[ RadSafe ] RESEARCHERS TEST NEW LAB METHOD TO DETECT DNA DAMAGE THROUGHOUT THE GENOME

[John Jacobus]

And science marches forward. 

  -----Original Message-----
From: NIH OLIB (NIH/OD) 
Sent: Tuesday, December 11, 2007 7:55 AM
To: List NIHPRESS
Subject: RESEARCHERS TEST NEW LAB METHOD TO DETECT DNA DAMAGE THROUGHOUT
THE GENOME

U.S. Department of Health and Human Services NATIONAL INSTITUTES OF
HEALTH NIH News National Cancer Institute (NCI)
Embargoed for Release: Monday, December 10,
2007, 8:00 p.m. EST 

Contact: NCI Office of Media Relations 301-496-6641, ncipressofficers at mail.nih.gov>

RESEARCHERS TEST NEW LAB METHOD TO DETECT DNA DAMAGE THROUGHOUT THE
GENOME

In laboratory experiments using budding yeast, the same type used in
baking and brewing, scientists at the National Cancer Institute (NCI),
part of the National Institutes of Health, developed a new approach to
determine the location of unrepaired breaks in DNA. This new approach
should better inform research as unrepaired DNA damage often underlies
the development of cancer. The research findings appear in the December,
2007, issue of "PloS Biology".

The investigators, from NCI's Center for Cancer Research (CCR), examined
meiosis, a form of cell division that produces sperm and eggs in
animals.

During meiosis, a process called recombination may occur that involves
the swapping of genetic material between chromosomes. Chromosomes are
molecules of DNA that carry genes and function in the transmission of
genetic information. For recombination to occur, chromosomal DNA must
first be broken and then spliced together in new combinations, which
creates genetic diversity as new combinations of genes are passed from
parent to child.

"Our new method to detect where DNA is purposefully broken during
meiosis should be a useful tool in understanding the events that start
cells on the road to cancer," said study author Michael Lichten, Ph.D.,
of NCI's Laboratory of Biochemistry and Molecular Biology.

Recent research has shown that recombination is initiated during meiosis
when a protein called Spo11 breaks both strands of the DNA molecule
present in a chromosome. These double-strand breaks (DSBs) are then
efficiently repaired by recombination. While these DSBs are useful
during meiosis, DSBs formed by accident or by chemical damage can be
harmful because they are often incorrectly repaired, creating the kind
of genetic rearrangements that can cause cancer and other diseases. By
studying how yeast efficiently repair the DSBs that occur during
meiosis, researchers aim to develop ways of reducing the impact of
cancer-causing, unrepaired or improperly repaired DNA damage.

When a DSB is caused by the Spo11 protein, the protein sometimes remains
attached to the end of the DSB. Previous methods of detecting DSBs
involved seeking the Spo11 protein to see what DNA was attached. These
methods are not sensitive, and do not detect all of the DSBs that are
formed during meiosis.

Instead of searching for the Spo11 protein, the researchers examined the
single strands of DNA that accumulate at DSBs in mutants that lack
critical recombination proteins. By purifying this single-stranded DNA,
they were able to map yeast DSBs during meiosis at the whole-genome
level. Because this approach finds breaks using a feature common to all
DSBs, it can be used in circumstances where Spo11 is not involved, such
as DSBs that are caused by chemical agents.

Using this new detection approach, the authors took a whole-genome
snapshot of DSB locations. While the previous, less sensitive studies
had suggested that DSBs did not occur in up to 40 percent of the genome
during meiosis, this more sensitive method showed that DSBs were
occurring at similar levels throughout the yeast genome.

The researchers concluded that recombination in yeast is distributed
much more uniformly than previously believed. They predict that their
new mapping method will be useful for studying recombination and DNA
damage in other organisms.

For more information on Lichten's laboratory, please go to
.

For a basic tutorial on Cancer Genomics, please visit

.

For more information about cancer, please visit the NCI Web site at
, or call NCI's Cancer Information Service at
1-800-4-CANCER (1-800-422-6237). 

The National Institutes of Health (NIH) -- The Nation's Medical Research
Agency -- is comprised of 27 Institutes and Centers and is a component
of the U. S. Department of Health and Human Services. It is the primary
Federal agency for conducting and supporting basic, clinical, and
translational medical research, and investigates the causes, treatments,
and cures for both common and rare diseases. For more information about
NIH and its programs, visit .
-----------------------
REFERENCE:
Buhler C, Borde V, Lichten M. Mapping meiotic single-strand DNA reveals
a new landscape of DNA double-strand breaks in "Saccharomyces
cerevisiae". "PloS Biology" December 2007. Vol. 5, No. 12: e324.




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"Courage is what it takes to stand up and speak, Courage is also what it takes to sit down and listen." -- Sir Winston Churchill

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com
       
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