#6741 TRANSCRIPTION FACTOR ATF3 EXACERBATES RENAL FIBROSIS THROUGH RECRUITING HISTONE ACETYLASES
Authors: Yang Lina , Chen Yilong , Fu Ping , MA Liang , Yu Haopeng 
Published: June 2023

Abstract

Background and Aims
Chronic kidney disease (CKD) threatens public health around the world. Renal fibrosis is a final common pathology in renal diseases of different etiologies. However, no efficient, broadly applicable anti-fibrotic therapies exist. Histone acetylation is an epigenetic modification involved in the regulation of multiple disease-specific gene expressions, balanced by histone acetyltransferases and histone deacetylase (HDAC) enzymes. Transcription factors (TF) could recruit histone-modifying enzymes and alter gene expression. But now, much remains unknown about the role of histone acetylation and whether there exits the regulator of it in fibrosis of CKD. Here, we for the first time explored a novel aspect of ATF3 promoting kidney fibrosis via recruiting the histone acetylases to fibrosis-related genes in CKD.

Method
We constructed a CKD mouse model by using adenine and oxonate. Serum were taken for the measurement of BUN and creatinine. Kidneys were harvested and processed for histological, sequencing, qRT-PCR, and western blotting analysis. RNA-seq and ChIP-seq (antibody: H3K27ac) of mouse kidneys were conducted for profiling the differential gene expression and H3K27ac. GO and KEGG analysis was performed for annotation of the function. Motif analysis was applied for searching the regulator of H3K27ac. Biopsy samples of patients with common CKD were used for immunohistochemical analysis. ATF3-KO mice were also conducted for defining the function of ATF3 in CKD. To profile the ATF3 binding site on chromatin, ChIP-seq of ATF3 in mice kidneys of normal control and CKD were also performed. Besides, the data contained ATF3 interact protein in databases (ChIP-atlas and BioGrid) and the results of protein interaction prediction were integrated for finding the protein-protein interaction of ATF3. TGF-β- stimulated TCMK-1 cell served as the cell model for further mechanism validation. CO-IP in cells clarifies that ATF3 could recruit the histone acetyltransferases. ChIP-qPCR of the fibrosis gene was performed to further verify the mechanism of ATF3-regulated gene expression.

Results
Firstly, compared with the normal control, histone modification H3K27ac repertoire was changed in chronic kidney disease. 11859 H3K27ac peaks specific to CKD, and 14996 H3K27ac peaks specific to healthy mice kidneys were found. The binding intensity of these regions has altered dramatically in the kidney of CKD. Pearson correlation analysis and function annotation showed that CKD-specific changes of H3K27ac were associated with fibrosis gene expression. Motif analysis showed that ATF3 in the top 10 TFs that may interact with H3K27ac. Among those TFs, ATF3 elicited the highest expression. Besides, ATF3 could co-localize with H3K27ac along the mice genome globally. By immunohistochemical staining analysis, we observed the upregulation of ATF3 in the kidneys of patients with biopsy-proven CKD. We found that knocking out the ATF3 could significantly reduce kidney damage in CKD mice. In parallel with improved morphological injuries, the level of kidney fibrosis gene expression was also significantly reduced in ATF3–/– mice. Furthermore, the H3K27ac on the mice chromatin altered along with the knockout of ATF3, and several fibrosis-related gene expressions which elevated in CKD were decreased by deficiency of ATF3. On the region of gene cd2, H3K27ac disappeared with the knockout of ATF3 in CKD. We found that ATF3 could interact with histone acetyltransferases (CBP, KAT7, P300) to promote the H3K27ac. Further evidenced by ChIP-qPCR of fibrosis gene cd2, we found that ATF3 could recruit the histone acetyltransferases on the fibrosis gene to promote the H3K27ac to provoke the gene expression in the cell model.

Conclusion
We profiled the landscape of H3K27ac in CKD, explored the epigenetic regulator of H3K27ac, and revealed that ATF3 promotes renal fibrosis in CKD. Notably, we for the first time explored a novel mechanism of ATF3 about recruiting histone acetyltransferases to regulate the H3K27ac on fibrosis gene. Our data highlighted that ATF3 might represent a potential therapeutic target against fibrotic kidney diseases.