β-Catenin interacts with the TAZ1 and TAZ2 domains of CBP/p300 to activate gene transcription

Mechanism for controlled assembly of transcriptional condensates by Aire

Transcriptional condensates play a crucial role in gene expression and regulation, yet their assembly mechanisms remain poorly understood. Here, we report a multi-layered mechanism for condensate assembly by autoimmune regulator (Aire), an essential transcriptional regulator that orchestrates gene expression reprogramming for central T cell tolerance. Aire condensates assemble on enhancers, stimulating local transcriptional activities and connecting disparate inter-chromosomal loci. This functional condensate formation hinges upon the coordination between three Aire domains: polymerization domain caspase activation recruitment domain (CARD), histone-binding domain (first plant homeodomain (PHD1)), and C-terminal tail (CTT). Specifically, CTT binds coactivators CBP/p300, recruiting Aire to CBP/p300-rich enhancers and promoting CARD-mediated condensate assembly. Conversely, PHD1 binds to the ubiquitous histone mark H3K4me0, keeping Aire dispersed throughout the genome until Aire nucleates on enhancers. Our findings showed that the balance between PHD1-mediated suppression and CTT-mediated stimulation of Aire polymerization is crucial to form transcriptionally active condensates at target sites, providing new insights into controlled polymerization of transcriptional regulators.

The winged helix domain of MORF binds CpG islands and the TAZ2 domain of p300

Acetylation of histones by lysine acetyltransferases (KATs) provides a fundamental mechanism by which chromatin structure and transcriptional programs are regulated. Here, we describe a dual binding activity of the first winged helix domain of human MORF KAT (MORFWH1) that recognizes the TAZ2 domain of p300 KAT (p300TAZ2) and CpG rich DNA sequences. Structural and biochemical studies identified distinct DNA and p300TAZ2 binding sites, allowing MORFWH1 to independently engage either ligand. Genomic data show that MORF/MOZWH1 colocalizes with H3K18ac, a product of enzymatic activity of p300, on CpG rich promoters of target genes. Our findings suggest a functional cooperation of MORF and p300 KATs in transcriptional regulation.

BARX1 repressed FOXF1 expression and activated Wnt/β-catenin signaling pathway to drive lung adenocarcinoma

BACKGROUND

Underlying molecular mechanisms of BARX homeobox 1 (BARX1) in lung adenocarcinoma (LUAD) remain elusive.

METHODS

Abnormally expressed genes in LUAD tissues were analyzed by RNA-sequencing. CCK-8, colony formation, transwell, and wound healing assays examined proliferation, colony formation, invasion, and migration of LUAD cells, respectively. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay examined the interaction between BARX1 and Forkhead Box F1 (FOXF1). Xenograft mouse model of LUAD was constructed to monitor the growth and metastasis of tumor.

RESULTS

BARX1 was upregulated, FOXF1 was downregulated in LUAD tissues and cells. There was a negative correlation between BARX1 and FOXF1 expression. BARX1 deficiency limited malignant phenotypes of LUAD cells, including proliferation, invasion, migration and EMT. In vivo, BARX1 knockdown suppressed tumor growth and metastasis in A549-drove xenograft mouse model. BARX1 interacted with FOXF1 promoter and repressed FOXF1 expression. Upregulation of BARX1 promoted the expression of Wnt5a, β-catenin, and phosphorylated-glycogen synthase kinase-3 beta (p-GSK3β), whereas inhibited FOXF1, p-β-catenin, and GSK3β in LUAD cells. BARX1 knockdown caused an opposite result. Rescue assays uncovered that FOXF1 reversed the impact of BARX1 on malignant phenotypes and Wnt/β-catenin of LUAD cells.

CONCLUSION

BARX1 repressed FOXF1 expression and activated Wnt/β-catenin signaling pathway to drive lung adenocarcinoma.