Targeting proteins to the plant nuclear envelope

Area of Science:

• Cell Biology
• Molecular Biology
• Plant Science

Background:

• The nuclear envelope and nuclear pore complex regulate transport between the cytoplasm and nucleoplasm.
• Mechanisms for targeting proteins, especially transmembrane-domain proteins, to the plant nuclear envelope and pore are not well understood.
• Plant-specific adaptations in these targeting processes remain largely unexplored.

Purpose of the Study:

• To investigate the sorting mechanisms for transmembrane-domain proteins to the plant nuclear envelope and nuclear pore.
• To identify protein-protein interactions involved in nuclear pore protein association.
• To determine plant-specific aspects of nuclear envelope and pore targeting.

Main Methods:

• Investigated the targeting of plant RanGAP (Ran GTPase-activating protein), a nuclear pore-associated protein.
• Utilized WIP (WPP-domain-interacting protein) and WIT (WPP-domain-interacting tail-anchored protein) families involved in RanGAP targeting.
• Examined the roles of protein domains (transmembrane, coiled-coil) and chaperone proteins (HSC70) in targeting.

Main Results:

• Plant RanGAP is targeted to the nuclear pore via a plant-specific mechanism involving WIP and WIT proteins.
• WIP or WIT proteins are sufficient for RanGAP targeting in differentiated root cells, but both are required in meristematic cells.
• WIP targeting depends on a C-terminal transmembrane domain, while WIT targeting requires a coiled-coil domain and is aided by HSC70 and WPP proteins.

Conclusions:

• Identified a novel, plant-specific mechanism for targeting proteins to the nuclear pore, involving WIP and WIT protein families.
• Demonstrated differential requirements for WIP and WIT proteins in targeting based on cell differentiation state.
• Elucidated the roles of specific protein domains and chaperones in nuclear envelope and nuclear pore targeting in land plants.