Nucleocytoplasmic shuttling by nucleoporins Nup153 and Nup214 and CRM1-dependent nuclear export control the subcellular distribution of latent Stat1.
Interferon stimulation of cells leads to the tyrosine phosphorylation of latent Stat1 and subsequent transient accumulation in the nucleus that requires canonical transport factors. However, the mechanisms that control the predominantly cytoplasmic localization in unstimulated cells have not been resolved. We uncovered that constitutive energy- and transport factor-independent nucleocytoplasmic shuttling is a property of unphosphorylated Stat1, Stat3, and Stat5. The NH(2)- and COOH-terminal Stat domains are generally dispensable, whereas alkylation of a single cysteine residue blocked cytokine-independent nuclear translocation and thus implicated the linker domain into the cycling of Stat1. It is revealed that constitutive nucleocytoplasmic shuttling of Stat1 is mediated by direct interactions with the FG repeat regions of nucleoporin 153 and nucleoporin 214 of the nuclear pore. Concurrent active nuclear export by CRM1 created a nucleocytoplasmic Stat1 concentration gradient that is significantly reduced by the blocking of energy-requiring translocation mechanisms or the specific inactivation of CRM1. Thus, we propose that two independent translocation pathways cooperate to determine the steady-state distribution of Stat1.
Marg
Andreas
A
Abteilung Zellulare Signalverarbeitung, Leibniz-Forschungsinstitut fur Molekulare Pharmakologie, Robert-Rossle-Str. 10, 13125 Berlin, Germany.
Shan
Ying
Y
Meyer
Thomas
T
Meissner
Torsten
T
Brandenburg
Martin
M
Vinkemeier
Uwe
U
D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000502:physiology*; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D016296:Mutagenesis; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D010957:Plasmids; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins / Q000378:metabolism; D050794:STAT1 Transcription Factor; D013347:Subcellular Fractions / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D016335:Zinc Fingers; D000097606:Exportin 1 Protein
D004268:DNA-Binding Proteins; D028884:Karyopherins; D028861:Nuclear Pore Complex Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; D015534:Trans-Activators; D000097606:Exportin 1 Protein; C079377:NUP153 protein, human; C085914:NUP214 protein, human; C513084:Nup153 protein, mouse; C490093:Nup214 protein, mouse; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse