miRNA Proxy Approach

miRNA Proxy Hypothesis

miRNAs, or miRs, are short non-coding RNA strands that bind to mRNAs to regulate gene expression. Our miRNA proxy hypothesis states that:

“if a miR drives a specific biological phenotype, the targets of that miR will drive the same biological phenotype. Thus, miRs can be used to identify (by proxy) the biological functions of specific glycosylation enzymes (or other proteins).”

With this, we may be able to identify crucial glycosylation enzymes driving disease states. Additionally, our research provides novel insight into the precise control miRs have over protein expression – that is, miRs also have the capability of activating gene expression.

Regulation of Glycosylation via miRNAs

Protein glycosylation is one of the most abundant post-translational modifications. It helps to generate the enormous biological complexities inherent in our growth and survival. Our lab has shown that glycosylation is a major target of miR-based regulation (1, 2). This regulation can be used to identify changes in the protein expression of glycosylation genes (glycogenes) that drive specific biological processes (3, 4).

Our lab is working on extending our miRNA proxy approach to predict glycosylation changes driving biological changes using multi-miR networks, including melanoma metastasis and pathogen response. To this end, we created a new high-throughput technology for validating miRNA:mRNA interactions, miRFluR (5). This technology enables the rapid analysis of all miR interactions with the 3'-UTR of a single gene.

Fluorescent ratiometric assay to identify miR:3′-UTR interactions (miRFluR)

Unexpected Upregulation by miRNA

The dominant view is that miRs downregulate protein levels either by promoting mRNA degradation or inhibiting translation. However, we identified miRs that were potential upregulators (up-miRs) of the gene B3GLCT, suggesting a new, differential mode of mRNA regulation (5). Likewise, miR activation of protein expression had only been shown to occur in nondividing cells but our most recent study found that the majority of miR hits for the gene ST6GAL1 upregulated protein expression in proliferating cells (6). This finding turns our current understanding of miR regulation on its head and may offer an explanation for why miRs that upregulate this gene are high in many cancers, as is the level of α-2,6-sialylation for which ST6GAL1 is responsible.

References

Agrawal, P.; Kurcon, T.; Pilobello, K.T.; Rakus, J.F.; Koppolu, S.; Liu, Z.; Batista, B.S.; Eng, W.S., Hsu, K.-L.; Liang, Y.; Mahal, L.K. Mapping post-transcriptional regulation of the human glycome uncovers microRNA defining the glycocode. Proc. Natl. Acad. Sci., USA, 2014, 111, 4338-43. doi: 10.1073/pnas.1321524111
Kasper, B.T.; Koppolu, S.; Mahal, L.K. Insights into miRNA regulation of the human glycome. Biochem. Biophys. Res. Commun., 2014, 445, 774-9. doi: 10.1016/j.bbrc.2014.01.034
Kurcon, T.; Liu, Z.; Paradkar, A.V.; Vaiana, C.A.; Koppolu, S.; Agrawal, P.; Mahal, L.K. miRNA proxy approach reveals hidden functions of glycosylation. Proc. Natl. Acad. Sci., USA, 2015, 112, 7327-32. doi: 10.1073/pnas.1502076112
Vaiana, C.A.; Kurcon, T.; Mahal, L.K. MicroRNA-424 predicts a role for β-1,4 branched glycosylation in cell cycle progression. J. Biol. Chem., 2016, 291, 1529-37. doi: 10.1074/jbc.M115.672220
Thu, T.C.; Chung, J.Y.; Dhawan, D.; Vaiana, C.A.; Mahal, L.K. High-throughput miRFluR platform identifies miRNA regulating B3GLCT that predict Peters’ Plus Syndrome phenotype, supporting the miRNA proxy hypothesis. ACS Chemical Biology, 2021, 16, 1900-1907. doi: 10.1021/acschembio.1c00247. Formerly bioRixv doi: 10.1101/2021.04.01.43813
Jame-Chenarboo, F.; Ng, H.H.; Macdonald, D.; Mahal, L.K. High-throughput analysis reveals miRNA upregulating α-2,6-sialic acid through direct miRNA–mRNA interactions. ACS Central Science, 2022, in Press. doi: 10.1021/acscentsci.2c00748. Formerly bioRixv doi: 10.1101/2022.04.01.486772

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F.A.Q.

What is the Canada Excellence Research Chair?

The Canada Excellence Research Chairs (CERC) Program awards universities up to $10 million over seven years to support world‑renowned researchers and their teams to establish ambitious research programs at Canadian universities.

Where is the University of Alberta?

Located in beautiful Edmonton, Alberta, Canada, the Chemistry Department at the UofA is renown for its active research. It is one of the best equipped and well funded departments in Canada.

What is lectin microarray technology?

It is a glycomic technology developed in the Mahal Lab, provide a rapid analysis of the glycome (1-3). These microarrays utilize immobilized carbohydrate-binding proteins at high spatial density to give specific information on the repertoire of glycans present.

Why study microRNA regulation of glycosylation?

miRNA can be used to identify glycosylation enzymes and their corresponding glycans that drive disease states.

How do I apply for grad school?

At the UofA, you do not have to find a supervisor in order to apply. The department has a process in place for students to find a supervisor and join a research group once they arrive to start their program. However, it is recommended for applicants to contact chemistry faculty members whose areas of research are of interest to you. Information about requirements and how to apply can be found here.