Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




Shantà D. Hinton

Committee Members

Lizabeth A. Allsion

Mark S. Forsyth

Kristin L. Wustholz


The pseudophosphatase MK-STYX (mitogen activated protein kinase phosphoserine/threonine/tyrosine binding protein) is a member of the MAPK phosphatase (MKP) family. However, MK-STYX has the amino acid sequence FSX5R in its active site instead of the sequence HCX5R present in other protein tyrosine phosphatases. The replacement of the critical cysteine residue with a serine renders MK-STYX catalytically inactive as a phosphatase. The Hinton Lab previously reported that MK-STYX interacts with the RNA binding protein Ras-GTPase SH3 domain binding protein-1 (G3BP1) in the stress response pathway. During the stress response, mRNA translation is halted, and stress granules, which are cytoplasmic aggregates of mRNA and mRNA binding proteins, are formed. G3BP1 serves as a major structural component of these stress granules. Additionally, microtubules and their associated proteins transport stress granule components to the correct places during the initial stages of assembly. Many proteins that move along microtubules to stress granules, including G3BP1, require the activity of two proteins: dynein and lysine deacetylase 6 (KDAC6). KDAC6 is responsible for facilitating the transport of ubiquitinylated proteins by dynein. Additionally, it regulates microtubule reorganization through the deacetylation of polymerized microtubules. Dynein motility and localization can be affected by several proteins and alteration of these two dynamics may affect stress granule formation. MK-STYX decreases stress granule assembly, however, it does so independently of G3BP1 phosphorylation status at serine 149 which has been reported to induce stress granule formation. Given the essential nature of G3BP1’s interaction with KDAC6 and dynein, we decided to investigate what effects if any that MK-STYX is having on the two proteins. Because KDAC6 deacetylase activity has been shown to affect stress granule assembly, we investigated whether MK-STYX influenced KDAC6 deacetylation. KDAC6 activity assay pilot studies indicate that KDAC6 deacetylase activity is unaffected by the presence of MK-STYX. To further understand the interaction between MK-STYX and dynein, we transfected HEK-293 cells with fluorophore conjugated constructs and studied their localization. Dynein appears to colocalize with MK-STYX. Additionally, dynein localizes to aggregates in the presence of MK-STYX. We have previously demonstrated that MK-STYX does not localize to G3BP1-induced stress granules, so these dynein aggregates may be a novel way of controlling dynein activity.

Available for download on Sunday, May 12, 2030

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