Author:
van Roeyen Claudia RC,Scurt Florian G,Brandt Sabine,Kuhl Vanessa A,Martinkus Sandra,Djudjaj Sonja,Raffetseder Ute,Royer Hans-Dieter,Stefanidis Ioannis,Dunn Sandra E,Dooley Steven,Weng Honglei,Fischer Thomas,Lindquist Jonathan A,Mertens Peter R
Abstract
Abstract
Background
The Y-box protein-1 (YB-1) fulfills pleiotropic functions relating to gene transcription, mRNA processing, and translation. It remains elusive how YB-1 shuttling into the nuclear and cytoplasmic compartments is regulated and whether limited proteolysis by the 20S proteasome releases fragments with distinct function(s) and subcellular distribution(s).
Results
To address these questions, mapping of domains responsible for subcellular targeting was performed. Three nuclear localization signals (NLS) were identified. NLS-1 (aa 149-156) and NLS-2 (aa 185-194) correspond to residues with unknown function(s), whereas NLS-3 (aa 276-292) matches with a designated multimerization domain. Nuclear export signal(s) were not identified. Endoproteolytic processing by the 20S proteasome before glycine 220 releases a carboxy-terminal fragment (CTF), which localized to the nucleus, indicating that NLS-3 is operative. Genotoxic stress induced proteolytic cleavage and nuclear translocation of the CTF. Co-expression of the CTF and full-length YB-1 resulted in an abrogated transcriptional activation of the MMP-2 promoter, indicating an autoregulatory inhibitory loop, whereas it fulfilled similar trans-repressive effects on the collagen type I promoter.
Conclusion
Compartmentalization of YB-1 protein derivatives is controlled by distinct NLS, one of which targets a proteolytic cleavage product to the nucleus. We propose a model for an autoregulatory negative feedback loop that halts unlimited transcriptional activation.
Publisher
Springer Science and Business Media LLC
Subject
Cell Biology,Molecular Biology,Biochemistry
Cited by
39 articles.
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