Molecular cloning and expression analysis of human glycogen synthase kinase-3α promoter

Human glycogen synthase kinase-3α (GSK-3α) is a serine/threonine kinase that phosphorylates a variety of cytoplasmic and nuclear proteins. It also phosphorylates components of the neuronal cytoskeleton including tau and neurofilament heavy chain. Hyperphosphorylated tau is found in neurofibrillary tangles, a hallmark of Alzheimer’s disease and aberrant phosphorylation of neurofilament heavy chain is observed in motor neuron disease. Alterations in GSK-3α activity may therefore contribute to the disease process in these disorders. As a first step to understand the transcriptional regulation of GSK-3α, a 2-kb (p-1751/+243) DNA fragment upstream of the GSK-3α initiation codon was obtained from a YAC clone and characterised. Using primer extension assays, a putative transcriptional start site was located to a G nucleotide 244 bp upstream of the ATG codon. Several transcription factor-binding sites were identified on the promoter region, but no TATA-like element was located close to the start site. Deletion mutants of the 2-kb DNA fragment were generated and fused to a promoterless chloramphenicol acetyltransferase (CAT) gene. Transfection study in a neuroblastoma cell line revealed the 1-kb (p-719/+243) fragment carried strong promoter activity, while the 2-kb construct that contains an Alu-like sequence was only 50% active.