期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：42
页码：E5725-E5733
DOI：10.1073/pnas.1513876112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe nucleus is structured into chromatin and interchromatin compartments. Its sieve-like architecture permits individual proteins to rapidly diffuse while large macromolecular assemblies are corralled in the interchromatin. Herpesvirus capsids assemble in the nucleus and have to access the nuclear periphery for exit. It was hypothesized that nuclear herpesvirus capsids recruit filamentous actin and molecular motor protein to overcome nuclear entrapment. Here we use "ring-sheet" microscopy to track nuclear capsids with high spatiotemporal resolution. We report that nuclear herpesvirus capsids do not use directed motility. Instead, virus infection changes nuclear architecture, which allows capsids to reach the nuclear membranes by diffusion. Our findings illustrate a pathway for very large macromolecular assemblies to cross the nucleoplasm without directed motility. The nuclear chromatin structure confines the movement of large macromolecular complexes to interchromatin corrals. Herpesvirus capsids of approximately 125 nm assemble in the nucleoplasm and must reach the nuclear membranes for egress. Previous studies concluded that nuclear herpesvirus capsid motility is active, directed, and based on nuclear filamentous actin, suggesting that large nuclear complexes need metabolic energy to escape nuclear entrapment. However, this hypothesis has recently been challenged. Commonly used microscopy techniques do not allow the imaging of rapid nuclear particle motility with sufficient spatiotemporal resolution. Here, we use a rotating, oblique light sheet, which we dubbed a ring-sheet, to image and track viral capsids with high temporal and spatial resolution. We do not find any evidence for directed transport. Instead, infection with different herpesviruses induced an enlargement of interchromatin domains and allowed particles to diffuse unrestricted over longer distances, thereby facilitating nuclear egress for a larger fraction of capsids.
