This is accompanied by reorganization of the host chromatin toward the nuclear periphery. Virus capsids are assembled and packaged in the nucleus and move by diffusion through the nucleoplasm to the nuclear envelope for egress. The peripheral chromatin presents a restrictive barrier to capsid motion. Our live-cell imaging and single-particle tracking studies show that later in infection, this barrier becomes more permissive, and the probability of capsids entering the chromatin increases. This is supported by our cryo-soft X-ray tomography (SXT) analysis, which shows an increased presence of infection-induced low-density gaps in peripheral chromatin. Analyses of capsid motion revealed that it was subdiffusive and that the diffusion coefficients were lower in the chromatin than in regions lacking chromatin. In addition, the diffusion coefficient in both regions increased during infection. Virus-induced changes in nuclear organization lead to changes in nuclear biomechanics in host cells. Our atomic force microscopy (AFM), fluorescence microscopy, volume electron microscopy (EM), and SXT, as well as computational modeling studies, show that nuclei become softer as infection progresses, as the nuclear structure undergoes profound changes and the nuclear lamina is modified. Our experimental findings and modeling reveal that, during infection, the nucleus is subject to changes in multiple mechanical forces that collectively lead to nuclear deformation and decreased nuclear stiffness. The monitored decrease in forces, such as LINC-complex-mediated cytoskeletal pulling and Ca2+ ion concentration, is known to lead to lower levels of chromatin condensation. These changes most likely trigger the local remodeling and decondensation of chromatin and possibly affect chromatin dynamics, which could explain facilitated capsid diffusion through the chromatin during the nuclear egress of viral capsids.

About the speaker

Maija Vihinen-Ranta is a Finnish cell biologist and virologist at the University of Jyväskylä, where she is currently a Research Director in the Department of Biological and Environmental Science.
The research of Research Director Maija Vihinen-Ranta’s group focuses on the interaction between viruses, herpes simplex virus 1 (HSV-1), and parvoviruses, and the nucleus. HSV-1 infection leads to the formation and expansion of the membraneless viral replication compartment for viral DNA replication and progeny capsid assembly. This is accompanied by the reorganization of host chromatin toward the nuclear periphery. We wish to understand the mechanisms of HSV-1-induced changes in nuclear structures, including chromatin and nucleoli, and the dynamics of viral capsids in the nucleus. For example, we have shown that capsid transport through chromatin is the rate-limiting step for nuclear capsid exit and that the restrictive chromatin barrier becomes more permissive at late infection, allowing herpesvirus capsid diffusion toward the nuclear envelope. We are also interested in infection-induced changes in nuclear biomechanics and the structure and function of mitochondria. Our parvovirus studies elucidate infection-induced nucleolar changes, intranuclear mobility, and nuclear export of parvovirus capsids. Grants from the EU Horizon project, the Academy of Finland, and the Jane and Aatos Erkko Foundation have funded the lab.