MINNEAPOLIS / ST. PAUL--In order to divide, cells must first replicate their chromosomes. Cells use an array of proteins to accomplish the job, including a large enzyme complex that synthesizes new strands of DNA. In a paper to be published Oct. 22 in the journal Molecular Cell, University of Minnesota researchers report that a particular protein, called minichromosome maintenance protein 10 (Mcm10), protects the enzyme from destruction and, like a molecular tugboat, escorts it to its "port"--the location on a chromosome where DNA replication will begin. Mcm10's versatility implies that it is indispensable for cell division. Therefore, drugs that target Mcm10 could be effective in stopping the uncontrolled cell division seen in cancerous tumors.

The work grew out of a desire to learn the identity of the "tugboat," said Anja Bielinsky, an assistant professor of biochemistry, molecular biology and biophysics, in whose laboratory the work was performed. The first author on the paper is Robin Ricke, a graduate student. The two scientists worked with baker's yeast, an organism often used to study basic biological mechanisms.

First, a little background on how DNA replicates itself: Before DNA replication can begin, the two strands in the DNA double helix must be unwound. Next, multiple molecules of a certain protein attach to the strands to keep them from spontaneously sticking together again. Only then can the star of the show--DNA polymerase alpha, the enzyme complex that synthesizes new DNA strands--be escorted to the specific sites on the DNA strands where it can attach and go to work.

"The big question was, How is polymerase alpha recruited to the first site?" said Bielinsky. "We found that Mcm10 brings the DNA polymerase alpha complex to the chromosomal sites where replication originates. It does this by attaching to the protein that keeps the two DNA strands from reconnecting. But what came as a complete surprise was that Mcm10 also stabiliz
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Contact: Deane Morrison
morri029@umn.edu
612-624-2346
University of Minnesota
21-Oct-2004

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