Genotoxic stress-induced nuclear localization of oncoprotein YB-1 in the absence of proteolytic processing

Abstract

Y-box-binding protein 1 (YB-1) is an oncogenic transcription factor whose overexpression and nuclear localization is associated with tumor progression and drug resistance. Transcriptional activation of YB-1 in response to genotoxic stress is believed to occur in the cytoplasm through sequence-specific endoproteolytic cleavage by the 20S Proteasome, followed by nuclear translocation of cleaved YB-1. To study the proteolysis model, we developed a two-step affinity purification of endogenous YB-1 protein species and characterized the products using mass spectrometry. Whereas full-length YB-1 was readily identified, the smaller protein band thought to be activated YB-1 was identified as hnRNP A1. An antibody specific for YB-1 was generated, which revealed only one YB-1 species, even after genotoxic stress-induced nuclear YB-1 translocation. These findings warrant re-evaluation of the mechanism of YB-1 nuclear translocation and transcriptional activation. The relationship between nuclear YB-1 and tumor progression may also have to re-evaluated in some cases.

The Role of the Y Box Binding Protein 1 C-Terminal Domain in Vascular Endothelial Cell Proliferation, Apoptosis, and Angiogenesis

“…The complex structure of YB1 allows it to participate in a wide variety of cellular functions, including transcriptional regulation, translational regulation, DNA repair, stress responses to extracellular signals, and drug resistance (Wu et al, 2007(Wu et al, , 2014Cohen et al, 2010;Kim et al, 2013;Zhao et al, 2013). Our previous data demonstrated that YB1 regulates gene transcription by binding the GC box sequences in the promoters of Klf4, SM22a, p21, and cyclin D1 (Shi et al, 2013).…”

Clusterin Is a Critical Downstream Mediator of Stress-Induced YB-1 Transactivation in Prostate Cancer

“…Stresses linked to activation of YB-1 include genotoxic stress with radiation (41,42) and cisplatin (43) as well as paclitaxel (26,28). In this study, we show that ER stress associated with paclitaxel, proteasome inhibition, or Hsp90 inhibition led to YB-1 nuclear translocation.…”

Multidrug Resistance-associated Protein-1 (MRP-1)-dependent Glutathione Disulfide (GSSG) Efflux as a Critical Survival Factor for Oxidant-enriched Tumorigenic Endothelial Cells

“…Supported by NLS, YB-1 is a transcription factor that is known to translocate to the nucleus under conditions of genotoxic stress (48). In cooperation with Ape/Ref-1, YB-1 drives the expression of mdr-1, closely related to MRP-1.…”