In 2001, scientists announced that they had sequenced the entire human genome, and one of the surprises from this achievement was the discovery that our DNA contains only about 30,000 genes. That number is constantly being revised, but the truth remains that relatively few genes can generate a huge number of proteins. In this Science Update, you’ll hear about a group that’s working to unravel this mystery.
Defeating cancer with its proteins. I'm Bob Hirshon and this is Science Update.
Our genes contain the blueprints for proteins-- the building blocks of life. Now that the entire human genome has been sequenced, geneticists would like to move on to the proteome: a collection of all the proteins coded in our genes. Jon Minden, a biochemist at the Center for Light Microscope Imaging and Biotechnology, says it’s an enormous task.
“In the human body, there’s about five thousand different proteins expressed in every cell. Where there are more than two hundred different cell types and more than ten to the fourteenth cells in the entire body.”
He says teasing out which genes make which proteins and what these proteins do can provide valuable insights into disease. For instance, his lab is gaining a better understanding of cancer by studying proteins using special dyes.
“When a cell becomes cancerous, only a small number of the total five thousand proteins actually change. And we’ve developed techniques that are based on fluorescence to identify which proteins have changed.”
He says researchers can develop new therapies to kill cancer by targeting just those proteins, rather than the entire tumor. For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
Although sequencing the human genome was a huge task, trying to figure out the proteome is more complicated by far. That’s because our genes give the instructions for building all kinds of proteins: the stuff we’re made out of. One person’s body may easily contain over a million different kinds of proteins. And the number of possible things that might happen to these proteins, either through normal growth and development, or because of other factors like drugs and disease, is impossible even to estimate.
But the potential payoff for understanding the body’s proteins is very high. Many diseases, including cancer, hinge on destructive changes in the body’s proteins. If scientists can figure out how to stop those changes, they might be able to stop the diseases.
To better understand the protein changes that take place in cancer, Minden’s team at the research center, which is based at Carnegie Mellon University, has developed a technique using fluorescent dyes. They can “tag” the proteins from normal cells and cancer cells with different colors: for example, a red dye for normal cell proteins, and a green dye for cancer cell proteins.
If they mix normal cells and cancer cells together with the dyes, and then separate out the proteins, they can see which proteins are found in both normal cells and cancer cells (they’ll be tagged with both colors) and which ones are unique to cancer cells (they’ll be just green).
That’s important to know, because if you’re developing chemotherapy drugs to destroy cancerous tumors, you’ll want it to kill off just the cancer proteins without harming the healthy cells. Since many cancer drugs kill healthy tissue along with the cancer, research like this may someday make chemotherapy treatments safer and more effective.
Now try and answer these questions:
- What is the proteome? Why is it so hard to sequence?
- What are some things that can cause changes in the body’s proteins?
- How can understanding the protein composition of the body help doctors treat diseases like cancer?
- Can you think of other diseases in which the cure or treatment can also be harmful? What are some ways to minimize these effects?
Learn about the Human Genome Project at the website for The National Human Genome Project.
Check out Understanding Genetics: Human Health and the Genome, an online exhibit by the Tech Museum.