Figure 3.

The LDLR promoter regulation.

Notes: Low-density lipoprotein receptor gene (LDLR) 5′ promoter region of 300 bp is represented, numbered the A of the ATG codon as +1. The major regulatory regions are indicated with different colors: FP2 (from −280 to −268); FP1 (−238 to −217); repeat (REP) 1 (−196 to −181); REP 2 (−161 to −146); REP 3 (−145 to −128); and TATA box (from −116 to −110 and −107 to −101). Interaction between cis-element and trans-element at the proximal promoter drives high levels transcription when sterol level becomes deficient. The sterol regulatory element (SRE) binding protein transcription factor interacts with the SRE-1 of REP 2, whereas SP1 transcription factors interact with REP 1 and REP 3 to promoter high levels of LDLR gene transcription in response to low intracellular sterol concentrations. SP1 also involved with constitutive, basal-level expression of the LDLR gene. The TATA boxes recruit and direct the assembly of general transcription factors at the promoter.