July 17, 2006 | David F. Coppedge

Cell Untangles Its Own DNA

DNA is packed like spaghetti in a basketball (07/28/2004), but must constantly be accessed by transcribers, duplicators and other molecular machines.  Scientists at the Karolinska Institute, according to EurekAlert, have found a complex of protein machines that know how to untangle DNA.  Machines that can keep DNA from separating too early (cohesins) and keep DNA coils compact (condensins) have been studied extensively, but these scientists looked more at another mechanism.  When they artificially perturbed DNA strands, the machines went to work fixing the damage:

The research group has studied the third, less well understood, protein complex, known as the Smc5/6 complex.  This protein complex was found to bind to locations on the DNA strand that the researchers had artificially damaged, suggesting that it is directly involved in the repair process.  Moreover, the Smc5/6 complex also seems to be required for the disentanglement of undamaged chromosomes before cell division.  If these tangles, which are a natural consequence of the DNA copying process, are left unresolved the chromosomes cannot be separated and sent to the two nascent daughter cells.  Like in the repair process, the Smc5/6 complex appears to resolve these intertwines by direct interaction with the DNA molecules, but this process is differently regulated as compared to the function in repair.

The press release starts with a “wow” factoid: “Every second, the cells constituting our bodies are replaced through cell division.  An adult human consists of about 50,000 billion cells, 1% of which die and are replaced by cell division every day.”  Machines like the Smc5/6 complex are essential to maintaining our genomic integrity.

So, evolutionists, tell us again about how this all worked out in the mythical RNA world when none of these repair and maintenance mechanisms had yet accidentally emerged.

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