Regulation of Human Acetylcholinesterase Gene Expression

Abstract

Acetylcholinesterase (AChE) in human cells is encoded by a single gene, ACHE, located on chromosome 7q22. We have investigated the transcriptional regulation of ACHE by defining the mRNA cap sites and characterizing essential promoter and enhancer elements. We find putative promoter elements reside immediately upstream of the first untranslated exon, and are characterized by GC rich sequences containing consensus binding sites for transcription factors SP1, EGR-1 and AP-2. In vitro transcription studies and RNase protection of mRNA from human NT2/D1 teratocarcinoma cells reveal two closely spaced transcription cap sites. Both cap sites are located at a consensus initiator element similar to the terminal transferase gene initiator element. Transient transfection experiments show removal of three bases of this initiator sequence reduce promoter activity 98% in NT2/D1 cells. In vitro transcription and transient transfection of a series of ACHE promoter 5’ deletion mutants linked to a luciferase reporter show one SP1 site at −70 is essential for promoter activity. Purified recombinant SP1 protein protects this site in DNase footprinting experiments. Footprinting also shows purified recombinant transcription factor AP-2 binds 17 base pairs upstream of the initiator element. In vitro transcription studies with AP-2 protein and transient co-transfection of wild type AP-2 cDNA with ACHE promoter-luciferase reporter constructs show AP-2 functions as a repressor of A CHE transcription. Retinoic acid treatment of NT2/D1 cells induces AChE enzyme activity greater than 30 fold and mRNA levels 50 fold, while the rate of gene transcription remains unchanged. These data indicate ACHE transcription is activated by SP1 or similar factors, AP-2 represses ACHE transcription in vitro, and mRNA levels are controlled by changes in mRNA stability. (Supported by USPHS GM18360).