p53 pathway activation by telomere attrition in X-DC primary fibroblasts occurs in the absence of ribosome biogenesis failure and as a consequence of DNA damage.
BACKGROUND
Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome with high clinical heterogeneity. Various mutations have been reported in DC patients, affecting genes that code for components of H/ACA ribonucleoproteins, proteins of the telomerase complex and components of the shelterin complex.


OBJECTIVE
We aim to clarify the role of ribosome biogenesis failure in senescence induction in X-DC since some studies in animal models have reported a decrease in ribosome biogenesis as a major role in the disease.


METHODS
Dyskerin was depleted in normal human fibroblasts by expressing two DKC1 shRNAs. Common changes in gene expression profile between these dyskerin-depleted cells and X-DC fibroblasts were analyzed.


RESULTS
Dyskerin depletion induced early activation of the p53 pathway probably secondary to ribosome biogenesis failure. However, the p53 pathway in the fibroblasts from X-DC patients was activated only after an equivalent number of passes to AD-DC fibroblasts, in which telomere attrition in each division rendered shorter telomeres than control fibroblasts. Indeed, no induction of DNA damage was observed in dyskerin-depleted fibroblasts in contrast to X-DC or AD-DC fibroblasts suggesting that DNA damage induced by telomere attrition is responsible for p53 activation in X-DC and AD-DC fibroblasts. Moreover, p53 depletion in senescent DC fibroblasts rescued their proliferative capacity and reverted the morphological changes produced after prolonged culture.


CONCLUSIONS
Our data indicate that ribosome biogenesis do not seem to play an important role in dyskeratosis congenita, conversely increasing DNA damage and activation of p53 pathway triggered by telomere shortening is the main activator of cell senescence.
Instituto de Investigaciones Biomédicas de Madrid CSIC/UAM, IDIPaz (Biomarkers and Experimental Therapeutics Group), C/Arturo Duperier, 4, 28029, Madrid, Spain.
J
J
Carrillo
A
A
González
C
C
Manguán-García
L
L
Pintado-Berninches
R
R
Perona
D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D004249:DNA Damage / Q000235:genetics*; D019871:Dyskeratosis Congenita / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012270:Ribosomes / Q000502:physiology*; D016615:Telomere / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
D015415:Biomarkers; D018797:Cell Cycle Proteins; C112148:DKC1 protein, human; D009687:Nuclear Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53