Gracjan Michlewski

Lab members

Nila Roy Choudhury, Gregory Heikel, Angela Downie, Ruiz Velasco

Regulation of RNA processing and function

The regulation of RNA processing by RNA-binding proteins (RBPs) is at the functional heart of all cells. RNA-binding proteins mediate and control gene expression by regulating mRNA splicing, localisation, translation and decay, as well as miRNA maturation and  function. Consequently, they contribute to cellular homeostasis, normal development and disease. Importantly, new classes of RNA-binding proteins, such as E3 ubiquitin ligases, kinases  and phosphatases, which I collectively describe as RNA-binding protein-modifying (RBPM) enzymes, have recently been discovered by high-throughput proteomics. This suggests the exciting possibility that RBPM enzymes may regulate RNA processing. Our aim is to study these proteins in the context of RNA biology, gene expression and disease.

Recently, we have discovered that the E3 ubiquitin ligase Trim25, which is a key factor in innate immune response to RNA viruses, recognises let-7a miRNA precursor (pre-let-7a-1) and regulates its stability (Choudhury NR et al. Cell Rep. 2014). Trim25 is a novel RNA-binding protein and a member of the Tripartite Motif (TRIM) family of E3 ubiquitin ligases. Trim25 plays a pivotal role in innate immune response to RNA viruses. RNA viruses have caused most21st century epidemics, including Influenza A, which annually kills 250,000 to 500,000 people (World Health Organisation). RNA viruses such as Influenza A, Ebola, or SARS, produce RNA molecules that are recognised by the Retinoic acid-inducible gene I (RIG-I), which undergoes Trim25-mediated ubiquitination. This ubiquitination triggers signalling pathways that culminate in the expression of type I interferon and anti-viral response. Knowledge about the RNA-related functions of Trim25 in the regulation of viral RNA-mediated signalling remains rudimentary. Thus, my projects are providing crucial insights into biology of the cell as well as anti-viral defence mechanisms.

Despite the essential involvement of RNA-protein complexes in mediating and controlling every step of gene expression and RNA-mediated innate immune signalling pathways, the molecular mechanisms of their spatial and temporal regulation is still poorly understood.  Our approach, combining molecular, cellular, structural and synthetic biology, will reveal how Trim25, provides additional layers of control over canonical RNA-binding proteins   anddefine their functions in physiological conditions and upon viral infection. The outcome of this research could redefine our understanding of the control of RNA processing and signaling  and has the potential to transform the field of RNA  biology.

Selected publications:

Trubitsyna, M., Michlewski, G., Finnegan, D., Elfick, A., Rosser, S., Richardson, J., French, C. (2017). Use of mariner transposases for one-step delivery and integration of DNA in prokaryotes and eukaryotes by transfection. Nucleic Acids Res.  gkx113

Nowak, J.S., Hobor, F., Downie Ruiz Velasco, A., Choudhury, N.R., Heikel, G., Kerr, A., Ramos, A., and Michlewski, G. (2017) Lin28a uses distinct mechanisms of binding to RNA and affects positively and negatively miRNA levels. RNA  3:317-332

Choudhury, N.R., Nowak, J. S., Zou J., Rappsilber, J., Spoel H.S., and Michlewski, G. (2014). Trim25 is an RNA-specific activator of Lin28a/TuT4-mediated uridylation. Cell Rep. 9:1-8