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ArticleJournal InfoAuthorsReviewers Mol Cell Biol. Dec 2006;
26(24): 9279–9290. Published online Sep 25, 2006. doi: 
10.1128/MCB.00724-06 PMCID: PMC1698521  Nucleostemin Delays
Cellular Senescence and Negatively Regulates TRF1 Protein
Stability[down-pointing small open triangle]   Nucleostemin (NS)
encodes a nucleolar GTP-binding protein highly enriched in the
stem cells and cancer cells. To determine its biological
activity in vivo, we generated NS loss- and gain-of-function
mouse models. The embryogenesis of homozygous NS-null (NS−/−)
mice was aborted before the blastula stage. Although the growth
and fertility of heterozygous NS-null (NS+/−) mice appeared
normal, NS+/− mouse embryonic fibroblasts (MEFs) had fewer NS
proteins, a lower population growth rate, and higher percentages
of senescent cells from passage 5 (P5) to P7 than their wild-
type littermates. Conversely, transgenic overexpression of NS
could rescue the NS−/− embryo in a dose-dependent ma