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Science 24 October 2008:
Vol. 322. no. 5901, pp. 602 - 606
DOI: 10.1126/science.1164029
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Reports

Splicing Factors Facilitate RNAi-Directed Silencing in Fission Yeast

Elizabeth H. Bayne,1 Manuela Portoso,1* Alexander Kagansky,1 Isabelle C. Kos-Braun,1 Takeshi Urano,2 Karl Ekwall,3 Flavia Alves,1 Juri Rappsilber,1 Robin C. Allshire1{dagger}

Heterochromatin formation at fission yeast centromeres is directed by RNA interference (RNAi). Noncoding transcripts derived from centromeric repeats are processed into small interfering RNAs (siRNAs) that direct the RNA-induced transcriptional silencing (RITS) effector complex to engage centromere transcripts, resulting in recruitment of the histone H3 lysine 9 methyltransferase Clr4, and hence silencing. We have found that defects in specific splicing factors, but not splicing itself, affect the generation of centromeric siRNAs and consequently centromeric heterochromatin integrity. Moreover, splicing factors physically associate with Cid12, a component of the RNAi machinery, and with centromeric chromatin, consistent with a direct role in RNAi. We propose that spliceosomal complexes provide a platform for siRNA generation and hence facilitate effective centromere repeat silencing.

1 Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, 6.34 Swann Building, Edinburgh EH9 3JR, UK.
2 Department of Biochemistry, Shimane University Faculty of Medicine, 89-1 Enya-cho, Izumo 693-8501, Japan.
3 Karolinska Institute, Department of Biosciences and Medical Nutrition, University College Sodertorn, Novum 141, 57 Huddinge, Sweden.

* Present address: Institute of Human Genetics, 141 rue de la Cardonille, 34396 Montpellier, France.

{dagger} To whom correspondence should be addressed. E-mail: robin.allshire{at}ed.ac.uk

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Altered interactions within FY/AtCPSF complexes required for Arabidopsis FCA-mediated chromatin silencing.
D. Manzano, S. Marquardt, A. M. E. Jones, I. Baurle, F. Liu, and C. Dean (2009)
PNAS 106, 8772-8777
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