Mast cells are critical effectors of allergic inflammation and protection against parasitic infections. We previously demonstrated that transcription factors GATA2 and MITF are the mast cell lineage-determining factors. However, it is unclear whether these lineage-determining factors regulate chromatin accessibility at mast cell enhancer regions. In this study, we demonstrate that GATA2 promotes chromatin accessibility at the super-enhancers of mast cell identity genes and primes both typical and super-enhancers at genes that respond to antigenic stimulation. We find that the number and densities of GATA2- but not MITF-bound sites at the super-enhancers are several folds higher than that at the typical enhancers. Our studies reveal that GATA2 promotes robust gene transcription to maintain mast cell identity and respond to antigenic stimulation by binding to super-enhancer regions with dense GATA2 binding sites available at key mast cell genes.

Fowl adenovirus serotype 4 (FAdV-4) causes hepatitis-hydropericardium syndrome (HHS), leading to severe economic losses in the poultry industry. Although the pathogenesis of FAdV-4 infection has caused much attention, the underlying molecular mechanisms remain poorly understood. Here, we identified chaperonin containing TCP-1 subunit eta (CCT7) as an interacting partner of the FAdV-4 capsid protein hexon. We found that ectopic expression of CCT7 in leghorn male hepatocellular (LMH) cells enhanced hexon expression in pRK5-flag-hexon transfected cells. On the contrary, knockdown of cellular CCT7 by RNAi markedly reduced hexon expression in FAdV-4-infected cells and suppressed viral replication. These data suggest that CCT7 is required for FAdV-4 replication and may serve as a potential target for controlling FAdV-4 infection.

Macrophages play a critical role in inflammatory responses during infections. These cells are activated by infections through stimulation of TLRs expressed on their cell surface and produce pro-inflammatory cytokines, including TNF. However, distal enhancers that regulate TNF gene transcription in human macrophages have not been investigated. This study used an unbiased genomic approach to identify six candidate enhancers in human primary alveolar macrophages within a 131 kb region from the transcription start site (TSS) of the TNF gene, covering 13 genes. Of these candidate enhancers, five showed enhancer activity, with three targeting the TNF gene and two targeting neighboring genes. Deletion of the distal TNF E-16 enhancer led to a 73% reduction in TNF gene transcription in response to poly (I:C) stimulation in the THP-1 human leukemia monocytic cell line. Additionally, deletion of the E-7.1/hHS-8 enhancer resulted in a 41% reduction in TNF mRNA, while deletion of the PE enhancer had a lesser effect, resulting in a 52% reduction in TNF gene transcription. Massively parallel reporter assays (MPRA) indicated that the transcription factor AP-1 and EGR1-binding sites at the distal TNF E-16 enhancer were crucial in mediating enhancer activity. This study shows that both distal and proximal enhancers work together to fully transcribe the TNF gene in human macrophages in response to TLR ligand poly (I:C) stimulation.

Background: Histamine is a critical mediator of anaphylaxis, a neurotransmitter, and a regulator of gastric acid secretion. Histidine decarboxylase is a rate-limiting enzyme for histamine synthesis. However, in vivo regulation of Hdc, the gene that encodes histidine decarboxylase is poorly understood. Objective: We sought to investigate how enhancers regulate Hdc gene transcription and histamine synthesis in resting conditions and in a mouse model of anaphylaxis. Methods: H3K27 acetylation histone modification and chromatin accessibility were used to identify candidate enhancers; The enhancer activity of candidate enhancers was measured in a reporter gene assay; and the function enhancers were validated using CRISPR deletion. Results: Deletion of the GC box, which binds to zinc finger transcription factors, in the proximal Hdc enhancer, reduced Hdc gene transcription and histamine synthesis in the mouse and human mast cell lines. Mast cells, basophils, brain cells, and stomach cells from GC box-deficient mice transcribed the Hdc gene much less than similar cells from wild-type mice and Hdc GC box-deficient mice failed to develop anaphylaxis. Conclusion: Our results demonstrate that the HDC GC box within the proximal enhancer in the mouse and human HDC gene is essential for Hdc gene transcription, histamine synthesis, and histamine-mediated anaphylaxis in vitro and in vivo.