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The net repressor is regulated by nuclear export in response to anisomycin, UV, and heat shock
C Ducret1, S M Maira, A Dierich
1Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, 67404 Illkirch Cedex, France.
Abstract:
The ternary complex factors (TCFs) are targets for Ras/mitogen-activated protein kinase signalling pathways. They integrate the transcriptional response at the level of serum response elements in early-response genes, such as the c-fos proto-oncogene. An important aim is to understand the individual roles played by the three TCFs, Net, Elk1, and Sap1a. Net, in contrast to Elk1 and Sap1a, is a strong repressor of transcription. We now show that Net is regulated by nuclear-cytoplasmic shuttling in response to specific signalling pathways. Net is mainly nuclear under both normal and basal serum conditions. Net contains two nuclear localization signals (NLSs); one is located in the Ets domain, and the other corresponds to the D box. Net also has a nuclear export signal (NES) in the conserved Ets DNA binding domain. Net is apparently unique among Ets proteins in that a particular leucine in helix 1, a structural element, generates a NES. Anisomycin, UV, and heat shock induce active nuclear exclusion of Net through a pathway that involves c-Jun N-terminal kinase kinase and is inhibited by leptomycin B. Nuclear exclusion relieves transcriptional repression by Net. The specific induction of nuclear exclusion of Net by particular signalling pathways shows that nuclear-cytoplasmic transport of transcription factors can add to the specificity of the response to signalling cascades.
Insights
Net, a transcription repressor, is regulated by nuclear export in response to specific signals. This shuttling mechanism enhances the specificity of cellular responses to signaling pathways.
Area of Science:
- Molecular Biology
- Cell Signaling
Background:
- Ternary complex factors (TCFs) integrate transcriptional responses to signaling pathways like Ras/MAPK.
- Understanding the distinct roles of TCFs (Net, Elk1, Sap1a) is crucial.
- Net functions as a potent transcriptional repressor, unlike Elk1 and Sap1a.
Purpose of the Study:
- To investigate the regulation of Net by nuclear-cytoplasmic shuttling.
- To elucidate the signaling pathways that control Net's localization and function.
- To determine how Net's transport impacts transcriptional repression.
Main Methods:
- Analysis of Net's nuclear localization signals (NLSs) and nuclear export signal (NES).
- Investigating Net's localization changes in response to anisomycin, UV, and heat shock.
- Identifying the signaling pathway components involved in Net's nuclear exclusion, including JNK kinase and leptomycin B inhibition.
Main Results:
- Net possesses distinct NLSs and a unique NES within its Ets DNA binding domain.
- Specific stimuli (anisomycin, UV, heat shock) induce Net's active nuclear exclusion.
- This exclusion is mediated by a pathway involving JNK kinase and is sensitive to leptomycin B.
- Nuclear exclusion of Net alleviates its transcriptional repression.
Conclusions:
- Net's localization is dynamically regulated by signaling pathways through nuclear-cytoplasmic shuttling.
- This shuttling mechanism contributes to the specificity of cellular responses to signaling cascades.
- Net's unique regulation highlights the importance of transport in controlling transcription factor activity.