SAD-2 is required for meiotic silencing by unpaired DNA and perinuclear localization of SAD-1 RNA-directed RNA polymerase
- Patrick K. T. Shiu*,†,
- Denise Zickler‡,
- Namboori B. Raju§,
- Gwenael Ruprich-Robert‡, and
- Robert L. Metzenberg†,¶
- *Division of Biological Sciences, University of Missouri, Columbia, MO 65211;
- ‡Institut de Génétique et Microbiologie, Université Paris-Sud, 91405 Orsay Cedex, France;
- §Department of Biological Sciences, Stanford University, Stanford, CA 94305; and
- ¶Department of Biology, California State University, Northridge, CA 91330
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Edited by David D. Perkins, Stanford University, Stanford, CA, and approved December 7, 2005 (received for review October 11, 2005)
Abstract
A gene unpaired during the meiotic homolog pairing stage in Neurospora generates a sequence-specific signal that silences the expression of all copies of that gene. This process is called Meiotic Silencing by Unpaired DNA (MSUD). Previously, we have shown that SAD-1, an RNA-directed RNA polymerase (RdRP), is required for MSUD. We isolated a second gene involved in this process, sad-2. Mutated Sad-2 RIP alleles, like those of Sad-1, are dominant and suppress MSUD. Crosses homozygous for Sad-2 are blocked at meiotic prophase. SAD-2 colocalizes with SAD-1 in the perinuclear region, where small interfering RNAs have been shown to reside in mammalian cells. A functional sad-2 + gene is necessary for SAD-1 localization, but the converse is not true. The data suggest that SAD-2 may function to recruit SAD-1 to the perinuclear region, and that the proper localization of SAD-1 is important for its activity.
Footnotes
- †To whom correspondence may be addressed. E-mail: shiup{at}missouri.edu or rmetzenberg{at}yahoo.com
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Author contributions: P.K.T.S. and R.L.M. designed research; P.K.T.S., D.Z., N.B.R., G.R.-R., and R.L.M. performed research; P.K.T.S. and R.L.M. contributed new reagents/analytical tools; P.K.T.S., D.Z., N.B.R., and R.L.M. analyzed data; and P.K.T.S., D.Z., and R.L.M. wrote the paper.
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Conflict of interest statement: No conflicts declared.
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This paper was submitted directly (Track II) to the PNAS office.
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Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AY303388).
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See Commentary on page 2007.
- Abbreviations:
- RNAi,
- RNA interference;
- RIP,
- repeat-induced point mutation;
- siRNA,
- small interfering RNA;
- RFP,
- red fluorescent protein;
- RdRP,
- RNA-directed RNA polymerase.
Abbreviations:
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Freely available online through the PNAS open access option.
- © 2006 by The National Academy of Sciences of the USA
