Montpetit (Ph.D. University of British Columbia)
Adjunct Assistant Professor
Department of Viticulture and Enology
University of California, Davis
Phone: (530) 752-5955
- Canada Research Chair in RNA Transport
mRNA export is an essential task in all eukaryotes due to the compartmentalization of the cell. Yet, despite the vital significance of this process to the gene expression program, many basic fundamental questions remain. These include:
How does an mRNA transit through the nuclear pore complex?
What proteins are involved in mRNA export?
How is mRNA export regulated in response to stress?
The Montpetit Lab is studying these fundamental cell biology questions with the goal of describing how components of the NPC direct and regulate mRNA export at a cellular, molecular and atomic level. Ultimately, this will allow us to better understand the interplay between nuclear mRNA export and the cellular gene expression program.
The eukaryotic genome is encapsulated by a double membrane bi-layer, which functions to protect and organize the genetic material. However, the presence of a physical barrier that separates events occurring in the nucleus and cytoplasm makes the transport of cargo (e.g. protein and RNA) across the nuclear envelope essential. To accomplish this, material is transported through nuclear pore complexes, which comprise one of the largest macromolecular assemblies in eukaryotic cells with an estimated mass of >60 MDa in yeast. NPCs are inserted into the nuclear envelope at fusion sites between the inner and outer nuclear membranes forming channels with eight-fold rotational symmetry. Cargo is directionally transported through these channels via interactions with soluble transport factors that permit passage through the pore. In the case of mRNA, work in different model systems has provided convincing evidence that Mex67/TAP is the major mRNA export receptor in eukaryotes. However, directional mRNA transport also depends on additional NPC proteins, including the cytoplasmically oriented nucleoporins Nup159, Gle1, and the conserved DEAD-box ATPase Dbp5. Interestingly, mutations in these and other transport proteins are associated with multiple human diseases (e.g. cancer and motor neuron syndromes) and can also be a target for the activity of viral proteins upon infection. Therefore, it is the hope that our research will provide a better understanding of how alterations in mRNA export can result in specific human pathologies.
In this movie, the mRNA export factor Gle1 (yellow) together with the small molecule IP6 binds to Dbp5 (green and blue-grey) triggering the release of RNA (orange). The movie then plays in reverse to illustrate how Dbp5 changes its conformation to interact with RNA and ATP (magenta). This cycle of RNA-binding and release by Dbp5 is critical for the transport of mRNAs out of the nucleus. Montpetit et al. Nature 2011 Apr 14;472(7342):238-42.
We are currently employing cell biology, biochemistry, structural biology, and single molecule imaging techniques in our studies. Together these approaches provide a unique and exciting opportunity to make critical insights into the mechanism of mRNA export. We perform this research in Saccharomyces cerevisiae due to the genetic, biochemical, and cell biological tools that are available, which in combination with the comprehensive knowledge about NPC function, make budding yeast an extremely powerful model system. Moreover, the high conservation of NPC components and transport machinery make the insights that we gain from our studies directly relevant to all eukaryotes, including humans. In the future, we will expand this work to include mammalian systems where mRNA export can be studied with respect to models of disease.
Single molecule imaging of mRNA export in budding yeast. An mRNA (green, top right) can be seen to exit the nucleus and enter the cytoplasm via transport across the nuclear envelope (marked in red). Montpetit et al. unpublished.
Pi release limits the intrinsic and RNA-stimulated ATPase cycles of DEAD-box protein 5 (Dbp5). Wong E V., Cao W, Vörös J, Merchant M, Modis Y, Hackney DD, Montpetit B, De La Cruz EM. 2015. J Mol Biol. In press.
In vivo single-particle imaging of nuclear mRNA export in budding yeast demonstrates an essential role for Mex67p. C. Smith, A. Lari, C. Derrer et al. (2015). J. Cell Biol. 211 , 1121–1130.
Emerging properties of nuclear RNP biogenesis and export. Marlene Oeffinger and Ben Montpetit. (2015). Curr. Opin. Cell Biol. 34, 46–53.
An Alternative Route for Nuclear mRNP Export by Membrane Budding. Montpetit B, & Weis K. Science. 2012 May 18;336(6083):809-810.
Analysis of DEAD-Box Proteins in mRNA Export. Montpetit B, Seelinger MA, & Weis K. Methods in enzymology. 2012;511:239-54.
A conserved mechanism of DEAD-box ATPase activation by nucleoporins and InsP6 in mRNA export. Montpetit B, Thomsen ND, Helmke KJ, Seeliger MA, Berger JM, Weis K. Nature. 2011 Apr 14;472(7342):238-42. Epub 2011 Mar 27.
Regulators of yeast endocytosis identified by systematic quantitative analysis. Burston HE, Maldonado-Báez L, Davey M, Montpetit B, Schluter C, Wendland B, Conibear E. J Cell Biol. 2009 Jun 15;185(6):1097-110. Epub 2009 Jun 8.
Identification of the novel TRAPP associated protein Tca17. Montpetit B, Conibear E. Traffic. 2009 Jun;10(6):713-23. Epub 2009 Feb 11.
Correlation between the secondary structure of pre-mRNA introns and the efficiency of splicing in Saccharomyces cerevisiae. Rogic S, Montpetit B, Hoos HH, Mackworth AK, Ouellette BF, Hieter P. BMC Genomics. 2008 Jul 29;9:355.
Sumoylation of the budding yeast kinetochore protein Ndc10 is required for Ndc10 spindle localization and regulation of anaphase spindle elongation. Montpetit B, Hazbun TR, Fields S, Hieter P. J Cell Biol. 2006 Aug 28;174(5):653-63. Epub 2006 Aug 21.
The kinetochore and cancer: what's the connection? Yuen KW, Montpetit B, Hieter P. Curr Opin Cell Biol. 2005 Dec;17(6):576-82. Epub 2005 Oct 17. Review.
Genome-wide synthetic lethal screens identify an interaction between the nuclear envelope protein, Apq12p, and the kinetochore in Saccharomyces cerevisiae. Montpetit B, Thorne K, Barrett I, Andrews K, Jadusingh R, Hieter P, Measday V. Genetics. 2005 Oct;171(2):489-501. Epub 2005 Jul 5.
The FA2 gene of Chlamydomonas encodes a NIMA family kinase with roles in cell cycle progression and microtubule severing during deflagellation. Mahjoub MR, Montpetit B, Zhao L, Finst RJ, Goh B, Kim AC, Quarmby LM. J Cell Sci. 2002 Apr 15;115(Pt 8):1759-68.
Functional cloning and characterization of a novel nonhomeodomain protein that inhibits the binding of PBX1-HOX complexes to DNA. Abramovich C, Shen WF, Pineault N, Imren S, Montpetit B, Largman C, Humphries RK. J Biol Chem. 2000 Aug 25;275(34):26172-7.