How Gene Transcription Is Controlled In Embroyonic Stem Cells
ScienceDaily (May 6, 2008) — Association determines fate in embryonic
stem cells, said Baylor College of Medicine researchers in a report
that appears in the current issue of the journal Nature Cell Biology.
"These findings provide models of how the embryonic stem cell is
maintained in its flexible state," said Dr. Zhou Songyang, professor
of biochemistry and molecular biology at BCM and senior author of the
report. "It provides another hint as to how gene transcription is
controlled in embryonic stem cells."
One aim of embryonic stem cell research is to understand how the
cells determine whether they will keep dividing and maintain a pool
of embryonic cells, or start the process of cellular differentiation
that results in different cell types.
Songyang and his colleagues found that two critical embryonic cell
proteins -- Nanog and Oct4 -- associate with specific components that
are parts of transcription repression complexes. These complexes
affect the way that genes are expressed and carry out their tasks in
the cell.
A special complex called NODE (Nanog and Oct4-associated Deacetylase)
contains a critical component called Mta1 along with histone
deacetylases. NODE associates with Nanog and Oct4 to control the fate
of embryonic stem cells, said Songyang.
Histones are critical parts of genomic DNA structures or chromatins,
acting as "spools" around which the genetic material winds in the
nucleus. The DNA wraps more tightly when deacetylase removes the
acetyl tails from the histones. The tight wrapping makes it hard for
genes to be transcribed into the message that allows them to carry
out their roles in the cell.
"Think of it as the parts of a car," said Songyang. "If you think of
Nanog as the engine that drives it, you realize that the car still
needs accessories like wheels, the tailpipe, etc. We are interested
in the big machinery of which proteins (like Nanog) are the drivers.
We want to understand the enzymatic activities of the complexes. Then
we need to identify the individual parts and ask the big
question: 'How do different parts work together and why do you need
special parts"'"
"We noticed that there are many histone deacetylases,
said. "Nanog uses these proteins to control gene expression and maybe
also the chromatin state. When there is deacetylation, the gene is in
a passive state."
"The embryonic stem cell is always at the stage of deciding whether
to divide (and make more embryonic stem cells) or to differentiate,
Songyang said. "All the extrinsic and intrinsic signals make the life
of the embryonic stem cell transient. In other words, it has to be
ready to go down either road."
"It becomes an interesting question," said Songyang. "Such a
demanding state of readiness may mean that the embryonic stem cell
requires a different complex at the chromatin than the somatic (or
differentiated cell)."
Others who took part in the research include Jiancong Liang, Ma Wan,
Yi Zhang, Peili Gu (now of The University of Texas M.D. Anderson
Cancer Center), Huawei Xin, Sung Yun Jung, Jun Qin, Jiemin Wong,
Austin J. Cooney and Dan Liu, all of BCM. Funding for this work comes
from the National Institutes of Health, the Leukemia and Lymphoma
Society and the American Heart Association.
Adapted from materials provided by Baylor College of Medicine.
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MLA Baylor College of Medicine (2008, May 6). How Gene Transcription
Is Controlled In Embroyonic Stem Cells. ScienceDaily. Retrieved May
6, 2008, from http://www.scienced
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http://www.CNSfoundation.org/
Cord Blood Registry
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The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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