A mutation in a functional Sp1 binding site of the telomerase RNA gene (hTERC) promoter in a patient with Paroxysmal Nocturnal Haemoglobinuria

We searched for mutations in DNA extracted from PNH patients by amplification of the hTERC gene and denaturing high performance liquid chromatography (dHPLC). After a mutation was found in a potential transcription factor binding site in one patient electrophoretic mobility shift assays were used to detect binding of transcription factors to that site. The effect of the mutation on the function of the promoter was tested by transient transfection constructs in which the promoter is used to drive a reporter gene.Here we report the finding of a novel promoter mutation (-99C->G) in the hTERC gene in a patient with PNH. The mutation disrupts an Sp1 binding site and destroys its ability to bind Sp1. Transient transfection assays show that mutations in this hTERC site including C-99G cause either up- or down-regulation of promoter activity and suggest that the site regulates core promoter activity in a context dependent manner in cancer cells.These data are the first report of an hTERC promoter mutation from a patient sample which can modulate core promoter activity in vitro, raising the possibility that the mutation may affect the transcription of the gene in hematopoietic stem cells in vivo, and that dysregulation of telomerase may play a role in the development of bone marrow failure and the evolution of PNH clones.Dyskeratosis congenita is an inherited bone marrow failure syndrome whose characteristic features are nail dystrophy, abnormal skin pigmentation and mucosal leucoplakia [1]. There are X-linked, autosomal dominant and recessive forms of the disease. The X-linked form is due to mutations in the gene, DKC1, which codes for the nucleolar protein dyskerin [2]. Dyskerin is a component of snoRNP complexes involved in rRNA maturation [3] and is also associated with the telomerase complex [4]. Autosomal dominant DC is due to mutations in the gene, hTERC [5] encoding the telomerase RNA component, suggesting the pathology of DC is largely due to defective telomerase. T