BACKGROUND: Mutations in the gene coding for the
RNA component of
telomerase,
hTERC, have been found in
autosomal dominant dyskeratosis congenita (DC) and
aplastic anemia.
Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal blood disorder associated with
aplastic anemia and characterized by the presence of one or more clones of blood cells lacking
glycosylphosphatidylinositol (
GPI) anchored proteins due to a somatic mutation in the PIGA gene. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.