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Abstract At the heart of all biological processes lies the control of nuclear gene expression, which is primarily achieved through the action of transcription factors (TFs) that generally contain a nuclear localization signal (NLS) to facilitate their transport into the nucleus. However, some TFs reside in the cytoplasm in a transcriptionally inactive state and only enter the nucleus in response to specific signals, which in plants include biotic or abiotic stresses. These extra-nuclear TFs can be found in the cytosol or associated with various membrane systems, including the endoplasmic reticulum and plasma membrane. They may be integral proteins with transmembrane domains or associate peripherally with the lipid bilayer via acylation or membrane-binding domains. Although over 30 plant TFs, most of them involved in stress responses, have been experimentally shown to reside outside the nucleus, computational predictions suggest that this number is much larger. Understanding how extra-nuclear TFs are trafficked into the nucleus is essential for reconstructing transcriptional regulatory networks that govern major cellular pathways in response to biotic and abiotic signals. Here, we provide a perspective on what is known on plant extranuclear-nuclear TF retention, nuclear trafficking, and the post-translational modifications that ultimately enable them to regulate gene expression upon entering the nucleus.
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Coordination of NMCP1- and NMCP2-class proteins within the plant nucleoskeleton
Plants lack lamin proteins but contain a class of coiled-coil proteins that serve as analogues to form a laminal structure at the nuclear periphery. These nuclear matrix constituent proteins (NMCPs) play important roles in regulating nuclear morphology and are partitioned into two distinct groups. We investigated Arabidopsis NMCPs (called CRWNs) to study the interrelationship between the three NMCP1-type paralogues (CRWN1, 2, and 3) and the lone NMCP2-type paralogue, CRWN4. An examination of crwn mutants using protein immunoblots demonstrated that CRWN4 abundance depends on the presence of the NMCP1-type proteins, particularly CRWN1. The possibility that CRWN4 is coimported into the nucleus with nuclear localization signal (NLS)-bearing paralogues in the NMCP1-clade was discounted based on recovery of a crwn4-2 missense allele that disrupts a predicted NLS and lowers the abundance of CRWN4 in the nucleus. Further, a screen for mutations that suppress the effects of the crwn4-2 mutation led to the discovery of a missense allele, impa-1 G146E , in one of the nine importin-α genes in the Arabidopsis genome. Our results indicate that the CRWN4 carries a functional NLS that interacts with canonic nuclear import machinery. Once imported, the level of CRWN4 within the nucleus is modulated by the abundance of NMCP1 proteins.
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- Award ID(s):
- 2022048
- PAR ID:
- 10253080
- Editor(s):
- Misteli, Tom
- Date Published:
- Journal Name:
- Molecular Biology of the Cell
- Volume:
- 31
- Issue:
- 26
- ISSN:
- 1059-1524
- Page Range / eLocation ID:
- 2948 to 2958
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1091/mbc.E19-08-0464
