Making new cells - Copying DNA

Copying DNA DNA contains the ‘instruction manual’ for the cell, packaged in the form of genes. Our genes control every aspect of a cell’s activities, including telling it when to multiply, what sort of cell to become, and when to die.

When a cell’s DNA is copied at the beginning of the cell cycle, it is vital that this only happens once – and that it’s copied accurately.

If not, then the ‘daughter’ cells will have the wrong amount of DNA. They may be missing important genes, or have too many copies of them, which can lead to cancer.

Many cancer drugs work by interfering with the DNA copying process – known as DNA replication – in cancer cells. They are effective because cancer cells divide more often that most healthy cells. But the drugs cause side effects such as hair loss and sickness, because they also stop some healthy cells from dividing.

Over the years, our researchers have played an important part in understanding the DNA replication machinery. But we still need to discover more about how DNA is copied normally and why this process is different in cancer cells. This will help us understand more about the disease and identify new targets for kinder, more effective future treatments.

Getting DNA replication started

Understanding the DNA ‘replication machines’ in cells

Professor Ron Laskey in Cambridge, who we’ve funded for two decades, is one of the world’s leading experts in DNA replication. He has identified molecules called MCM proteins, which help to trigger the DNA copying process. Because cancer cells are continuously dividing, they are likely to contain more of these proteins than normal cells.

Researchers are now working on ways to measure levels of MCM proteins in urine or other samples. This is being developed into tests to detect several different types of cancer, including cervical, prostate and bladder cancer. Some of these tests are currently undergoing clinical trials, for example for bladder cancer and bile duct, gallbladder or pancreatic cancer.

Dr John Diffley – Director of the Clare Hall laboratories at our London Research Institute – is internationally renowned for his research on DNA replication. He and his team have studied this process in yeast cells and, over the past 20 years, have made many important discoveries.

In particular, they have shed light on the proteins that kick-start the DNA copying process. These are known as ‘licensing factors’ - they build up in cells during the early stages of the cell cycle and tell them where to start copying the DNA.

At the University of Dundee, Professor Julian Blow is using frog egg cells to investigate how cells ensure each piece of DNA gets copied once and only once. And Dr Karim Labib at the Paterson Institute for Cancer Research in Manchester is working to identify the molecular 'nuts and bolts' of the ‘machinery’ that copies DNA.

At our London Research Institute, Dr Dale Wigley is studying the proteins involved in both copying and repairing DNA. One of these - a 'detangler' called topoisomerase - unwinds the twisted structure of DNA so it can be copied. Certain anti-cancer drugs – like etoposide – work by blocking topoisomerase.