1) Intracellular trafficking of telomerase RNA and its role in biogenesis and regulation of its activity

Telomeres protect the ends of chromosomes in eukaryotic cells by preventing their degradation and fusion. In most eukaryotes, telomerase reverse transcriptase is responsible for telomere elongation. This enzyme consists of an RNA subunit containing the template, to which protein subunits responsible for catalytic activity bind. Telomerase plays a crucial role in cell transformation since it is reactivated in the majority of cancers and allows the immortalization of cancer cells. Our laboratory particularly uses single-molecule imaging to explore: 1) the intracellular trafficking of telomerase RNA and its role in the biogenesis of this holoenzyme, as well as 2) the role of non-coding telomeric RNAs in the regulation of telomerase activity.

2) Pathogenesis of Myotonic Dystrophy type 1 (DM1)

DM1 is a rare and incurable neuromuscular genetic disease which affects 1 in 8,000 people. Over time, patients develop lung and heart complications that render them disabled and limit their life expectancy. This disease is caused by the accumulation of CTG triplet repeats in the DMPK gene, which leads to the aggregation of its mRNA as nuclear foci in muscle cells. The current hypothesis of a toxic effect of this mRNA posits that the nuclear retention of the mutant DMPK mRNA alters the function of regulatory RNA-binding proteins, which as sequestered on the mutant transcript. Our laboratory studies 1) the role of non-coding RNAs in the pathogenesis of DM1, 2) aims to identify proteins associated with RNAs containing expanded triplet repeats, and 3) develop pharmacological treatments for this disease.

3) Mechanisms of intracellular transport of mRNAs and their local translation

mRNA localization is used by different types of polarized cells to locally translate specific proteins and thus restrict their distribution to a particular region of the cytoplasm. This mechanism offers the possibility of locally and temporally regulate the expression of proteins. The transport and localization of specific mRNAs plays an important role during the development of multicellular organisms, as well as in biological processes such as synaptic transmission, cell motility and asymmetric cell division. Our laboratory uses the localization of mRNA in the bud of the yeast Saccharomyces cerevisiae as a model organism. We seek to: 1) understand the mechanisms of recognition of localized mRNAs and assembly of the localization machinery on these mRNAs, and 2) identify and characterize the factors responsible for controlling the translation of mRNAs during their transport.

• Laprade H., Querido E., Smith MJ., Guérit D., Crimmins H., Conomos D., Pourret E., Chartrand P., Sfeir A. (2020) Single-molecule imaging of telomerase RNA reveals a Recruitment – Retention model for telomere elongation. Molecular Cell, 79: 115-126.
• Lalonde M., Chartrand P. (2020) TERRA, a multifaceted regulator of telomerase activity at telomeres. Journal of Molecular Biology, 432: 4232-4243.
• Avogaro L., Querido E., Dalachi M., Jantsch MF., Chartrand P., Cusanelli E. (2018) Live-cell imaging reveals the dynamics and function of single-telomere TERRA molecules in cancer cells. RNA Biology, 15: 787-796.
• Ouenzar F., Lalonde M., Laprade H., Morin G., Gallardo F., Chartrand P. (2017) Cell cycle-dependent spatial segregation of telomerase RNA from sites of DNA damage. J. Cell Biology, 216: 2355-2371
• Moradi-Fard S., Sarthi J., Tittel-Elmer M., Lalonde M., Cusanelli E., Chartrand P., Cobb JA. (2016) Smc5/6 is a Telomere-associated complex that regulates Sir4 binding and TPE. PLoS Genetics. 12 e1006268.
• Cusanelli E., Chartrand P. (2015) Telomeric repeat-containing RNA TERRA: a noncoding RNA connecting telomere biology to genome integrity. Frontier in Genetics, 6: 143
• Shahbabian, K., Jeronimo, C., Forget, A., Robert, F., Chartrand, P. (2014) Co-transcriptional recruitment of Puf6 by She2 couples translational repression to mRNA localization. Nucleic Acids Research, 42: 8692-8704.
• Cusanelli E., Perez Romero, C.A., Chartrand P. (2013) Telomeric non-coding RNA nucleates telomerase clusters at short telomeres. Molecular Cell, 51: 780-791.
• Pfingsten, J.S., Goodrich, K.J., Taabazuing, C., Ouenzar, F., Chartrand, P., Cech T.R. (2012) Mutually exclusive binding of telomerase RNA and DNA by yeast Ku: a new model for telomerase recruitment.  Cell. 148: 922-932.
• Querido E., Gallardo F., Beaudoin M., Ménard C., Chartrand P. (2011) Stochastic and reversible aggregation of mRNA with expanded CUG-triplet repeats.  J. Cell Science. 124: 1703-1714.
• Gallardo F., Laterreur N., Cusanelli E., Ouenzar F., Querido E., Wellinger R.J., Chartrand P.  (2011) Live cell imaging of telomerase RNA dynamics reveals cell cycle-dependent clustering of telomerase at elongating telomeres.  Molecular Cell,44: 819-827.
• Shen Z., St-Denis, A., Chartrand P. (2010) Cotranscriptional recruitment of She2p by RNA pol II elongation factor Spt4-Spt5/DSIF promotes mRNA localization to yeast bud.  Genes & Development, 24: 1914-1926
• Shen Z., Paquin N., Forget A., Chartrand P. (2009)  Nuclear shuttling of She2p couples ASH1 mRNA localization to its translational repression by recruiting Loc1p and Puf6p.  Mol. Biol. Cell, 20: 2265-2275.
• Gallardo F., Olivier C., Dandjinou A.T., Wellinger R.J., Chartrand P. (2008) TLC1 RNA nucleo-cytoplasmic trafficking links telomerase biogenesis to its recruitment to telomeres. The Embo J., 27: 748-757.
• Paquin N., Chartrand P. (2008) Local regulation of mRNA translation: new insights from the bud. Trends in Cell Biology, 18: 105-111.
• Paquin N., Ménade M., Poirier G., Donato D., Drouet E., Chartrand P. (2007) Local activation of yeast ASH1 mRNA translation through phosphorylation of Khd1p by the casein kinase Yck1p.  Molecular Cell., 26: 795-809.
• Sylvestre Y., De Guire V., Querido E., Mukhopadhyay U.K., Bourdeau V., Major F., Ferbeyre G., Chartrand P. (2007)  An E2F/miR-20a auto-regulatory feed-back loop. J. Biol. Chem., 282: 2135-2143.
• Olivier C., Poirier G., Gendron P., Boisgontier A., Major F., Chartrand P. (2005) Identification of a conserved RNA motif essential for She2p recognition and mRNA localization to the yeast bud.  Mol. Cell. Biol. 25: 4752-4766.