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First published online June 4, 2008

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Orc1 takes on telomeres

Genes that are positioned close to the ends of chromosomes, near to telomeric repeats, are often silenced – a process that, in yeast, involves the histone deacetylase Sir2. In the malaria parasite Plasmodium falciparum, Sir2 mediates the silencing of the subtelomeric var genes, which encode key virulence factors and are expressed in a mutually exclusive manner. It has previously been shown that Sir2 silences some, but not all, of the var genes, which indicated that other proteins are involved in their regulation; here, Artur Scherf, Rosaura Hernandez-Rivas and colleagues (p. 2046) identify an additional P. falciparum telomeric protein, Orc1. The authors show that Orc1 localises both to telomeric foci at the nuclear periphery and to the nucleolus – a pattern that is similar to Sir2 localisation. In addition, both proteins bind specifically to the telomere and to subtelomeric repeats, although the pattern of binding is not identical. Strikingly, both Sir2 and Orc1 relocate before DNA replication begins during the P. falciparum blood-stage cycle, and exhibit a more diffuse nuclear and cytoplasmic localisation – this is accompanied by a partial breakdown of telomeric clustering. Orc1 might, the authors suggest, have a similar role to Sir2 in the silencing of subtelomeric genes in P. falciparum.

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Related articles in JCS:

Differential association of Orc1 and Sir2 proteins to telomeric domains in Plasmodium falciparum

Liliana Mancio-Silva, Ana Paola Rojas-Meza, Miguel Vargas, Artur Scherf, and Rosaura Hernandez-Rivas
JCS 2008 121: 2046-2053. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content Social Bookmarking                         What's this?