BMB Section Seminar: "Chromatin dynamics during transcription initiation at single gene loci"

Prof. Kerstin Bystricky Laboratory for Eucaryotic Molecular Biology (LBME), University of Toulouse, CNRS, Toulouse, France  

Kerstin Bystricky. Photo: Private.

The spatial organization of chromatin in the nucleus is non-random and chromatin dynamics participate in regulating nuclear processes from gene expression to DNA repair. Transcriptional activity has been correlated with relocalisation of gene loci within the cell nucleus. However, we do not know whether changes in transcription per se alter motion of the underlying chromatin fiber.

We use estrogen inducible loci in human mammary tumour cells as a model system in which chromatin remodelling via looping allows priming of the gene environment for transcription activation. We mapped chromatin folding over several hundred kb around estrogen responsive genes using 3D DNA and RNA FISH and confronted these measurements with 5C data to establish models of domain organization which are cell type specific. Our results indicate that rapid estradiol induction of gene expression occurs in the context of pre-existing chromosomal architectures that become stabilized in response to estradiol signalling. Using the non-invasive ANCHOR method to label DNA for imaging chromatin in living human cells, we follow chromatin dynamics of a specific gene locus during the first 30 minutes of transcription activation. Simultaneous observation of mobility and transcription of a single, hormone-responsive gene, CyclinD1 showed high cell-to-cell variability. Addition of estradiol caused a rapid decline in chromatin motion. Our observation that transcription initiation locally reduces chromatin dynamics within minutes is compatible with the idea that existing chromatin conformation reorganizes to facilitate enhancer promoter contacts and chromatin de- and reassembly.

Example of a double tagged human MCF7 cell, spinning disk confocal image.

Unpublished: I Goiffon, Bystricky group, LBME Toulouse


Ragnhild Eskeland
Published Dec. 30, 2016 12:38 PM - Last modified Jan. 2, 2017 1:14 PM