What We Do
Viral RNA Decay mRNA Decay in Myotonic Dystrophy mRNA Decay in Stem Cells Nucleophosmin & Polyadenylation
The Wilusz² Lab is run as a close collaboration between Drs. Jeffrey and Carol Wilusz. Our lab is interested in the mechanisms and regulation of mRNA metabolism in eukaryotic cells and how these processes influence pathogenesis of human diseases, including cancer, viral infection and myotonic dystrophy.
Messenger RNA Metabolism
In eukaryotes, the production of a protein involves many more events than transcription of the DNA to produce an mRNA followed by translation of the mRNA to make protein. During transcription, each mRNA undergoes a complex pathway of processing reactions including capping, splicing and polyadenylation (Figure 1). Each of these steps is highly regulated and must occur correctly in order to generate a functional transcript. We believe that upon successful completion of each processing event, the mRNA is "marked" through deposition of various protein complexes to enable the cell to distinguish transcripts that have been correctly processed. Thus, those transcripts that do not bear the appropriate markers - i.e those that have aberrant mRNP conformations - can be readily identified and degraded. One major project in the lab focuses on how and why the oncoprotein nucleophosmin is deposited on mRNAs during polyadenylation.
Messenger RNA turnover
Messenger RNA decay is an often over-looked but highly regulated aspect of gene expression that is integral in determining mRNA levels (Figure 2). Recent studies suggest that as much as 50% of the changes in gene expression that occur in response to certain stimuli are at the level of mRNA stability. As well as being a regulatory process, mRNA decay is also a means to destroy aberrant transcripts at any time in the mRNA life cycle from processing in the nucleus to translation in the cytoplasm.
In eukaryotes, cytoplasmic mRNA decay initiates with removal of the poly(A) tail (deadenylation) (Figure 3). This step can be performed by PARN, a cap-dependent deadenylase, or by other deadenylases such as CCR4/NOT. After deadenylation, mRNAs are degraded by one of two pathways, decapping and 5'-3' exonucleolytic decay or 3'-5' exonucleolytic decay. The 3'-5' pathway is mediated by a large complex of proteins known as the exosome.
Regulation of mRNA Turnover
The rate of decay of an mRNA may be modulated by RNA-binding proteins or miRNAs associated with the transcript. Such factors can recruit or inhibit mRNA decay enzymes and their activity can be regulated by cellular signals. Three projects in the lab are investigating the role of specific factors in regulated mRNA decay. One project is studying how CUGBP1, an RNA-binding protein whose function is disrupted in myotonic dystrophy, regulates decay of specific transcripts. Another project focuses on how viral RNAs evade the mRNA decay machinery by usurping cellular RNA-binding proteins that have stabilizing effects. Finally, we have recently begun investigating mRNA decay mechanisms in pluripotent stem cells.
An in vitro assay for mRNA decay
We have developed and patented an in vitro assay that allows us to recapitulate the various steps of mRNA decay in S100 extracts from multiple cell types including HeLa, Jurkat, trypanosomes and mosquitoes (Figure 4). This assay is integral to many of our research efforts and has been utilized to generate results for more than a dozen publications from our lab as well as being adopted by other labs. Detailed protocols for our in vitro assays are available on this site, and we are happy to offer technical advice.
We are always happy to talk to interested post-docs and graduate students about current projects in the laboratory. We take graduate students from the MIP and Cell & Molecular Biology Programs. In addition, we accept undergraduates for Capstone and Honors projects throughout the year. Contact either Jeff or Carol Wilusz for more information.