RBP4-BACH1 Interaction Modulates Transcriptional Regulation of Insulin Signaling Pathway Genes

Abstract

Retinol-binding protein 4 (RBP4) exhibits diurnal oscillatory pattern and is elevated under conditions of circadian disruption and in type 2 diabetes mellitus, yet the molecular link between RBP4 and impaired glucose metabolism remains elusive. Here, we overexpressed RBP4 in human hepatoma Huh7 cells and performed integrated RNA sequencing (RNA-seq), Co-immunoprecipitation (Co-IP) coupled with mass spectrometry (MS), and Cleavage Under Targets and Tagmentation (CUT&Tag). We identified BACH1 as a direct RBP4-interacting transcription factor that predominantly binds the TGACTCA motif in promoter regions of genes involved in carbon metabolism pathways. Integrative analysis of RNA-seq and CUT&Tag data uncovered 63 direct target genes co-regulated by RBP4 and BACH1, including known circadian and metabolic regulators SLC7A11, PFKFB3, CTCF, NR1D2 and WEE1 as well as novel candidates SF1 and PIN1. These target genes are significantly enriched in insulin receptor signaling and carbohydrate metabolic pathways. Mechanistically, the RBP4-BACH1 axis reprograms glucose metabolism, linking circadian rhythm disturbances to dysregulated glucose homeostasis. Collectively, our findings establish a functional role for RBP4 in connecting circadian disruption to diabetes and highlight RBP4 as a potential therapeutic target.