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ZK858.4 causes embryonic lethality but does not directly impact MEX-3 localization in an RNAi induced knockdown of E3 ubiquitin ligases in Caenorhabditis elegans

by Reichard, Kathryn L.


The ubiquitin proteosome system (UPS) functions in the cell to mark specific proteins for degradation. E3 ubiquitin ligases act as recognition factors and increase the specificity of the UPS. MEX-3 is an RNA binding protein in Caenorhabditis elegans that inhibits the translation of PAL-1, a posterior specifying protein, and contributes to development of the anterior of the embryo. MEX-3 is present throughout the oocyte, 1-cell, and 2-cell embryo. However, MEX-3 is then depleted in the posterior after the second cell division, and PAL-1 is then expressed in the two posterior blastomeres of the 4-cell embryo. MEX-3 is rapidly depleted from the entire embryo after the 8-cell stage. This degradation is location and time specific, and thus hypothesized to be caused by the UPS. MEX-3 is hypothesized to be targeted for degradation by a specific E3 ubiquitin ligase, and knockout of this protein should result in increase in universal MEX-3 expression in the early embryo. This study sought to determine the MEX-3 specific E3 ubiquitin ligase(s). Putative E3 ubiquitin ligases expressed during early embryonic development were knocked out in C. elegans, and phenotypes were determined. Of the knocked-out ligase genes, only one, ZK858.4 caused embryonic lethality at both 15˚ and 24˚ C. However, fluorescence microcopy of GFP::MEX-3 demonstrated that ZK858.4 knockout did not appear to increase global MEX-3 concentrations. Determining which protein targets MEX-3 degradation will provide more insight into the molecular mechanisms of determining anterior/posterior patterning in C. elegans early embryonic development.


Includes bibliographical references.

Administrative Notes


Copyright restrictions apply.
Colorado College
Digital Origin
born digital
45 pages : illustrations (some color)
Senior Thesis -- Colorado College
Thesis Advisor
Huang, Nancy
Department of Biology
Degree Name
Degree Type
Bachelor of Arts
Degree Grantor
Colorado College
Date Issued