title: The accumulation and not the specific activity of telomerase ribonucleoprotein determines telomere maintenance deficiency in X-linked dyskeratosis congenita.
abstract: X-linked dyskeratosis congenita (X-DC) is caused by mutations in the housekeeping nucleolar protein dyskerin. Amino acid changes associated with X-DC are remarkably heterogeneous. Peripheral mononuclear blood cells and fibroblasts isolated from X-DC patients harbor lower steady-state telomerase RNA (TER) levels and shorter telomeres than healthy age-matched controls. Previously, we showed that retroviral expression of recombinant TER, together with expression of recombinant telomerase reverse transcriptase, restored telomere maintenance and proliferative capacity in X-DC patient cells. Using rare X-DC isoforms (ΔL37 and A386T dyskerin), we showed that telomere maintenance defects observed in X-DC are solely due to decreased steady-state levels of TER. Disease-associated reductions in steady-state TER levels cause deficiencies in telomere maintenance. Here, we confirm these findings in other primary X-DC patient cell lines coding for the most common (A353V dyskerin) and more clinically severe (K314R and A353V dyskerin) X-DC isoforms. Using cell lines derived from these patients, we also examined the steady-state levels of other hinge-ACA motif RNAs and did not find differences in their in vivo accumulations. We show, for the first time, that purified telomerase holoenzyme complexes from different X-DC cells have normal catalytic activity. Our data confirm that dyskerin promotes TER stability in vivo, endorsing the development of TER supplementation strategies for the treatment of X-DC.
authors: University of British Columbia, Vancouver, BC, Canada.
authors: Xi-Lei
authors: XL
authors: Zeng
authors: Naresh R
authors: NR
authors: Thumati
authors: Helen B
authors: HB
authors: Fleisig
authors: Kyle R
authors: KR
authors: Hukezalie
authors: Sharon A
authors: SA
authors: Savage
authors: Neelam
authors: N
authors: Giri
authors: Blanche P
authors: BP
authors: Alter
authors: Judy M Y
authors: JM
authors: Wong
mesh_terms: D055162:Biocatalysis; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D019871:Dyskeratosis Congenita / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression; D005838:Genotype; D020035:Holoenzymes / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D059372:Nucleotide Motifs; D012313:RNA / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability; D019098:Telomerase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D059505:Telomere Homeostasis
chemical_list: D018797:Cell Cycle Proteins; C112148:DKC1 protein, human; D020035:Holoenzymes; D050505:Mutant Proteins; D009687:Nuclear Proteins; C422952:telomerase RNA; D012313:RNA; D019098:Telomerase