Submitted April 10, 2007
Accepted November 20, 2007
A dyskerin motif reactivates telomerase activity in X-linked dyskeratosis congenita and in telomerase deficient human cells
Rosario Machado-Pinilla, Isabel Sanchez-Perez, Jose Ramon Murguia, Leandro Sastre, and Rosario Perona*
Translational Oncology Unit, Instituto de Investigaciones Biomedicas CSIC/UAM, Madrid, Spain
Institute of Plant Molecular and Cellular Biology, Universidad Politecnica de Valencia, Valencia, Spain
Department of Control of Gene Expression Regulation, Instituto de Investigaciones Biomedicas, CSIC/UAM, Madrid, Spain
* Corresponding author; email: rperona{at}iib.uam.es.
Dyskerin gene is mutated in X-linked dyskeratosis congenita patients (X-DC) which results in greatly reduced levels of telomerase activity. A genetic suppressor element (GSE) termed GSE24-2 has been isolated in a screening for cisplatin resistance. GSE24-2 expressing cells presented impaired telomerase inhibition following in vitro exposure to chemotherapies, such as cisplatin, or telomerase inhibitors. The promoter of the telomerase component hTERT, was constitutively activated in GSE24-2 cells in a c-myc expression-dependent manner. Deletion analyses and mutagenesis of the human c-myc promoter demonstrated that the target sequence for activation was the NHEIII site located upstream to the P1 region of the promoter. Further, expression of GSE24-2 in cell lines derived from X-DC patients and in VA13 cells induced increased hTERT RNA and hTR levels and recovery of telomerase activity. Finally, expression of GSE24-2 was able to rescue X-DC fibroblasts from premature senescence. These data demonstrate that this domain of dyskerin plays an important role in telomerase maintenance following cell insults such as cisplatin treatment, and in telomerase-defective cells in patients with X-DC. The expression of this dyskerin fragment has a dominant function in X-DC cells and could provide the basis for a therapeutic approach to this disease.
