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Erasing the marks of age
Making old DNA young
By Bijal P. Trivedi

Cloning experiments in the past three years have revealed that transplanting DNA from a differentiated or adult cell—be it an insulin producing pancreatic cell, brain or muscle cell—into an unfertilized egg makes the cell totipotent again. In other words, it is now able to direct the development of any cell in the body.

Exactly how the DNA is "remodeled" or revitalized in an unfertilized egg has remained a mystery until now. Researchers from the National Institutes of Health, in Bethesda, MD and at Sangamo BioSciences in Richmond, CA, have identified a protein that may play a major role in making DNA young.

The researchers found that DNA from differentiated cells is bound to high quantities of the TATA binding protein (TBP). When the differentiated DNA is mixed with the soup of chemicals from an unfertilized egg, more than 90 percent of TBP is removed. The team proposes that TBP may be an important regulator of gene activity and its release may free the DNA of past obligations. Their report, which is published in the September 29 issue of Science, suggests that a protein called ISWI may catalyze the release of TBP from the DNA.

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Kikyo, N. et al. Active remodeling of somatic nuclei in egg cytoplasm by the nucleosomal ATPase ISWI. Science 289, 2360-2362 (September 29, 2000).

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