Nucleolin maintains embryonic stem cell self-renewal by suppression of p53 protein-dependent pathway.
Embryonic stem cells (ESCs) can undergo unlimited self-renewal and retain pluripotent developmental potential. The unique characteristics of ESCs, including a distinct transcriptional network, a poised epigenetic state, and a specific cell cycle profile, distinguish them from somatic cells. However, the molecular mechanisms underlying these special properties of ESCs are not fully understood. Here, we report that nucleolin, a nucleolar protein highly expressed in undifferentiated ESCs, plays an essential role for the maintenance of ESC self-renewal. When nucleolin is knocked down by specific short hairpin RNA (shRNA), ESCs display dramatically reduced cell proliferation rate, increased cell apoptosis, and G(1) phase accumulation. Down-regulation of nucleolin also leads to evident ESC differentiation as well as decreased self-renewal ability. Interestingly, expression of pluripotency markers (Oct4 and Nanog) is unaltered in these differentiated cells. Mechanistically, depletion of nucleolin up-regulates the p53 protein level and activates the p53-dependent pathway, at least in part, via increasing p53 protein stability. Silencing of p53 rescues G(1) phase accumulation and apoptosis caused by nucleolin deficiency entirely, although it partially blocks abnormal differentiation in nucleolin-depleted ESCs. It is noteworthy that knocking down nucleolin in NIH3T3 cells affected cell survival and proliferation in a much milder way, despite the comparable silencing efficiency obtained in ESCs and NIH3T3 cells. Collectively, our data demonstrate that nucleolin is a critical regulator of ESC self-renewal and that suppression of the p53-dependent pathway is the major molecular mechanism underlying functions of nucleolin in ESCs.
Shanghai Stem Cell Institute, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
Acong
A
Yang
Guilai
G
Shi
Chenlin
C
Zhou
Rui
R
Lu
Hui
H
Li
Lei
L
Sun
Ying
Y
Jin
D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation; D058732:Embryoid Bodies / Q000166:cytology / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D020411:Oligonucleotide Array Sequence Analysis; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D000097796:Nucleolin
D010750:Phosphoproteins; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D000097796:Nucleolin