All ETDs from UAB

Advisory Committee Chair

David F Crawford

Advisory Committee Members

Daniel C Bullard

Xinbin Chen

Weei-Chin Lin

Lawrence S Prince

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine


A microarray study was performed which identified G2E3 as a novel, putative ubiquitin ligase that was both G2/M-specific in expression and down regulated at the transcriptional level following DNA damage by γ-irradiation. The initial characterization of this protein is described herein. G2E3 is composed of three PHD/RING (plant homoedomain/really interesting new gene) domains within its amino-terminal half and a carboxy-terminal HECT (homologous to E6AP carboxy-terminus) domain. G2E3 is regulated in part by its subcellular localization. The protein normally resides within the nucleoplasm of cultured cells and distinctly within the nucleolus of HeLa cells. G2E3 is a nucleo-cytoplasmic shuttling protein with its nuclear export mediated by a novel, CRM1-independent nuclear export domain located within the HECT domain. Furthermore, in response to DNA damage, G2E3 rapidly delocalizes from the nucleolus of HeLa cells. In vitro ubiquitination experiments demonstrate that G2E3 is able to mediate auto-ubiquitination and that this activity is dependent upon the third PHD/RING domain. To examine the function of G2E3 in vivo, a knockout mouse model has been generated. G2E3 heterozygous animals develop normally and display no overt defects. However, G2E3 knockout animals die prior to embryonic day 8.5. Northern blotting demonstrates that G2E3 is expressed throughout development, and β-galactosidase staining indicates those tissues where the protein is most predominantly expressed. iii These experiments demonstrate that G2E3 is a highly regulated ubiquitin ligase that is required for mammalian embryonic development.



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