Date of Award

Fall 2013

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Medicinal Chemistry and Molecular Pharmacology

First Advisor

Richard Gibbs

Committee Chair

Richard Gibbs

Committee Member 1

Jean- Christophe Rochet

Committee Member 2

Laurie Parker

Committee Member 3

Mahdi Abu- Omar


Many proteins require prenylation in order to be biologically functional. Some such proteins include the small Ras and Rho GTPase superfamilies, nuclear lamins A and B, and the kinesin motor proteins CENP-E and F. Prenyltransferase (PTase) inhibition is currently being explored as a possible treatment not only for cancer but for a wide variety of other diseases.

Clinical studies revealed that the effectiveness of farnesyltransferase inhibitors (FTIs) to treat Ras-dependent tumors is determined by which isoform of Ras is overactive. Unfortunately the majority of Ras-dependent tumors have a mutation in either the N- or K-Ras isoforms; both of these isoforms can be alternatively prenylated by GGTase-I and, therefore, do not respond to FTI treatment. This sparked our interest in developing GGTase-I inhibitors and exploring requirements needed for alternative prenylation by GGTase-I.

Clinical studies also brought about the discovery that FTIs were effective toward some Ras-independent tumors (e.g. breast cancer, chronic & acute myeloid leukemia, multiple myeloma, and advanced myelodyplastic syndrome). Presumably, these results are due to the prenylation of one or more essential proteins required for tumorigenesis. The identity of the protein(s) responsible for the observed antitumor affect in Ras-independent tumors remains elusive. Identifying tumors reliant on proteins that are solely prenylated by one prenyltransferase could open up new avenues for therapeutic intervention by FTIs or GGTIs. Thus, identifying

prenylated proteins and the prenyltransferase(s) required for this modification is of great interest and importance.

Chemical tools capable of modulating prenylation of specific proteins would allow researchers to more precisely investigate proteins' individual roles in the cell as well as the function of their lipid moieties. To this end we use a combinatorial approach in which we screen isoprenoid pyrophosphate analogs against a synthetic Dansyl-GCaaX peptide library (the minimal recognition sequence of PTases; Dansyl-G = Dansyl-glycine, C = Cys, a = aliphatic amino acid, X = a small subset of amino acids, which in general designates which PTase modifies the CaaX sequence). This approach revealed that for each pyrophosphate analog, both FTase and GGTase-I exhibit unique patterns of reactivity among various CaaX sequences. Our laboratory has also developed a tagging-via-substrate proteomic method to identify farnesylated proteins within cells. The aim of this research focuses not only on extending our current techniques into the realm of geranylgeranylation in order to study the enzymatic requirements of GGTase-I, but also on developing cellular probes that would allow for the identification of geranylgeranylated proteins.

The initial goal of this project was to advance our knowledge of GGTase-I substrate specificity in terms of both prenyl and protein substrates and to investigate GGTase-I versus FTase substrate specificity. The overall goal of this project was the development of biologically useful chemical tools that could in the future be developed into proteomic probes for GGTase-I in order to identify and characterize geranylgeranylated proteins.