Title

Ferric, not ferrous, heme activates RNA-binding protein DGCR8 for primary microRNA processing.

Digital Object Identifier / DOI

https://doi.org/10.1073/pnas.1114514109

Department

Natural Sciences and Mathematics

Document Type

Article

Source

Proceedings of the National Academy of Sciences

Publication Date

2-7-2012

ISSN

1091-6490

Volume

109

Issue

6

First Page

1919

Last Page

1924

Abstract

The RNA-binding protein DiGeorge Critical Region 8 (DGCR8) and its partner nuclease Drosha are essential for processing of microRNA (miRNA) primary transcripts (pri-miRNAs) in animals. Previous work showed that DGCR8 forms a highly stable and active complex with ferric [Fe(III)] heme using two endogenous cysteines as axial ligands. Here we report that reduction of the heme iron to the ferrous [Fe(II)] state in DGCR8 abolishes the pri-miRNA processing activity. The reduction causes a dramatic increase in the rate of heme dissociation from DGCR8, rendering the complex labile. Electronic absorption, magnetic circular dichroism, and resonance Raman spectroscopies indicate that reduction of the heme iron is accompanied by loss of the cysteines as axial ligands. ApoDGCR8 dimers, generated through reduction and removal of the heme, show low levels of activity in pri-miRNA processing in vitro. Importantly, ferric, but not ferrous, heme restores the activity of apoDGCR8 to the level of the native ferric complex. This study demonstrates binding specificity of DGCR8 for ferric heme, provides direct biochemical evidence for ferric heme serving as an activator for miRNA maturation, and suggests that an intracellular environment increasing the availability of ferric heme may enhance the efficiency of pri-miRNA processing.

PubMed ID

22308374

Share

COinS