23QB

Adeno-associated virus serotype 2 VP1 basic regions in complex with importin alpha 2

Summary for 23QB

• Entry DOI: 10.2210/pdb23qb/pdb
• Descriptor: Capsid protein VP1, Importin subunit alpha-1, GLYCEROL, ... (4 entities in total)
• Functional Keywords: importin alpha, adeno associated complex, basic regions, transport, nucleus, nuclear localization, transport protein
• Biological source: Adeno-associated virus 2 Srivastava/1982; More
• Total number of polymer chains: 2
• Total formula weight: 61921.07

Authors

Hoad, M.,Forwood, J.K. (deposition date: 2026-02-13, release date: 2026-10-14, Last modification date: 2026-10-28)

Primary citation

Hoad, M.,Nematollahzadeh, S.,Cimichella, D.,Pavan, S.,Pierri, C.L.,Roby, J.A.,Alvisi, G.,Forwood, J.K.
Alternative bipartite arrangements of VP1 BR1-3 drive efficient nuclear import of AAV2 capsids.
J.Biol.Chem., 302:113562-113562, 2026

PubMed Abstract: Adeno-associated viruses (AAVs) are among the most extensively studied viral gene-therapy vectors, yet the mechanisms governing their nuclear entry remain incompletely understood. Efficient transduction requires that the AAV capsid, or its structural subunit VP1, traverse the nuclear envelope to deliver the therapeutic genome. The N-terminal region of VP1 contains three clustered basic regions (BR1-3) proposed to function as nuclear localization signals (NLSs). Here, we combine cellular, biophysical, structural, and computational modelling approaches to define the nuclear import mechanism of AAV2 VP1 at molecular resolution. We show that VP1 engages the classical importin-α/β1 (IMPα/β1) pathway and binds multiple IMPα paralogs with distinct affinities. Crystallographic and mutational analyses reveal that two intact BRs are required to simultaneously occupy the major and minor binding pockets of IMPα in a bipartite configuration. Structural data indicate that mouse IMPα2 (mIMPα2) preferentially accommodates BR1 and BR3 at these sites, however, functional studies demonstrate that mutation of individual BRs does not abolish IMP binding or nuclear accumulation. This robustness arises from the ability of BR2 to flexibly engage both binding pockets, enabling the formation of alternative bipartite arrangements (BR1-BR2, BR2-BR3, or BR1-BR3). Together, these findings reveal an unexpected versatility in how AAV2 VP1 exploits the IMPα binding sites, providing a structural basis for efficient capsid nuclear import. The flexibility of BR1-3 expands the current paradigm of viral NLS organization and suggests new strategies to fine-tune nuclear targeting AAV-based gene-therapy vectors.

PubMed: 42749258
DOI: 10.1016/j.jbc.2026.113562

Experimental method

X-RAY DIFFRACTION (2.25 Å)