Protein 10 Stabilizes DNA Replication Enzyme

Researchers working with a yeast model have found that mini-chromosome maintenance protein 10 (Mcm10) plays several roles during cell division including the key role of preventing degradation of DNA polymerase alpha, the enzyme complex that synthesizes new DNA strands.

Investigators at the University of Minnesota (Minneapolis, USA; www.umn.edu) used a yeast model to study the highly conserved proteins involved in DNA and cell replication. They found that one protein in particular, Mcm10, performs several different and critical functions. Some Mcm10 binds to DNA at the site of cleavage and "guides” the DNA polymerase alpha enzyme complex to the correct binding site. Mcm10 also protects DNA polymerase alpha from degradation ensuring that the cellular concentration of this enzyme is maintained. In one mutant yeast strain Mcm10 is lacking, which results in depletion of DNA polymerase alpha and disruption of cell division. Other proteins at the site of replication are not affected. These findings were published in the October 22, 2004, edition of Molecular Cell.

"The big question was, how is polymerase alpha recruited to the first site?” said senior author Dr. Anja 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 stabilizes the polymerase alpha complex. In cells lacking Mcm10, the catalytic subunit of the complex--the part that attaches to DNA--was degraded so it could not attach.”




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