Protein abundant in cancerous cells causes DNA 'supercoiling'

A team of University of Southern Californai (USC) scientists has identified a protein that can change DNA topology, making DNA twist into a so-called ''supercoil.'' The finding provides new insight about the role of the protein - known as mini-chromosome maintenance (MCM) - in cancer cells, which have high levels of MCM.

Think about twisting one end of a rubber band while holding the other end still. After a few turns, it forms a neatly twisted rope. But if you continue turning, the twisted band will eventually twist back upon itself into an increasingly coiled-up knot.

Similarly, a DNA molecule can be twisted and coiled to varying extents to form different supercoiled structures.

Chromosomal DNA forms different supercoiled structures to enable a number of important processes.

It turns on or off some genes, while tuning up or down other genes. The study suggests that an overabundance of MCM in a cell may allow certain genes to be overexpressed and tune down or turn off other important genes, causing the cell to grow out of control and become cancerous.

Chromosomal DNA structure is very important for regulating gene expression of a cell, and thus the physiological status of the cell. Changing DNA topology is one effective way of controlling chromosomal DNA structure.