Imaging Transcription Dynamics in Single Cancer Cells

Abstract

Over 50% of cancer patients harbor a mutation in the tumor suppressor protein p53. In healthy cells during stress, p53 recognizes specific genomic response elements (REs) to induce expression of stress response genes involved in cell cycle arrest, apoptosis and DNA damage. To maintain genomic stability, expression of these tumor suppression genes must be rapidly turned on and off. It is currently poorly understood how p53 spatiotemporally regulates expression of target genes in the complex milleu of the nucleus and how this process goes awry in cancer cells.To better mechanistically decipher changes in stress response gene expression in cancer cells, we established a single molecule imaging system that allows us simultaneously to track p53 and RNA Polymerase II binding along with transcription dynamics in single live cells. Single particle tracking studies indicate a dynamic interaction between p53 and chromatin that varies in distinct sub-nuclear compartments. Live cell monitoring of gene expression from a p53 target gene reveals dynamic bursts of transcription in discrete sub-nuclear regions. Modulation of wild-type p53 levels leads to changes in the transcription burst frequency and intensity. Introduction of cancer associated mutant p53 into cells leads to changes in both p53 sub-nuclear localization and transcription bursting dynamics. Future studies will focus on how chromatin structure dynamically regulates sub-nuclear localization and expression of p53 targets genes. This work is supported in parts via the 4D Nucleome consortia NIH grant 1U01EB021236-01.