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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.

In This Issue... March 15, 2012

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C. elegans embryo. Image courtesy of Chris Higgins and Liang Gao.

Cool Image: Clutch for Embryonic Development

Bob Goldstein • University of North Carolina at Chapel Hill

C. elegans can grow from a single fertilized egg to a fully developed and functioning organism in just 14 hours. Here, two cells (in blue) migrate from an embryo's surface to its interior, where the cells will form internal structures. Scientists used to think this migration started when a protein motor called myosin pinched the surface and made it shrink. New research in the roundworms suggests that cells, like cars, use a clutch to trigger the pinching of the surfaces. Since C. elegans share many genetic and developmental features with other organisms, including humans, this new knowledge could enhance our understanding of how cells change their shape during critical processes. Image courtesy of Chris Higgins and Liang Gao. Read more... Link to external Website
Stressful conditions contribute to the gain or loss of chromosomes. Credit: Xiang Yuan, Hunan University; Guangbo Chen, Stowers Institute for Medical Research.

Stress Induces Chromosome Changes, Aiding Evolution

Rong Li • Stowers Institute for Medical Research

Cells use intricate control mechanisms to maintain genomic stability, but new research suggests that these mechanisms may relax under certain conditions to enable rapid evolution. In earlier work, researchers found that cells with an abnormal number of chromosomes (aneuploidy) were able to adapt to diverse environmental stresses. By exposing yeast to different chemicals—creating inhospitable conditions—they've now shown that stress can induce genomic instability through the loss or gain of whole chromosomes. The work could have implications for preventing the emergence of drug resistance and for treating cancers involving aneuploid cells. Read more... Link to external Website

Caption: The gain or loss of chromosomes when yeast cells were exposed to stressful conditions is represented as red or green bars, respectively. Credit: Xiang Yuan, Hunan University; Guangbo Chen, Stowers Institute for Medical Research. High res. image (JPG, 52KB)
Synthetic molecule worms into DNA. Credit: Brent Iverson.

New, DNA-Intertwining Molecule Could Target Disease Genes, HIV

Brent Iverson • University of Texas at Austin

In our bodies, many molecules routinely clamp onto DNA, do their business and drop off moments later. Now, scientists have created a molecule that intertwines with a targeted section of DNA and clings to it for up to 16 days. This sort of molecule could bring us closer to the long-sought goal of creating drugs that inactivate specific DNA sequences. Various challenges remain, like getting the molecule into cells and ensuring it attaches only where it's supposed to. But if these can be overcome, the work holds promise for treating genetic diseases, cancer or retroviruses like HIV. Read more... Link to external Website

Caption: This synthetic molecule worms into DNA and stays there for 2 weeks, bringing scientists closer to developing a long-term, DNA-targeting drug. Credit: Brent Iverson. High res. image (JPG, 62KB)
Bacterial daggers. Credit: Everett Kain, California Institute of Technology.

Bacterial 'Daggers' in Action

Grant Jensen • California Institute of Technology

Bacteria have evolved a number of mechanisms to secrete material into the environment and sometimes into neighboring cells. Using a combination of electron cryotomography and fluorescence light microscopy, scientists have now discovered how the common type VI bacterial secretion system works: Tiny tubular structures assemble and then rapidly contract, projecting their contents through their membranes and into the environment. In some cases the contents are dagger-like rods, which puncture neighboring cells and deliver toxins. The research finding may help scientists improve the effectiveness of some antibiotics.

Caption: Bacterial daggers infiltrate others cells and their surrounding environment. Credit: Everett Kain, California Institute of Technology. High res. image (JPG, 40KB)
Structure of stress-specific protein. Credit: Ursula Jakob.

Hsp33: Extending a Helping Hand in Times of Trouble

Ursula Jakob • University of Michigan

Molecular chaperones are proteins that help other proteins fold—either during their construction or when they unravel under unfavorable conditions. A new structural study shows how one of these stress-specific protein helpers works. Molecular chaperone Hsp33 assists bacteria encountering oxidative stress, which can kill cells by causing proteins to unfold and clump together. In response to this stress, Hsp33 partially unfolds: It unreels an arm that it wraps protectively around its unfolded neighbors, averting their potentially deadly aggregation. When the situation is over, Hsp33 retracts its arm and promotes the return of the cell's proteins to their normal shapes and activities.
Read more... Link to external Website

Caption: Three-dimensional structure of the stress-response protein, Hsp33. Credit: Ursula Jakob. High res. image (JPG, 60KB)

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This page last reviewed on March 15, 2011