Investigation The BZIP Domain Transcription Factor CPC-1 Mediated Chromatin Modification In The Regulation Of Cat-3 Gene Expression In Neurospora Crassa

Reactive oxygen species(ROS),which are produced through electron transport chain during endogenous and extracellular redox reaction in cells.Previous studies have shown that ROS are formed as natural byproducts during the normal redox reactions.These ROS have pivotal roles in cell signal transduction and homeostasis.They also play an important function in regulating gene regulation and phase transitions of cell cycle.However,the ROS may also pose a serious threat to cells if the intracellular ROS levels deviate from the optimal amount.Therefore,the amount of ROS within the cells keeps a balance between produce and clear up processes.Once the ROS homeostasis is disrupted,its negative effects are released.For most of aerobic eukaryotic organisms,one of the most important steps to defense ROS attack is transfer the ROS into other substances that are harmless to the cells,such as the operations of SOD(superoxide dismutase)and catalase.SOD can alternately catalyze the decompose of the superoxide radical into hydrogen peroxide,and then the hydrogen peroxide is degraded and converted into H20 and O2 by catalases.The accurate maintance of ROS equilibration plays an important role in cell development and differentiation.Thus,SOD and catalase are essential for aerobic organisms to adapt the changing environment and defense stress conditions.Filamentous fungus Neurospora is an important model organism.The N.crassa has been identified with three catalases,including CAT-1,CAT-2 and CAT-3.The expression profiles of these catalases are rigorously regulated due to its vital role in mycelia growth development and morphogenetic transition.Recently,our study revealed that cat-3 gene expression responds to the H2O2 stress and its expression level and the H3 acetylation at its locus are significantly increased after H2O2 treatment.However,the mechanism of cat-3 gene expression and its ability to response to the H2O2 stress are not clear.Here we show that the cross-pathway control gene cpc-1 and histone acetyltransferase GCN5 play valuable fuctions in the regulation of cat-3 gene expression in N.crassa.We screened the histone acetyltransferase mutant strains and confirmed that the histone acetyltransferases GCN5 is responsible for histone acetylation in the cat-3 gene expression under stress condition.The expression of CAT-3 in the gcn5KO strain was extremely reduced compared to those in wild-type strains,and its expression cannot be induced with H2O2 treatment.Furthermore,we also identified the bZIP domain transcription factor CPC1 as a key transcription factor of cat-3 gene,the cat-3 expression levels is significantly decreased and cannot be induced upon H2O2 treatment in cpc-1(j-5)mutant.During the conidia germination,the expression profile of CPC1 and CAT-3 displayed a similar pattern and their expression levels are increased to a same enrichment upon H2O2 treatment,which suggesting that CPC1 is correlated with CAT-3 expression.We also constructed the cpc-1(j-5)nap1KO double mutants,the CAT-3 protein levels were extremely low and cannot be induced by H2O2 treatment in the double mutants.The phonotype of double mutant was similar to those in cpc-1(j-5)single mutants,indicating that CPC1 is the key transcription factor for CAT-3 expression upon stress condition.The N.crassa CPC1 is the homolog of yeast GCN4,our ChIP assays data declared that the CPC1 directly targets the cat-3 promoter region and its binding is strengthened upon H2O2 treatment.Our findings provide a new evidence of CPC1 and GCN5 in activating cat-3 transcription.These results disclosed a distinctive function of CPC1 at the regulatory pathway for cat-3 transcription,which is mediated by GCN5-dependent acetylation.