Nature Structural & Molecular Biology
- 13, 1097 - 1101 (2006)
Published online: 12 November 2006; | doi:10.1038/nsmb1167
RNA polymerase III transcribes human microRNAsGlen M Borchert1, 2, William Lanier2, 3 & Beverly L Davidson1, 4, 51
Department of Internal Medicine, University of Iowa, Iowa City, Iowa 52242, USA. 2
Genetics Training Program, University of Iowa, Iowa City, Iowa 52242, USA. 3
Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242, USA. 4
Department of Neurology, University of Iowa, Iowa City, Iowa 52242, USA. 5
Department of Physiology & Biophysics, University of Iowa, Iowa City, Iowa 52242, USA.
Correspondence should be addressed to Beverly L Davidson beverly-davidson@uiowa.edu Prior work demonstrates that mammalian microRNA (miRNA or miR) expression requires RNA polymerase II (Pol II). However, the transcriptional requirements of many miRNAs remain untested. Our genomic analysis of miRNAs in the human chromosome 19 miRNA cluster (C19MC) revealed that they are interspersed among Alu repeats. Because Alu transcription occurs through RNA Pol III recruitment, and we found that Alu elements upstream of C19MC miRNAs retain sequences important for Pol III activity, we tested the promoter requirements of C19MC miRNAs. Chromatin immunoprecipitation and cell-free transcription assays showed that Pol III, but not Pol II, is associated with miRNA genomic sequence and sufficient for transcription. Moreover, the mature miRNA sequences of approximately 50 additional human miRNAs lie within Alu and other known repetitive elements. These findings extend the current view of miRNA origins and the transcriptional machinery driving their expression.
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