Yi QiFollow

Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




Shantá D. Hinton

Committee Members

M. Drew LaMar

Daniel Vasiliu


MK-STYX [MAPK (mitogen-activated protein kinase) phosphoserine/threonine/tyrosine-binding protein] and STYX (serine/threonine/tyrosine-interacting protein) are both pseudophosphatase members of the dual-specificity (DUSP) subfamily of protein tyrosine phosphatases. They are catalytically inactive due to mutations at critical residues in their signature motifs. The histidine and cysteine residues of MK-STYX are replaced by phenylalanine and serine, and the cysteine residue of STYX is substituted by a glycine. Nonetheless, they both have significant roles in cell signaling. MK-STYX has been reported to regulate stress granule formation, neurite formation, and apoptosis. STYX is an important signaling molecule in spermatogenesis, the SCF-dependent ubiquitination activity, and the MAPK/ERK pathway. Recent studies show that MK-STYX and STYX are oncogenes marked in glioblastoma and breast cancer, respectively. Our study analyzes the significance of MK-STYX and STYX by measuring and comparing their evolutionary conservation. Their phylogenetic trees were constructed to show any deviation from the species evolutionary paths. Data was collected on a large set of proteins that have either one of MK-STYX’s two domains, the dual-specificity (DUSP) domain and the cdc-25 homology (CH2) /rhodanese-like domain. Then, we calculated the distance between species pair for MK-STYX and STYX’s protein sequence and Ka/Ks ratio and ranked them among the larger set of related proteins, including MK-STYX’s active homologs MKP1 and MKP3. MK-STYX has one of the highest species-species protein distances, and it is under weaker purifying selection pressure than most proteins with its domains. In comparison, the protein distances of STYX are lower than 82% of the DUSP-containing proteins, and it is under one of the strongest purifying selection pressures. Furthermore, we also demonstrate that there is similar selection pressure on their N- and C-terminal sequences. Our study reveals striking distinctions between the evolutionary patterns of MK-STYX and STYX and provides evidence to further explore MK-STYX’s properties.

Available for download on Thursday, May 14, 2026

On-Campus Access Only