New telomere discovery could help explain why cancer cells never stop
dividing
2007-10-06 00:35.
Lausanne, Switzerland, October 4, 2007 – A group working at the Swiss
Institute for Experimental Cancer Research (ISREC) in collaboration
with the University of Pavia has discovered that telomeres, the
repeated DNA-protein complexes at the end of chromosomes that
progressively shorten every time a cell divides, also contain RNA.
This discovery, published online October 4 in Science Express, calls
into question our understanding of how telomeres function, and may
provide a new avenue of attack for stopping telomere renewal in
cancer cells.
Inside the cell nucleus, all our genetic information is located on
twisted, double stranded molecules of DNA which are packaged into
chromosomes. At the end of these chromosomes are telomeres, zones of
repeated chains of DNA that are often compared to the plastic tips on
shoelaces because they prevent chromosomes from fraying, and thus
genetic information from getting scrambled when cells divide. The
telomere is like a cellular clock, because every time a cell divides,
the telomere shortens. After a cell has grown and divided a few dozen
times, the telomeres turn on an alarm system that prevents further
division. If this clock doesn't function right, cells either end up
with damaged chromosomes or they become "immortal" and continue
dividing endlessly – either way it's bad news and leads to cancer or
disease. Understanding how telomeres function, and how this function
can potentially be manipulated, is thus extremely important.
The DNA in the chromosome acts like a sort of instruction manual for
the cell. Genetic information is transcribed into segments of RNA
that then go out into the cell and carry out a variety of tasks such
as making proteins, catalyzing chemical reactions, or fulfilling
structural roles. It was thought that telomeres were "silent" – that
their DNA was not transcribed into strands of RNA. The researchers
have turned this theory on its head by discovering telomeric RNA and
showing that this RNA is transcribed from DNA on the telomere.
Why is this important" In embryonic cells (and some stem cells), an
enzyme called telomerase rebuilds the telomere so that the cells can
keep dividing. Over time, this telomerase dwindles and eventually the
telomere shortens and the cell becomes inactive. In cancer cells, the
telomerase enzyme keeps rebuilding telomeres long past the cell's
normal lifetime. The cells become "immortal", endlessly dividing,
resulting in a tumor. Researchers estimate that telomere maintenance
activity occurs in about 90% of human cancers. But the mechanism by
which this maintenance takes place is not well understood. The
researchers discovered that the RNA in the telomere is regulated by a
protein in the telomerase enzyme. Their discovery may thus uncover
key elements of telomere function.
"It's too early to give yet a definitive answer," to whether this
could lead to new cancer therapies, notes Joachim Lingner, senior
author on the paper. "But the experiments published in the paper
suggest that telomeric RNA may provide a new target to attack
telomere function in cancer cells to stop their growth."
http://cancerfocus.
ancer_cells_
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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