Adeno-associated virus type 2 (AAV2) uncoating is a stepwise process and is linked to structural reorganization of the nucleolus

PLoS Pathog. 2022 Jul 11;18(7):e1010187. doi: 10.1371/journal.ppat.1010187. eCollection 2022 Jul.


Nucleoli are membrane-less structures located within the nucleus and are known to be involved in many cellular functions, including stress response and cell cycle regulation. Besides, many viruses can employ the nucleolus or nucleolar proteins to promote different steps of their life cycle such as replication, transcription and assembly. While adeno-associated virus type 2 (AAV2) capsids have previously been reported to enter the host cell nucleus and accumulate in the nucleolus, both the role of the nucleolus in AAV2 infection, and the viral uncoating mechanism remain elusive. In all prior studies on AAV uncoating, viral capsids and viral genomes were not directly correlated on the single cell level, at least not in absence of a helper virus. To elucidate the properties of the nucleolus during AAV2 infection and to assess viral uncoating on a single cell level, we combined immunofluorescence analysis for detection of intact AAV2 capsids and capsid proteins with fluorescence in situ hybridization for detection of AAV2 genomes. The results of our experiments provide evidence that uncoating of AAV2 particles occurs in a stepwise process that is completed in the nucleolus and supported by alteration of the nucleolar structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Capsid Proteins / metabolism
  • Dependovirus* / genetics
  • HeLa Cells
  • Humans
  • In Situ Hybridization, Fluorescence
  • Virus Uncoating*


  • Capsid Proteins

Supplementary concepts

  • Adeno-associated virus-2

Grants and funding

C.F. was supported by Swiss National Science Foundation No. 310030_184766 ( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.