Biomedical Beat - A monthly digest of research news from NIGMS

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 News.

Cool Image: Microtubule Breakdown

Courtesy of Eva Nogales, a structural biologist at the University of California, Berkeley.
High res. image (173 KB JPEG)

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.

Microtubule Animations
Nogales lab home page

How Household Chemicals Cause Cancer

Mothballs, the structures of cancer-causing chemicals, and a C. elegans with various cells labeled in fluorescent green. Courtesy of Xue.
High res. image (4.43 MB JPEG)
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.

Full story
Xue lab home page
Article abstract (from the June 2006 issue of Nature Chemical Biology)

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 disease.

Full story
Article abstract (from the June 2006 issue of Nature Medicine)

Structure Leads to New Clues for Treating Deadly Infection

Structure of the Hcp1 protein. Courtesy of Cuff.

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Caption: 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.

Full story
Argonne’s Midwest Center for Structural Genomics home page
Protein Structure Initiative home page
Article 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.

Full story
Block lab home page
Landick lab home page (no longer available)
Article abstract (from the June 16, 2006, issue of Cell)