RNA polymerase IV

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RNA polymerase IV is an enzyme which synthesizes small interfering RNA (siRNA) in plants.[1] Polymerase IV is specific to plants genomes and is required for the synthesis of over 90% of 24-nt heterochromatic siRNA. [2]


RNA polymerase silences the transposons and repetitive DNA in the siRNA pathway.[1] The siRNA plays a major role in defending the genome against the invading viruses and transposable elements by RNA directed DNA methylation. [2]

Polymerase IV and ROS1 demethylase unlocks and recondenses the 5S rDNA chromatin, which is present in seed and used for the development of adult features in plants. [3] Polymerase IV is involved in setting the methylation patterns in the 5S genes during plant maturation. [3]

In arabidopsis polymerase IV works with binding protein DCL3 and a RNA polymerase II RDR2 in a silencing pathway which Polymerase IV would produce RNA, which is changed to dsRNA by RDR2 then converted to siRNA by DCL3.[1]


  1. ^ a b c Herr, A. J. , M. B. Jensen, T. Dalmay, and D. C. Baulcombe (2005). "RNA Polymerase IV Directs Silencing of Endogenous DNA". Science. 308 (5718): 118–20. PMID 15692015. doi:10.1126/science.1106910. 
  2. ^ a b Zhang, Xiaoyu, Ian R. Henderson, Cheng Lu, Pamela J. Green, and Steven E. Jacobsen (2007). "Role of RNA polymerase IV in plant small RNA metabolism". Proc Natl Acad Sci USA. 104. doi:10.1073/pnas.0611456104. 
  3. ^ a b Douet, Julien , Bertrand Blanchard, Claudine Cuvillier, and Sylvette Tourmente (2008). "Interplay of RNA Pol IV and ROS1 During Post-Embryonic 5S rDNA Chromatin Remodeling". Plant and Cell Physiology. 49.