Fusion and Wildtype Proteins of EWSR1 Interact in a Protein Granule
AuthorAhmed, Nasiha Salma
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractEwing sarcoma is driven by fusion proteins containing a low complexity (LC) domain that is intrinsically disordered and a powerful transcriptional regulator. The most common fusion protein found in Ewing sarcoma, EWS-FLI1, takes its LC domain from the RNA-binding protein EWSR1 (Ewing Sarcoma RNA-binding protein 1) and a DNA-binding domain from the transcription factor FLI1 (Friend Leukemia Virus Integration 1). The LC domain in EWS-FLI1 can bind RNA polymerase II (RNA Pol II) and can self-assemble through a process known as phase separation. The ability of EWSR1 and related RNA-binding proteins to assemble into ribonucleoprotein granules in cells has been intensely studied but the role of phase separation in EWS-FLI1 activity is less understood. We investigated the overlapping functions of EWSR1 and EWS-FLI1 in controlling gene expression and tumorigenic cell growth in Ewing sarcoma, and our results suggested that these proteins function closely together. We then studied the nature of interactions among EWS-FLI1, EWSR1, and RNA Pol II. We observed EWSR1 and RNA Pol II to be present in protein granules in cells. We then identified protein granules in cells associated with the fusion protein, EWS-FLI1. The tyrosine residues in the LC domain are required for the abilities of EWS-FLI1 to bind its partners, EWSR1 and RNA Pol II, and to incorporate into protein granules. These data suggest that interactions among EWS-FLI1, RNA Pol II, and EWSR1 in Ewing sarcoma can occur in the context of a molecular scaffold found within protein granules in the cell.
Degree ProgramGraduate College
Molecular & Cellular Biology
Degree GrantorUniversity of Arizona
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Protein stickiness, rather than number of functional protein-protein interactions, predicts expression noise and plasticity in yeastBrettner, Leandra M.; Masel, Joanna; Present address: Ecology & Evolutionary Biology, University of Arizona, 1041 E Lowell St, Tucson, AZ, 85721, USA; Present address: Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA (BioMed Central, 2012)BACKGROUND:A hub protein is one that interacts with many functional partners. The annotation of hub proteins, or more generally the protein-protein interaction "degree" of each gene, requires quality genome-wide data. Data obtained using yeast two-hybrid methods contain many false positive interactions between proteins that rarely encounter each other in living cells, and such data have fallen out of favor.RESULTS:We find that protein "stickiness", measured as network degree in ostensibly low quality yeast two-hybrid data, is a more predictive genomic metric than the number of functional protein-protein interactions, as assessed by supposedly higher quality high throughput affinity capture mass spectrometry data. In the yeast Saccharomyces cerevisiae, a protein's high stickiness, but not its high number of functional interactions, predicts low stochastic noise in gene expression, low plasticity of gene expression across different environments, and high probability of forming a homo-oligomer. Our results are robust to a multiple regression analysis correcting for other known predictors including protein abundance, presence of a TATA box and whether a gene is essential. Once the higher stickiness of homo-oligomers is controlled for, we find that homo-oligomers have noisier and more plastic gene expression than other proteins, consistent with a role for homo-oligomerization in mediating robustness.CONCLUSIONS:Our work validates use of the number of yeast two-hybrid interactions as a metric for protein stickiness. Sticky proteins exhibit low stochastic noise in gene expression, and low plasticity in expression across different environments.
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