Yeast, genes, and green-glowing machines

In case you didn’t know, there is a lab making glowing green baker’s yeast at K-State. Are these mad scientists trying to create neon green baked goods that will be a smash hit at parties? While some people may be sad to hear that’s not the case, these glowing green yeast are actually being used to investigate questions that might lead to treatments for cancer and other diseases.

Even though yeast look very different from humans, many researchers use these single celled fungi for human health studies because their cellular machinery is so similar to ours. Just as importantly, yeast are able to reproduce rapidly, are easy to keep in a laboratory, and researchers can manipulate many aspects of their basic biology, like making them glow green! Scientists have figured out how to take a gene from jellyfish and stitch it onto any yeast protein that they are interested in studying, turning the cells green, red , blue and many colors in between. This allows researchers to track the production of specific proteins. So, every time the yeast cell makes the protein of interest, a colorful jellyfish protein is made as well. This gives scientists a very handy tool! By measuring how bright the yeast cells glow, scientists can figure out how much of the protein of interest is being made and where it goes in the cell.

Akeem Waite, a Ph.D. student in the Division of Biology, uses glowing yeast to study a part of the cell known as the proteasome. Proteasomes are important pieces of molecular machinery found inside the cells of plants, fungi, and animals. These tiny structures can be thought of as cellular woodchippers because, just as a woodchipper takes a log and chops it up into tiny woodchips, the proteasome’s main job is to break down proteins into smaller molecules called amino acids. Proteins are the building blocks that make up all living things and perform all sorts of important tasks, so why would cells break them down? Here’s the issue: having too much of a protein at the wrong time or place can cause serious problems. Cells need a way to get rid of proteins once they have completed their jobs, but why waste when the cell can recycle an old protein’s amino acids to make future proteins? This is where the woodchipper comes in. Once they’re no longer needed, proteins go in to the proteasome, where they get chopped up and the smaller amino acids come out, ready to be used by the cell for other jobs.

KSU graduate student Akeem looking at yeast cells under a microscope

Just like all machines, sometimes these cellular woodchippers can malfunction or become damaged. Having too many broken proteasomes around can lead to the build-up of proteins in the cell, or proteasomes may start mistakenly chopping up proteins that are still needed. Other times, the cell itself can malfunction and produce too many proteasomes, also causing proteins to be broken down before their jobs are done. In fact, some forms of cancer develop when proteasomes interrupt regular cell activity by breaking down proteins that signal when it is time for the cell to stop growing or dividing, allowing tumors to grow. To avoid problems that can cause disease, it’s important that cells have a way to control the number of proteasomes around and to take care of faulty proteasomes. Akeem is investigating how cells manage damaged proteasomes. Other scientists have shown that some damaged proteasomes are “labeled” by the cell with a specific protein, but what this labeling does is still unknown. With this knowledge, Akeem adds a colored protein to the labeled proteasomes, and follows them through the cell to find out what happens; are these faulty proteasomes themselves broken down and their parts recycled by the cell or are they repaired and sent back to chopping?

Image A shows how yeast cells look under a microscope. Akeem can attach different colored proteins to different parts of the  proteasomes in these cells (B and C). This way, he can follow multiple parts of the proteasome at the same time (D).

So far, Akeem has found that the cell does not break down proteasomes labeled by this protein. In fact, these labeled proteasomes are found at high concentrations in the cell’s nucleus, and Akeem is now testing whether the marker protein may play a role in the repair of proteasomes within the nucleus itself. By gaining a better understanding of how cells manage their proteasomes, Akeem’s research is adding to the body of knowledge that can be used to help understand and develop treatments for diseases that involve proteasome functioning.


This post was written by Ryan Greenway. Ryan is a biology Ph.D. student that uses fish to study how ecology and evolution interact to create the diversity of life on our planet.

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