Correlation of CRM1-NES affinity with nuclear export activity.

Area of Science:

• Cell Biology
• Molecular Biology
• Structural Biology

Background:

• CRM1 (Exportin1/XPO1) is a key nuclear export receptor.
• It recognizes nuclear export signals (NESs) on diverse protein cargoes.
• NESs are characterized by hydrophobic residues and variable structures.

Purpose of the Study:

• To investigate the relationship between CRM1-NES binding affinity and nuclear export activity.
• To understand the structural basis for exceptionally tight CRM1-NES interactions.
• To design novel CRM1 inhibitors based on mechanistic insights.

Main Methods:

• Assessed nuclear export activity of 24 NES peptides in cellular assays.
• Measured CRM1-NES binding affinities using dissociation constants (K_ds).
• Determined the crystal structure of CRM1 bound to MVM NS2 NES.

Main Results:

• A linear correlation was observed between binding affinity and export activity for K_ds in the nanomolar to micromolar range.
• NESs with K_ds outside this range exhibited reduced export activity.
• Unusually tight binding of MVM NS2 NES was attributed to intramolecular contacts stabilizing its conformation.
• This led to the design of novel CRM1 inhibitors with picomolar affinity.

Conclusions:

• CRM1 binding affinity is a critical determinant of nuclear export efficiency for most NESs.
• Intramolecular interactions within NESs can lead to exceptionally high CRM1 affinity.
• The study provides a mechanistic basis for developing highly potent CRM1-targeting therapeutics.