Class E basic helix-loop-helix protein 40 (BHLHE40)

Class E basic helix-loop-helix protein 40 (BHLHE40, also known as DEC1, SHARP2, STRA13, and other aliases) is a transcription factor belonging to the basic helix-loop-helix (bHLH) family, characterized by a bHLH DNA-binding domain and an orange domain[1][4][5]. BHLHE40 regulates transcription by binding to E-box (CACGTG) sequences and acts primarily as a repressor of clock genes and clock-controlled genes, serving a central role in circadian rhythm regulation and functioning in a distinct autoregulatory feedback loop[3]. It is expressed in various tissues and regulates multiple biological processes, including cell differentiation, cell cycle progression, apoptosis, immune activation/modulation, adipogenesis, skeletal muscle regeneration, and neurogenesis[1][5][6]. BHLHE40 function is context-dependent; it may promote or suppress tumorigenesis in different cancer types, often responding to hypoxia and interacting with key cellular pathways, including PI3K/Akt/mTOR and STAT1 signaling[1][2]. Relevant in both diabetes and cancer, it is also induced by TGF-β and hypoxia signaling. The gene is located on chromosome 3p26.1 and can form homo- or heterodimers, especially with BHLHE41. BHLHE40's expression level and activity are biomarkers for cancer progression and grade, but the highly context-specific nature of its actions in disease means its targeting presents therapeutic challenges due to its dual tumor suppressor/promoter roles[1][2][3].

Other names

BHLHE40BHLHB2DEC1SHARP2STRA13SHARP-2Clast5Class B basic helix-loop-helix protein 2Differentially expressed in chondrocytes protein 1Differentiated embryo chondrocyte expressed gene 1Enhancer-of-split and hairy-related protein 2Stimulated by retinoic acid gene 13 proteinHLHB2Stra14