Oral Presentation Australasian Society for Immunology Annual Scientific Meeting 2014

Roquin binds microRNA-146a and Argonaute2 and regulates microRNA homeostasis in T cells  (#19)

Monika Srivastava 1 , Guowen Duan 1 , Nadia Kershaw 2 , Vicki Athanasopoulos 1 , Janet H.C. Yeo 3 , Desheng Hu 4 , Simon H. J. Brown 5 , Slobodan Jergic 5 , Vigo Heissmeyer 4 , Nicholas E. Dixon 5 , Mark M.W. Chong 3 , Jeffrey J. Babon 2 , Carola G. Vinuesa 1
  1. The John Curtin School of Medical Research, ACTON, ACT, Australia
  2. Division of Structural Biology, Walter and Eliza Hall Institute, Melbourne , VIC 3052, Australia
  3. Genomics and Immunology laboratory, St Vincent’s Institute of Medical Research , Melbourne, VIC 3065, Australia
  4. Helmholtz Zentrum München, Institute of Molecular Immunology , München-D-81377, Germany
  5. Centre for Medical and Molecular Bioscience, University of Wollongong and Illawarra , Health and Medical Research Institute, Wollongong, NSW 2522, Australia

Sanroque (Roquinsan) mice with a point mutation in Roquin1 genedevelops autoimmunity due to failed post transcriptional regulation of its target mRNAs (Yu et al, Nature, 2007). ROQUIN-1 is an RNA binding protein that is highly conserved and expressed ubiquitously. The role of posttranscriptional regulators like miRNAs is emerging to be critical in many autoimmune disorders. miRNAs are small 20-22nt that regulate their target mainly by mRNA decay or translational inhibition. They are transcribed as Primary transcript in the nucleus and cleaved by Drosha to produce shorter Precursor miRNAs. Dicer cleaves precursor miRNAs in the cytoplasm and generates the terminal functional form of miRNAs, known as mature miRNAs. The paradoxical increase of miRNAs along with their target mRNAs in Sanroque mice lead us to investigate the role of Roquin in miRNA biogenesis and regulation of its target via miRNAs.

We compared the miRNA expression profile of T cells in mutant and wt mice using miRNA microarray and found while many miRNAs are upregulated in the mutant mice, none of them are downregulated. We further showed that the accumulation of these miRNAs were Dicer dependent and Roquin enhances Dicer-mediated processing of pre-miR-146a. Roquin also directly binds Argonaute2, a central component of the RNA-induced silencing complex, and miR-146a, a microRNA that targets Icos mRNA. In the absence of functional Roquin, miR-146a accumulates in T cells. Its accumulation is not due to increased transcription or processing, rather to enhanced stability of mature miR-146a. This is associated with decreased 3’ end uridylation of the miRNA. Crystallographic studies reveal that Roquin contains a previously unidentified HEPN domain and identify the structural basis of the ‘san’ mutation and Roquin’s ability to bind multiple RNAs. Roquin emerges as a protein that can bind Ago2, miRNAs and target mRNAs, to control homeostasis of both RNA species. 

 We have identified a unique role of an essential autoimmune regulator, Roquin in maintaining miRNA stability and homeostasis in T lymphocytes. 

  1. Roquin represses autoimmunity by limiting inducible T-cell co-stimulator messenger RNA Di Yu, Andy Hee-Meng Tan, Xin Hu, Vicki Athanasopoulos, Nicholas Simpson, Diego G. Silva, Andreas Hutloff, Keith M. Giles, Peter J. Leedman, Kong Peng Lam, Christopher C. Goodnow & Carola G. Vinuesa