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Copying DNA is no moveable feast

发布时间:2019-03-08 06:05:08来源:未知点击:

By Jonathan Knight GENETIC material is churned out in DNA factories anchored to cell membranes rather than by roving enzymes as previously supposed. Before a cell divides, it replicates all its DNA so each daughter cell will inherit a copy of its genes. DNA polymerase, the complex of enzymes that copies DNA, was thought to travel along the double helix like a train on tracks. But it was also possible that DNA polymerases stayed in one spot like a fixed DNA factory. “People have seen replication factories,” says Alan Grossman of the Massachusetts Institute of Technology. “But they have never been able to tell whether they move.” To find out, Grossman and Katherine Lemon attached a green fluorescent protein from jellyfish to DNA polymerase in the bacterium Bacillus subtilis. As the bacteria divided, they tracked the position of the polymerase complexes within the cell by their green glow. The polymerases replicated the bacterium’s genes without straying from their spot next to the cell membrane (Science, vol 282, p 1516). Grossman believes fixed DNA factories are probably at work in human cells too. “I think it’s going to be identical,” he says. “No one imagined something like this in bacteria,