Transcriptional Activation of a Constitutive Heterochromatic Domain of the Human Genome in Response to Heat Shock

Abstract

Heat shock triggers the assembly of nuclear stress bodies that contain heat shock factor 1 and a subset of RNA processing factors. These structures are formed on the pericentromeric heterochromatic regions of specific human chromosomes, among which chromosome 9. In this article we show that these heterochromatic domains are characterized by an epigenetic status typical of euchromatic regions. Similarly to transcriptionally competent portions of the genome, stress bodies are, in fact, enriched in acetylated histone H4. Acetylation peaks at 6 h of recovery from heat shock. Moreover, heterochromatin markers, such as HP1 and histone H3 methylated on lysine 9, are excluded from these nuclear districts. In addition, heat shock triggers the transient accumulation of RNA molecules, heterogeneous in size, containing the subclass of satellite III sequences found in the pericentromeric heterochromatin of chromosome 9. This is the first report of a transcriptional activation of a constitutive heterochromatic portion of the genome in response to stress stimuli.

Global analysis of DNA methylation and transcription of human repetitive sequences.

“…In agreement with previous reports, 19,20,41,42 we found an upregulation of pericentromeric satellites transcription upon thermal stress (Fig. 5A and Suppl.…”

“…Indeed, the RepArray analysis of the RNA profile of repeats in Hela cells upon thermal stress is consistent with previous works reporting transcriptional activation of pericentromeric satellite repeats upon heat shock. 19,41 Interestingly, we also detected a weak expression of several other repeats suggesting that transcriptional reprogramming of DNA repeats in response to stress is not limited to pericentromeric satellites but also concerns other repeat classes such as telomeric satellites, SINEs retroelements and DNA transposons. Our repeatexpression profiling using microarray-based approach provides thus further insight into the transcriptional reprogramming induced in response to thermal stress.…”

Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts

“…A new period began when several groups independently demonstrated transcription of the satellite DNA under stress conditions. 71,72 These examples removed any questions regarding satellite DNA complete transcriptional inactivity.…”

Pericentric and centromeric transcription: a perfect balance required

“…The first indication of the functional importance of satellite transcripts was the discovery that transcription of certain pericentric satellites was induced under cellular stress in human cells (Jolly et al 2004;Rizzi et al 2004). Stress can be induced in cells by exposing them to any condition outside of their optimal growth range; this includes subjecting cells to high temperature (heat shock), heavy metals, hazardous chemicals, ultraviolet radiation, and hyperosmotic or oxidative conditions (Valgardsdottir et al 2008).…”