Rising to new heights
Dr. Jennifer Cobb is cooking up a storm of research using yeast.
Story by Sheelagh Matthews/Photo by Getty Images
A staple from the kitchen cupboard is helping the research of AHFMR Scholar Dr. Jennifer Cobb rise to new heights at the University of Calgary. Baker's yeast is the secret ingredient in her success.
Dr. Cobb investigates DNA repair, DNA replication, and the separation of chromosomes during cell division. She wants to understand how a healthy cell transforms into a cancer cell. "We know it's not good to eat certain foods or get too much sunshine, but why?" she asks. "What is really going on inside the cell? How is the genome affected?"
Upon exposure to genotoxic stress, like too many strong UV rays from the sun, our cells activate biochemical pathways to prevent the genetic material in our cells from becoming damaged and unstable. But what happens when these safety mechanisms fail and mutations arise? Dr. Cobb's team is particularly interested in how these genomic instabilities predispose people to developing cancer. (A genome is all the genetic information in one set of an organism's chromosomes. Genomic rearrangements occur when chromosomes do not replicate completely or when damaged DNA is not repaired accurately.)
According to Dr. Cobb, "We know that most cancers have genomic rearrangements and mutations, but what's less clear is whether this instability is a cause of cancer, a consequence of cancer, or a driving force in cancer progression. It is likely a combination of these."
Named after Ceres, the Roman goddess of agriculture, Saccharomyces cerevisiae (yeast) is used by scientists all around the world. This single-celled organism has had a remarkable impact in scientific research. First of all, the life cycles of S. cerevisiae and mammalian cells are so similar that understanding what goes on in yeast cells can help in understanding human cells. Moreover, some experiments are much easier to perform on yeast cells than on human cells, because S. cerevisiae cells replicate quickly, and their genetic material is easily manipulated.
The accurate transmission of genetic material from one generation of cells to the next is better understood today thanks to the first model of deoxyribonucleic acid, more commonly known as DNA, created by James Watson and Francis Crick in 1953. DNA provides instructions on how to create all the molecules the cell needs to function. Because cells are continuously being created and replaced, they are constantly replicating their genetic information. Imagine the potential for error, when millions of these complex DNA replication processes go on every day within our bodies. Normally, the internal cell factory keeps generating healthy cells, but sometimes these events go awry. If the system that makes sure replication occurs correctly does not function properly, then genetic information can get lost. This is when problems start to show up—once genetic information goes missing, it can't be replaced. Moreover, parts of our genetic code can be lost if cells are damaged; for example, by ultraviolet (UV) rays. But regardless of how the DNA damage occurs, it leads to genomic rearrangements, which are often found in cancer patients.
Recently, Dr. Cobb's efforts have revealed that a group of proteins called the MRX complex helps stabilize DNA during replication. More specifically, the MRX complex helps prevent bits of genetic information from flying off in all directions. If the MRX complex can't function properly, research has shown the consequence to be genomic rearrangements and, in humans, a predisposition to breast cancer. Figuring out how the MRX complex protects the molecular structure of DNA will allow researchers to understand why cancer develops in individuals with MRX complex deficiencies. Dr. Cobb hopes her research on yeast will provide a foundation for developing cancer treatments and cures.