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Dissertation/Thesis Abstract

Dissecting the Gene Regulatory Function of the MYC Oncogene with Single-Molecule Imaging
by Patange, Simona, Ph.D., University of Maryland, College Park, 2020, 134; 28023816
Abstract (Summary)

The MYC oncogene contributes to an estimated 100,000 cancer-related deaths annually in the United States and is associated with aggressive tumor progression and poor clinical outcome. MYC is a nuclear transcription factor that regulates a myriad of cellular activities and has direct interactions with hundreds of proteins, which has made a unified understanding of its function historically difficult.

In recent years, several groups have put forth a new hypothesis that questions the prevailing view of MYC as a gene-specific transcription factor and instead envision it as a global amplifier of gene expression. Instead of being an on/off switch for transcription, MYC is proposed to act as a `volume knob' to amplify and sustain the active gene expression program in a cell. The scope of the amplifier model remains controversial in part because studies of MYC largely consist of cell population-based measurements obtained at fixed timepoints, which makes distinguishing direct from indirect consequences on gene expression difficult. A high-temporal, high-spatial precision viewpoint of how MYC acts in single living cells does not exist.

To evaluate the competing hypotheses of MYC function, we developed a single-cell assay for precisely controlling MYC and interrogating the effects on transcription in living cells. We engineered `Pi-MYC,' an optogenetic variant of MYC that is biologically active, can be visualized under the microscope, and can be controlled with light. We combined Pi-MYC with single-molecule imaging methods to obtain the first real-time observations of how MYC affects RNA production and transcription factor mobility in single cells. We show that MYC increases the duration of active periods of genes population-wide, and globally affects the binding dynamics of core transcription factors involved in RNA Polymerase II transcription complex assembly and productive elongation. These findings provide living, single-cell evidence of MYC as a global amplifier of gene expression, and suggests the mechanism is by stabilizing the active period of a gene through interactions with core transcription machinery.

Indexing (document details)
Advisor: Girvan, Michelle, Larson, Daniel
Commitee: Sukharev, Sergei, Upadhyaya, Arpita, Dayie, Theodore Kwaku
School: University of Maryland, College Park
Department: Biophysics (BIPH)
School Location: United States -- Maryland
Source: DAI-B 82/3(E), Dissertation Abstracts International
Subjects: Biophysics, Cellular biology, Molecular biology
Keywords: Cancer, Microscopy, MYC, RNA, Single-molecule, Transcription
Publication Number: 28023816
ISBN: 9798678124388
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