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First published online February 4, 2009

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SIRT7 gets rDNA transcription going

Over half of the RNA synthesis in the cell takes place during transcription of ribosomal DNA (rDNA) – a nucleolar process that is tightly regulated in response to cell-cycle stage, ageing, starvation and other factors. For instance, rDNA transcription is repressed during mitosis, but we lack a complete picture of how this is controlled. Now, Valentina Sirri and colleagues (p. 489) investigate the mitotic activity of SIRT7, a nucleolar histone deacetylase that has been reported to help regulate rDNA transcription. The authors show that, in contrast to previous reports, SIRT7 associates with nucleolar organiser regions (NORs; the chromosomal sites at which rDNA genes cluster) even when rDNA transcription is repressed, and that this localisation is mediated by a direct interaction between SIRT7 and the rDNA transcription factor UBF. They next show that SIRT7 is phosphorylated by the CDK1–cyclin-B pathway during mitosis, then dephosphorylated before rDNA transcription resumes after mitosis. Moreover, the resumption of transcription requires SIRT7 activity, and the SIRT7 C-terminus becomes more reactive to cognate antibodies before transcription begins. The authors propose, therefore, that dephosphorylation of SIRT7 promotes a change in its conformation, and that this derepresses transcription. Their data underscore the complexity of rDNA transcriptional regulation.

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Involvement of SIRT7 in resumption of rDNA transcription at the exit from mitosis

Alice Grob, Pascal Roussel, Jane E. Wright, Brian McStay, Danièle Hernandez-Verdun, and Valentina Sirri
JCS 2009 122: 489-498. [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?