Sister chromatid cohesion establishment during DNA replication termination. (https://pubmed.ncbi.nlm.nih.gov/38484038/)

These scientists wanted to understand how cells make sure that when they copy their DNA, the new copies stay together until they are ready to be split apart. They looked at a part of the cell called the cohesin complex that helps keep the newly copied DNA strands, called sister chromatids, connected.

The scientists thought that the cohesin complex stays in place on the DNA before it gets copied, and then moves along with the copying process to keep the new copies together. But when they looked closely at what happens when the copying process meets the cohesin complex, they found something surprising.

Instead of the cohesin complex moving with the copying process, the copying machinery actually pushes the cohesin complex towards another copying process coming from the opposite direction. This helps the cohesin complex stay in place and keep the new DNA copies together.

After both copying processes are done, the cohesin complex remains on the new DNA and helps keep the copies connected until they are ready to be separated. The scientists also found that when the copying machinery is taken apart at the end of the process, it is important for the cohesin complex to stay in place properly.

Overall, the scientists discovered a new way in which cells make sure that the new DNA copies stay connected until they are fully copied and ready to be used.

Cameron G., Gruszka DT., Gruar R., Xie S., Kaya C., Nasmyth KA., Baxter J., Srinivasan M., Yardimci H. Sister chromatid cohesion establishment during DNA replication termination. Science. 2024 Mar 14:eadf0224. doi: 10.1126/science.adf0224.