NDLI: Importins fulfil a dual function as nuclear import receptors and cytoplasmic chaperones for exposed basic domains

Content Provider	PubMed Central
Author	Stefan, Jäkel Mingot, José-manuel Petra, Schwarzmaier Hartmann, Enno Dirk, Görlich
Copyright Year	2002
Abstract	Many nuclear transport pathways are mediated by importin β-related transport receptors. Here, we identify human importin (Imp) 4b as well as mouse Imp4a, Imp9a and Imp9b as novel family members. Imp4a mediates import of the ribosomal protein (rp) S3a, while Imp9a and Imp9b import rpS7, rpL18a and apparently numerous other substrates. Ribosomal proteins, histones and many other nuclear import substrates are very basic proteins that aggregate easily with cytoplasmic polyanions such as RNA. Imp9 effectively prevents such precipitation of, for example, rpS7 and rpL18a by covering their basic domains. The same applies to Imp4, Imp5, Imp7 and Impβ and their respective basic import substrates. The Impβ–Imp7 heterodimer appears specialized for the most basic proteins, such as rpL4, rpL6 and histone H1, and is necessary and sufficient to keep them soluble in a cytoplasmic environment prior to rRNA or DNA binding, respectively. Thus, just as heat shock proteins function as chaperones for exposed hydrophobic patches, importins act as chaperones for exposed basic domains, and we suggest that this represents a major and general cellular function of importins.
Related Links	http://dx.doi.org/10.1093/emboj/21.3.377
Ending Page	386
Page Count	10
Starting Page	377
File Format	PDF
ISSN	02614189
e-ISSN	14602075
Journal	The EMBO Journal
Issue Number	3
Volume Number	21
Language	English
Publisher	Oxford University Press
Publisher Date	2002-02-01
Access Restriction	Open
Rights Holder	Oxford University Press
Subject Keyword	Biochemistry, Genetics and Molecular Biology(all) Immunology and Microbiology(all) Neuroscience(all) Molecular Biology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Neuroscience Immunology and Microbiology Medicine Molecular Biology

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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