IN THIS ISSUE . . .
July 18, 2006
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The National Institute of General Medical Sciences (NIGMS),
one of the National Institutes of Health, supports all research
featured in this digest. Although only the lead scientists
are named, coworkers and other collaborators also contributed
to the findings. To read additional news items, visit NIGMS
Cool Image: Microtubule Breakdown
Like a building supported by a steel frame, a cell contains
its own sturdy internal scaffolding made up of proteins, including
microtubules. Researchers studying snapshots of microtubules
have proposed a model for how these structural elements shorten
and lengthen, allowing a cell to move, divide, or change shape.
This picture shows an intermediate step in the scientist's
model: Smaller building blocks called tubulins peel back from
the microtubule in thin strips. Knowing the operations of
the internal scaffolding will enhance our basic understanding
of cellular processes. Courtesy of Eva Nogales, a structural
biologist at the University of California, Berkeley.
lab home page
How Household Chemicals Cause Cancer
Caption: Mothballs, the
structures of cancer-causing chemicals, and a C.
elegans with various cells labeled in fluorescent
green. Courtesy of Xue.
Scientists have shown how the household chemicals in mothballs
and air fresheners might cause cancer. Cell biologist Ding
Xue of the University of Colorado at Boulder found that the
chemicals naphthalene and para-dichlorobenzene can interfere
with the process of programmed cell death, or apoptosis. When
Xue exposed Caenorhabditis elegans (a roundworm widely
used as a model organism for lab studies) to the chemicals,
he found that the worms contained extra cells. This indicated
that the chemicals promoted cell survival and proliferation—a
hallmark of cancer. Taking a closer look, Xue determined that
the chemicals block enzymes called caspases that are essential
to programmed cell death. This work shows that C. elegans
could be used to identify other potential cancer-causing agents
and to screen for new drugs.
lab home page
abstract (from the June 2006 issue of Nature Chemical
Mouse Model Uncovers COX Partnership
A new study suggests that the roles of COX-1 and COX-2 enzymes—targets
of many pain medications—may be more complex than scientists
previously thought. The study, led by biochemist and physiologist
Colin Funk of Queen’s University in Kingston, Ontario,
Canada, examined the way in which these two enzymes work together
in mice whose COX-2 enzymes were constantly inhibited, as
they might be for someone regularly taking a drug like Vioxx
or Celebrex. Earlier work showed that newborn mice completely
lacking the COX-2 enzyme developed a specific defect in their
cardiovascular systems. The latest results suggest that COX-1
can rescue the activity of an inhibited COX-2 and allow an
important artery to properly mature after a mouse is born.
The work also suggests that researchers need to continue exploring
the different roles the COX enzymes play in physiology and
abstract (from the June 2006 issue of Nature Medicine)
Structure Leads to New Clues for Treating
Structure of the Hcp1 protein. Courtesy of Cuff.
Crystallographers routinely capture structural information
about proteins and then deposit that information into a
public database. When Marianne Cuff of Argonne National
Laboratory did this for a protein called Hcp1, she sparked
a collaboration with scientists 1,000 miles away. Researchers
at Harvard Medical School had been studying a similar protein
secreted by the bacterium that causes cholera. When they
came across Cuff’s Hcp1 in the database, they thought
that it might get secreted by the bacterium that produces
it--Pseudomonas aeruginosa, a leading cause of
deadly infections among people with cystic fibrosis. The
two teams worked together to confirm this hypothesis. The
finding offers a possible drug target for treating this
infection. The study, supported by the NIGMS Protein Structure
Initiative, points to the value of developing a representative
collection of proteins from which other structures and functions
can be determined.
This work was co-funded by the National Institute of Allergy
and Infectious Diseases at NIH.
Midwest Center for Structural Genomics home page
Structure Initiative home page
abstract (from the June 9, 2006, issue of Science)
Pinpointing Polymerase Pauses
In the cellular assembly line, RNA polymerase slides along
DNA, transcribing a gene into RNA used to make proteins. How
fast and how often the RNA polymerase enzyme transcribes a
gene is one way that the cell controls gene expression. While
scientists knew that the enzyme pauses occasionally as it
transcribes, they weren’t sure why. Steven Block and
Robert Landick—a Stanford University biophysicist and
a University of Wisconsin-Madison molecular biologist, respectively—measured
the speed of the enzyme along a strand of DNA and found that
RNA polymerase pauses at specific DNA sequence sites. Understanding
why and how these pauses occur may give scientists new insight
into ways cells control the expression of their genes.
lab home page
lab home page
abstract (from the June 16, 2006, issue of Cell)