Graduation Date

5-2019

Document Type

Master's Thesis

Degree

Master of Science

Program

Biological Science

Program Director

Meredith Protas, PhD

First Reader

Christopher Benz, PhD

Second Reader

Ekaterina Kalashnikova, PhD

Abstract

Histone deacetylase inhibitors (HDACi) are a novel class of drugs that target histone deacetylases, enzymes that by removing acetyl groups from the lysine resides of histones and many other non-histone proteins alter the cell’s chromatin structure and cellular functions, including regulation of protein translation and transcript stability. The mechanism of how these inhibitors destabilize some but not all transcripts remains incompletely understood. Our recent research has demonstrated that treatment of ERBB2-positive breast cancer cells with the HDAC1/2 selective HDACi, FK228 (Romidepsin) promotes rapid decay of various oncogenic mRNA transcripts including ERBB2 mRNA. Most recently we have demonstrated that histone acetyltransferase p300 (p300 HAT) appears to maintain the stability of ERBB2 mRNA and its knock-down by siRNA enhances ERBB2 mRNA decay without affecting housekeeping gene transcripts like GAPDH mRNA. As with FK228 treatment, the potent p300 HAT inhibitor, A-485, comparably induces ERBB2 mRNA decay within hours of cell exposure. Given these findings, we now propose that FK228 and A-485 destabilize ERBB2 mRNA by modulating the posttranslational acetylation of p300 HAT and known or unknown p300 HAT substrates. To test this hypothesis we employed mass spectrometry to detect intracellular p300 HAT acetylation, along with that of other p300-associated proteins, and measured ERBB2 transcript decay by RT-PCR following FK228 and A-485 treatment and compared to siRNA knockdown of p300. Our findings support a new mechanistic model of ERBB2 transcript stability based on p300 and its acetylation status. We also propose that FK228 and A-485 offer two new drug treatment approaches for patients with ERBB2-positive breast cancers refractory to current anti-ERBB2 therapeutics, targeting the activation of our newly identified ERBB2 transcript destabilizing mechanism.

Available for download on Saturday, May 14, 2022

Share

COinS