Telomeres are replicated by the enzyme telomerase, a ribonucleoprotein that adds telomeric repeats to the 3′ ends of chromosomes. The biochemistry of this reaction has been established, but how the end-replication machinery is organized in vivo and what the roles of telomerase-associated proteins such as p43 are remain obscure. Hans Lipps and co-workers have therefore investigated this in Euplote, a spirotrichous ciliate whose macronucleus has numerous telomeres (see p. 1757). They demonstrate that telomerase and p43 form complexes that are anchored to the nuclear matrix by p43. Electroelution experiments indicate that the telomerase and p43 remain associated with the nuclear matrix whereas the telomeric sequences themselves are released during replication. Using RNAi for the first time in a spirotrich, the authors go on to demonstrate that removal of p43 or telomerase not only prevents the proteins from associating with the nuclear matrix but also produces nuclear defects likely to be caused by defective DNA replication. They suggest that binding of telomerase induces a structural change in p43 that allows it to anchor the p43-telomerase complex on the nuclear matrix, where the enzymatic complex must reside to function efficiently.
- © The Company of Biologists Limited 2003