生物谷：本周Science發(fā)表兩篇文章有關RNAi技術抑制異源性染色體沉默的機理,，這一機理的揭示有助于將RNAi技術推向應用,。生物谷向大家推薦這兩篇文獻,，以示RNAi最新進展,。
Heterochromatic Silencing and HP1 Localization in Drosophila Are Dependent on the RNAi Machinery
Manika Pal-Bhadra, Boris A. Leibovitch, Sumit G. Gandhi, Madhusudana Rao, Utpal Bhadra, James A. Birchler, and Sarah C. R. Elgin
Science Jan 30 2004: 669-672.
Genes normally resident in euchromatic domains are silenced when packaged into heterochromatin, as exemplified in Drosophila melanogaster by position effect variegation (PEV). Loss-of-function mutations resulting in suppression of PEV have identified critical components of heterochromatin, including proteins HP1, HP2, and histone H3 lysine 9 methyltransferase. Here, we demonstrate that this silencing is dependent on the RNA interference machinery, using tandem mini-white arrays and white transgenes in heterochromatin to show loss of silencing as a result of mutations in piwi, aubergine, or spindle-E (homeless), which encode RNAi components. These mutations result in reduction of H3 Lys9 methylation and delocalization of HP1 and HP2, most dramatically in spindle-E mutants.
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RNAi-Mediated Targeting of Heterochromatin by the RITS Complex
André Verdel, Songtao Jia, Scott Gerber, Tomoyasu Sugiyama, Steven Gygi, Shiv I. S. Grewal, and Danesh Moazed
Science Jan 30 2004: 672-676.
RNA interference (RNAi) is a widespread silencing mechanism that acts at both the posttranscriptional and transcriptional levels. Here, we describe the purification of an RNAi effector complex termed RITS (RNA-induced initiation of transcriptional gene silencing) that is required for heterochromatin assembly in fission yeast. The RITS complex contains Ago1 (the fission yeast Argonaute homolog), Chp1 (a heterochromatin-associated chromodomain protein), and Tas3 (a novel protein). In addition, the complex contains small RNAs that require the Dicer ribonuclease for their production. These small RNAs are homologous to centromeric repeats and are required for the localization of RITS to heterochromatic domains. The results suggest a mechanism for the role of the RNAi machinery and small RNAs in targeting of heterochromatin complexes and epigenetic gene silencing at specific chromosomal loci.
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