Cold Spring Harbor, New York, December 21, 2023 /PRNewswire/ — When organisms pass their genes on to their offspring, they contain more than just the code spelled out in their DNA. Some also deliver chemical tags that instruct cells how to use the code. These marks are passed on to future generations called epigenetic inheritance. It is particularly common in plants. So a major discovery here could have implications for agriculture, food supplies and the environment.
Cold Spring Harbor Laboratory (CSHL) professor and HHMI researcher Rob Martinson and Limore Joshua Toll has been studying how plants pass on markers that keep transposons inactive. Transposons are also called jumping genes. When turned on, they can move around and damage other genes. To silence them and protect the genome, cells add regulatory tags to specific DNA sites. This process is called methylation.
Martienssen and Joshua-Tor have now shown how the protein DDM1 makes way for enzymes that place these tags on new DNA strands. plant cells DDM1 is required because their DNA is tightly packed. To keep the genome compact and organized, cells wrap the DNA around packaging proteins called histones. “But this prevents various important enzymes from accessing the DNA,” Martienssen explains. Before methylation can occur, “you have to remove or slide away the histones.”
Martienssen and former CSHL colleagues Eric Richards first Discover DDM1 30 years ago. Since then, researchers have learned that it slides DNA along packaging proteins to expose sites that require methylation. Martinson likens the sport to a yo-yo gliding along a rope. Histones “can move up and down the DNA, exposing parts of it at a time but never falling off,” he explains.
Through genetic and biochemical experiments, Martienssen pinpointed the exact histone that DDM1 replaced. Using Joshua-Tor cryo-electron microscopy Capture detailed images of enzyme interactions with DNA and associated packaging proteins. They were able to see how DDM1 grabs onto specific histones to remodel the packaged DNA. “It turns out that an unexpected bond holding DDM1 together corresponds to the first mutation discovered many years ago,” Joshua-Tor said.
The experiments also revealed how DDM1’s affinity for certain histones maintains epigenetic control across generations. The team showed that a histone protein found only in pollen is resistant to DDM1 and acts as a placeholder during pollen growth. Cell division. “It remembers the location of histones during plant development and retains this memory into the next generation,” Martienssen said.
The plants here may not be alone. Humans also rely on DDM1-like proteins to maintain DNA methylation. The new discovery may help explain how these proteins maintain the function and integrity of our genomes.
About Cold Spring Harbor Laboratory
Founded in 1890, Cold Spring Harbor Laboratory has shaped contemporary biomedical research and education through programs in cancer, neuroscience, plant biology, and quantitative biology. The private, not-for-profit laboratory is home to eight Nobel Prize winners and has 1,000 employees, including 600 scientists, students and technicians.For more information, please visit www.cshl.edu
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SOURCE Cold Spring Harbor Laboratory
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