Livin Regulates H2A.XY142 Phosphorylation and Promotes Autophagy in Colon Cancer Cells via a Novel Kinase Activity.

Yang Ge,Shu-Qiang Li,Jun-Peng Cui,Bao-Lin Liu

doi:10.3389/fonc.2019.01233

Abstract

Objective: To investigate Livin-mediated regulation of H2A.XY142 phosphorylation via a novel kinase activity and its effect on autophagy in colon cancer cells.Methods: The interaction between Livin and H2A.X was tested by immunoprecipitation. H2A.X–/– HCT116 cells were transfected with human influenza hemagglutinin (HA)-tagged WT or Y142F phospho-dead mutantH2A.X plasmids. GST-tagged recombinant Livin protein was used to perform in vitro pull-down experiment and kinase assay. H2A.X–/–Livin+/+ SW480 cells were co-transfected with H2A.XWT/H2A.XY142F plasmid and LC3 EGFP-tagged plasmid to explore whether H2A.XY142F was involved in Livin-mediated autophagy induced by starvation in colon cancer cells.Results: Co-immunoprecipitation studies confirmed that Livin interacted with H2A.X and that it was phosphorylation dependent. In vitro kinase assay confirmed that Livin could phosphorylate H2A.X. Knockdown of Livin (Livin–/–) in SW480 cells or HCT116 cells canceled the starvation-induced autophagy in colon cancer cells; H2A.X–/–Livin+/+ SW480 cells transfected with H2A.XWT activated autophagy induced by starvation while cells transfected with H2A.XY142F had no significant difference; Livin-H2A.XY142F axis activated autophagy in colon cancer cells through transcriptionally regulating ATG5 and ATG7.Conclusion: Livin promotes autophagy in colon cancer cells via regulating the phosphorylation of H2A.XY142.

Highlights

The nucleosome is a structure composed of a about 200 bp DNA molecule coiling outside and a histone octamer in the core, which is a basic structural unit of the chromosome
We investigated the effect of Livin on cellular autophagy in colon cancer cells and its potential role as a kinase regulating H2A.XY142 phosphorylation
We found that the levels of Livin in HT-29 cells and SW480 cells were obviously higher compared to HCT116 cells (Figure 1A)

Summary

Introduction

The nucleosome is a structure composed of a about 200 bp DNA molecule coiling outside and a histone octamer in the core, which is a basic structural unit of the chromosome. Multiple post-translational modifications, inclusive of phosphorylation, acetylation, methylation, and ubiquitination, of core histone proteins have been indicated to regulate histone modification and multitude of cellular functions [2,3,4,5]. Livin Affects Colon-Cancer Cellular Autophagy phosphorylation of H3 at tyrosine 41 (H3 Y41) is important in carcinogenic pathways [7]—highlighting the importance of tyrosine phosphorylation of core histone proteins as a key regulatory mechanism. Inhibition of apoptosis is considered as one of the cardinal requirements of cancer cells to survive and propagate [8]. Livin can degrade secondary mitochondria derived activation of caspase (Smae), which is a novel mitochondrial protein, preventing its antagonism to IAPs and indirectly inhibiting caspases to delay normal cell apoptosis [10]. Livin protein is mainly expressed in the cytoplasm in cancer cells. Overexpression of Livin can modulate resistance to chemotherapy or radiotherapy in colon cancer [12]

Methods

Results

Conclusion