Lina Zeldovich in Nautilus:
Deep inside the tens of trillions of cells that comprise your body, the DNA replication machinery is constantly speeding along in many tissues. In the bone marrow alone, 500 million red and white blood cells are produced every minute. There’s about two meters of DNA in each cell, neatly woven inside the nucleus. To keep the blood cell supply steady, about a billion meters of DNA must be copied every minute. “You could wrap that around the Earth along the equator about 25 times,” Stillman says. It is inevitable that over the course of a person’s lifetime, this process will make mistakes—some harmless, but others leading to malignant mutations. So, understanding the cogs of this complex machinery may hold the key to combating many cancers.
Stillman and his team discovered that the replication process starts with a set of six specific proteins called Origin Recognition Complex, or ORC. The proteins bind to the DNA at specific locations and recruit more proteins to help, forming what’s called the pre-replicative complex. This pre-replicative complex “gives permission” to start DNA replication and many proteins begin copying the genetic material from their respective starting points. Once the job is finished, the pre-replicative complex is destroyed. Once the cell is ready to divide again, the complex is formed anew.