Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Biochemistry

First Advisor

Dr. Thomas R. Cech

Abstract

Polycomb Repressive Complex 2 (PRC2) is a histone methyltransferase that specifically deposits mono-, di-, and tri-methylation marks onto chromatin. This activity triggers epigenetic silencing, a process critical for cell differentiation and maintenance of cellular identity. In mammalian cells, how PRC2 is recruited to target sites is unknown, but it is speculated that RNA, histone modifications, nucleosome architecture, and DNA elements all possess direct or indirect recruitment and regulatory roles. However, the relative binding affinity of PRC2 for these diverse biological substrates remains poorly understood. In the present study, the binding affinity of PRC2 for various RNAs and nucleosomes were tested using bulk biochemical and single-molecule approaches using purified recombinant human PRC2 complex. In addition, the effect on PRC2’s association with nucleosomes in the presence of RNA was tested. Binding experiments revealed that PRC2 reads consecutive guanines in RNAs, and that RNA sequences with the propensity to form G-quadruplex structures are ideal ligands. This study tests PRC2 interaction with nucleosomes. Intriguingly, PRC2-nucleosome associations are affected in the presence of competitor RNA. Collectively, findings from this work offer new insights into the mechanistic details of PRC2 recruitment.