The Two Faces of p53 in Embryonic Stem Cells When damage occurs
such as UV radiation, p53 expression plays a dual role in
embryonic cells. Its expression both removes the unhealthy cells
from the stem-cell pool by promoting programmed cell death or
differentiation. At the same time, p53 activates the Wnt pathway
to inhibit the differentiation of surrounding, healthy embryonic
stem cells to maintain a population for the development of the
organism. Mutations in the genome of a cell can have dire
effects. This type of damage can be even more devastating if it
occurs in stem cells, since any changes will be passed on to all
subsequent generations. Consequently, there are many checkpoints
to alert cellular machinery of changes in the DNA. p53 monitors
cells for damage from many types of environmental stress and is
a type of protein called a transcription factor. Transcription
factors bind to DNA at specific sites and facilitate the
expression of genes. When damage occurs, p53 activates specific
pathways to assess