Critical Role for Cold Shock Protein YB-1 in Cytokinesis.

Sunali Mehta,Jessie Zhang,Tariq Al-Jabry,V Pragathi Masamsetti,Michael Algie,Torsten Kleffmann,Rhodri Harfoot,Puja Bhatia,Megan Chircop,Cushla Mckinney,Tara K Bartolec,Srinivasaraghavan Kannan,Kim H Parker ,Luke C Henderson ,Scott B Cohen ,Wenting Ma ,Chandra Verma ,Adele G Woolley ,Maree Gould ,Anthony J Cesare ,Antony W Braithwaite

doi:10.3390/cancers12092473

Abstract

Simple SummaryY-box-binding protein-1, YB-1, plays an important role in regulating the cell cycle, although precisely how it does the is unknown. Using live cell imaging, we show that YB-1 is essential for initiating the last step of cell division (cytokinesis), required for creation of two daughter cells. Using confocal microscopy we showed that YB-1 regulates the spatial distribution of key proteins essential for cytokinesis to occur and that this required YB-1 to be phosphorylated on several residues. In-silico modeling demonstrated that modifications at these residues resulted in conformational changes in YB-1 protein allowing it to interact with proteins essential for cytokinesis. As many cancers have high levels YB-1 and these are associated with poor prognosis, our data suggest developing small molecule inhibitors to block YB-1 phosphorylation could be a novel approach to cancer therapy.High levels of the cold shock protein Y-box-binding protein-1, YB-1, are tightly correlated with increased cell proliferation and progression. However, the precise mechanism by which YB-1 regulates proliferation is unknown. Here, we found that YB-1 depletion in several cancer cell lines and in immortalized fibroblasts resulted in cytokinesis failure and consequent multinucleation. Rescue experiments indicated that YB-1 was required for completion of cytokinesis. Using confocal imaging we found that YB-1 was essential for orchestrating the spatio-temporal distribution of the microtubules, β-actin and the chromosome passenger complex (CPC) to define the cleavage plane. We show that phosphorylation at six serine residues was essential for cytokinesis, of which novel sites were identified using mass spectrometry. Using atomistic modelling we show how phosphorylation at multiple sites alters YB-1 conformation, allowing it to interact with protein partners. Our results establish phosphorylated YB-1 as a critical regulator of cytokinesis, defining precisely how YB-1 regulates cell division.

Highlights

Y-box binding protein 1 (YB-1) is a multifunctional member of the cold-shock protein superfamily that plays an important role during development and cancer [1,2]
Cytokinesis failure resulted in significant accumulation of multinucleated cells over time (Figure 1d, Videos S1 and S2) and overexpression of YB-1EBFP2 along with shRNA targeting endogenous YB-1 -UTR (sh-YB-1) significantly decreased the number of multinucleated cells (Figure 1d)
We provide unequivocal evidence that defects in YB-1 result in cytokinesis failure and multinucleation in cancer cells

Summary

Introduction

Y-box binding protein 1 (YB-1) is a multifunctional member of the cold-shock protein superfamily that plays an important role during development and cancer [1,2]. YB-1 is required for continued cell proliferation in vivo, reviewed in [1], and YB-1 overexpression in transgenic mice led to the development of invasive breast cancer in all instances [7]. Reducing YB-1 levels in tumour xenograft models of breast, brain, lung and pharyngeal cancers inhibited cell proliferation [4,8,9]. YB-1 has been shown to disable the p53 pathway to allow continued cellular propagation despite genomic insult [19]. In addition to these studies, overexpression of YB-1 has been shown to result in cell division errors [20]. Consistent with damage tolerance, YB-1 promotes chemotherapy resistance [12,21,22,23]

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