Processing of microRNA primary transcripts requires heme in mammalian cells

Sara H. Weitz, Ming Gong, Ian Barr, Shimon Weiss, Feng Guo

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


DiGeorge syndrome critical region gene 8 (DGCR8) is the RNAbinding partner protein of the nuclease Drosha. DGCR8 and Drosha recognize and cleave primary transcripts of microRNAs (pri-miRNAs) in the maturation of canonical microRNAs (miRNAs) in animals. We previously reported that human, frog, and starfish DGCR8 bind heme when expressed in Escherichia coli and that Fe (III) heme activates apoDGCR8 in reconstituted pri-miRNA processing assays. However, the physiological relevance of heme in miRNA maturation has not been clear. Here, we present a live-cell pri-miRNA processing assay that produces robust signals and faithfully indicates DGCR8 and Drosha activities. We demonstrate that all known heme-binding-deficient DGCR8 mutants are defective in pri-miRNA processing in HeLa cells. DGCR8 contains a previously uncharacterized heme-binding motif, "IPCL," that is also required for its activity. Heme availability and biosynthesis in HeLa cells positively affect primiRNA processing and production of mature miRNA. These results establish an essential function for heme in pri-miRNA processing in mammalian cells. Our study suggests that abnormal heme biosynthesis and degradation may contribute to diseases via miRNAmediated gene regulation networks.

Original languageEnglish
Pages (from-to)1861-1866
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number5
StatePublished - 4 Feb 2014
Externally publishedYes


  • Fluorescence microscopy
  • Iron
  • Noncoding RNA
  • Protoporphyrin IX
  • RNA processing


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