title: A novel DNA-binding protein, PhaR, plays a central role in the regulation of polyhydroxyalkanoate accumulation and granule formation in the haloarchaeon Haloferax mediterranei.
abstract: Polyhydroxyalkanoates (PHAs) are synthesized and assembled as PHA granules that undergo well-regulated formation in many microorganisms. However, this regulation remains unclear in haloarchaea. In this study, we identified a PHA granule-associated regulator (PhaR) that negatively regulates the expression of both its own gene and the granule structural gene phaP in the same operon (phaRP) in Haloferax mediterranei. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) assays demonstrated a significant interaction between PhaR and the phaRP promoter in vivo. Scanning mutagenesis of the phaRP promoter revealed a specific cis-element as the possible binding position of the PhaR. The haloarchaeal homologs of the PhaR contain a novel conserved domain that belongs to a swapped-hairpin barrel fold family found in AbrB-like proteins. Amino acid substitution indicated that this AbrB-like domain is critical for the repression activity of PhaR. In addition, the phaRP promoter had a weaker activity in the PHA-negative strains, implying a function of the PHA granules in titration of the PhaR. Moreover, the H. mediterranei strain lacking phaR was deficient in PHA accumulation and produced granules with irregular shapes. Interestingly, the PhaR itself can promote PHA synthesis and granule formation in a PhaP-independent manner. Collectively, our results demonstrated that the haloarchaeal PhaR is a novel bifunctional protein that plays the central role in the regulation of PHA accumulation and granule formation in H. mediterranei.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Shuangfeng
authors.initials: S
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Dahe
authors.initials: D
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Guiming
authors.initials: G
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Han
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China University of Chinese Academy of Sciences, Beijing, People's Republic of China xiangh@im.ac.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Xiang
mesh_terms: D047369:Chromatin Immunoprecipitation; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019848:Gene Expression Regulation, Archaeal; D019623:Haloferax mediterranei / Q000378:metabolism* / Q000648:ultrastructure*; D054813:Polyhydroxyalkanoates / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D004268:DNA-Binding Proteins; D054813:Polyhydroxyalkanoates