To convert a piece of cloned DNA into a centromere-containing human artificial chromosome (HAC), an array of repeated LacO sequences is incorporated into the DNA. The DNA is then transfected into human cells that have been engineered to express a fusion protein consisting of a LacO binding domain and a factor called HJURP. The fusion protein binds to the LacO domains (1), and incorporates the specialized centromeric histone CENP-A into and along neighboring chromatin (2). In turn, the region of CENP-A-containing chromatin forms a centromere, converting the cloned DNA into a functional self-perpetuating HAC (3).
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Ruth Williams is a freelance journalist based in Connecticut. Email her at firstname.lastname@example.org or find her on Twitter @rooph.