Undergraduate Honors Theses

Thesis Defended

Fall 2011

Document Type



Chemistry & Biochemistry

First Advisor

Dylan Taatjes, PhD


Found in all eukaryotic organisms, the Mediator complex is an essential component of the transcription machinery and acts as a molecular bridge between activators and other general transcription factors. The transcription factor p53 is a potent tumor suppressor and acts as a master controller of the cell cycle and programmed cell death. Binding of p53 to Mediator induces conformational shifts that activate RNA polymerase II transcription. In the wild type form, p53 aides in inhibiting growth of cancerous cells, but this is not the effect seen in mutant p53. Two breast cancer cell lines, MCF7 and MDA-MB-231 are clinically distinct with varying molecular backgrounds as the first expresses wild type p53 and the latter expresses hyperactive, mutant p53. In order to determine which transcription regulatory factors are common and different between the two cell lines, purifications were carried out to isolate the Mediator complex from each of these two cell types. Further, to analyze the p53 network and p53-Mediator interactions, a different set of purifications were completed using nuclear extracts from both breast cancer cell types. Mass Spectrometry analysis of these samples identified proteins that are similar and different in the two distinct breast cancer cell lines. In future work, these differences will be explored to determine whether they might contribute to clinical differences, which include metastatic growth and drug resistance.