Identification and Molecular Characterization of HOS15-interacting Proteins in Arabidopsis thaliana

Chromatin modification is a key mechanism of gene expression in eukaryotes, and involve interactions among several proteins. Recently, we reported that HOS15, a cullin-based E3 ligase receptor, is involved in chromatin remodeling, and regulates gene expression and cold tolerance in Arabidopsis thaliana. To identify the protein complexes that function in conjunction with HOS15, we performed FLAGtag affinity purification using transgenic Arabidopsis plants expressing HOS15-FLAG, and isolated HOS15-interacting proteins. To identify these proteins, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) analysis was conducted, and 16 proteins were identified. Database searches revealed that these proteins were histone variants, histone deacetylases, mRNA splicing regulators, a protein kinase, and proteins of unknown function. The ability of these proteins binding to HOS15 was confirmed using yeast two-hybrid, co-immunoprecipitation (Co-IP), and luciferase complementation imaging (LCI) assays. Our data suggest that specific interactions between HOS15 and those proteins involve in chromatin remodeling and RNA processing regulates plant development and abiotic stress in Arabidopsis.