title: Expression and chromatin structures of cellulolytic enzyme gene regulated by heterochromatin protein 1.
abstract: BACKGROUND
  Heterochromatin protein 1 (HP1, homologue HepA inPenicillium oxalicum) binding is associated with a highly compact chromatin state accompanied by gene silencing or repression. HP1 loss leads to the derepression of gene expression. We investigated HepA roles in regulating cellulolytic enzyme gene expression, as an increasingly number of studies have suggested that cellulolytic enzyme gene expression is not only regulated by transcription factors, but is also affected by the chromatin status.
  
  
  RESULTS
  Among the genes that exhibited significant differences between thehepAdeletion strain (ΔhepA) and the wild type (WT), most (95.0 %) were upregulated in ΔhepAcompared with WT. The expression of the key transcription factor for cellulolytic enzyme gene (e.g., repressor CreA and activator ClrB) increased significantly. However, the deletion ofhepAled to downregulation of prominent extracellular cellulolytic enzyme genes. Among the top 10 extracellular glycoside hydrolases (Amy15A, Amy13A, Cel7A/CBHI, Cel61A, Chi18A, Cel3A/BGLI, Xyn10A, Cel7B/EGI, Cel5B/EGII, and Cel6A/CBHII), in which secretion amount is from the highest to the tenth inP.oxalicumsecretome, eight genes, including two amylase genes (amy15Aandamy13A), all five cellulase genes (cel7A/cbh1,cel6A/cbh2,cel7B/eg1,cel5B/eg2, andcel3A/bgl1), and the cellulose-active LPMO gene (cel61A) expression were downregulated. Results of chromatin accessibility real-time PCR (CHART-PCR) showed that the chromatin of all three tested upstream regions opened specifically because of the deletion ofhepAin the case of two prominent cellulase genescel7A/cbh1andcel7B/eg1. However, the open chromatin status did not occur along with the activation of cellulolytic enzyme gene expression. The overexpression ofhepAupregulated the cellulolytic enzyme gene expression without chromatin modification. The overexpression ofhepAremarkably activated the cellulolytic enzyme synthesis, not only in WT (~150 % filter paper activity (FPA) increase), but also in the industry strain RE-10 (~20-30 % FPA increase).
  
  
  CONCLUSIONS
  HepA is required for chromatin condensation of prominent cellulase genes. However, the opening of chromatin mediated by the deletion ofhepAwas not positively correlated with cellulolytic enzyme gene activation. HepA is actually a positive regulator for cellulolytic enzyme gene expression and could be a promising target for genetic modification to improve cellulolytic enzyme synthesis.
authors.affiliation: National Glycoengineering Research Center and State Key Lab of Microbial Technology, Shandong University, Jinan, 250100 China ; Shandong Provincial Key Laboratory of Carbohydrate Chemistry and Glycobiology, Shandong University, Jinan, 250100 China.
authors.forename: Xiujun
authors.initials: X
authors.lastname: Zhang
authors.affiliation: National Glycoengineering Research Center and State Key Lab of Microbial Technology, Shandong University, Jinan, 250100 China.
authors.forename: Yinbo
authors.initials: Y
authors.lastname: Qu
authors.affiliation: National Glycoengineering Research Center and State Key Lab of Microbial Technology, Shandong University, Jinan, 250100 China ; Shandong Provincial Key Laboratory of Carbohydrate Chemistry and Glycobiology, Shandong University, Jinan, 250100 China.
authors.forename: Yuqi
authors.identifier: 0000-0003-3766-9827
authors.initials: Y
authors.lastname: Qin
keywords: CHART-PCR; Cellulolytic enzyme; Chromatin; HP1; Penicillium oxalicum