RevCen explained

RevCen
Symbol:	RevCen
Rna Type:	Gene; pre-miRNA
Tax Domain:	Schizosaccharomyces

RevCen is a family of non-coding RNA found in Schizosaccharomyces. It is a megastructure containing several siRNA which use the RNAi pathway to regulate heterochromatin formation. The long RNA transcript forms a secondary structure with several stem-loops which are processed by dicer into siRNA. This siRNA then initiate the formation of heterochromatin at the centromeres of fission yeast.^[1] Northern blot analysis confirmed the siRNAs were produced from the large RNA structure RevCen in vivo. As with all siRNAs, the enzyme dicer is responsible for dissecting dsRNA into the 21nt stretch of double-stranded RNA. Human recombinant dicer enzyme processed the RevCen structure in vitro, though the same activity by yeast Dcr1 has not been confirmed.

This is a different mechanism to that involving the well-understood RITS (RNA-induced initiation of transcriptional gene silencing) complex.^{[2] [3]} It has been suggested that both mechanisms work together, with the RevCen structure potentially acting as a backup system when Rdp1-generated double-stranded siRNA precursors are lost.

Further reading

• Book: http://www.horizonpress.com/rnareg. Vavasseur. 2008 . Heterochromatin Assembly and Transcriptional Gene Silencing under the Control of Nuclear RNAi: Lessons from Fission Yeast . RNA and the Regulation of Gene Expression: A Hidden Layer of Complexity . . . 978-1-904455-25-7. etal.
• Sigova A, Rhind N, Zamore PD . A single Argonaute protein mediates both transcriptional and posttranscriptional silencing in Schizosaccharomyces pombe . Genes Dev. . 18 . 19 . 2359–2367 . October 2004 . 15371329 . 522986 . 10.1101/gad.1218004 . 2010-08-17.
• Steiner NC, Hahnenberger KM, Clarke L . Centromeres of the fission yeast Schizosaccharomyces pombe are highly variable genetic loci . Mol. Cell. Biol. . 13 . 8 . 4578–4587 . August 1993 . 8336703 . 360078 . 10.1128/MCB.13.8.4578.
• Takahashi K, Murakami S, Chikashige Y, Niwa O, Yanagida M . A large number of tRNA genes are symmetrically located in fission yeast centromeres . J. Mol. Biol. . 218 . 1 . 13–17 . March 1991 . 2002498 . 10.1016/0022-2836(91)90867-6.

Notes and References

1. Djupedal I, Kos-Braun IC, Mosher RA, etal . Analysis of small RNA in fission yeast; centromeric siRNAs are potentially generated through a structured RNA . EMBO J. . 28 . 24 . 3832–3844 . December 2009 . 19942857 . 10.1038/emboj.2009.351 . 2797062.
2. Sugiyama T, Cam H, Verdel A, Moazed D, Grewal SI . RNA-dependent RNA polymerase is an essential component of a self-enforcing loop coupling heterochromatin assembly to siRNA production . Proc. Natl. Acad. Sci. U.S.A. . 102 . 1 . 152–157 . January 2005 . 15615848 . 544066 . 10.1073/pnas.0407641102 . free .
3. Verdel A, Jia S, Gerber S, etal . RNAi-mediated targeting of heterochromatin by the RITS complex . Science . 303 . 5658 . 672–676 . January 2004 . 14704433 . 10.1126/science.1093686 . 3244756.