Chromatin Immunoprecipitation Techniques in Neuropsychiatric Research

B2 SINE RNA as a novel regulator of glucocorticoid receptor transcriptional activity

Glucocorticoids are a key component to the cellular response to stress. Glucocorticoids act via glucocorticoid receptors found ubiquitously in the brain and body. Glucocorticoid receptors can bind to response elements throughout the genome to elicit changes in transcription, an adaptation observed at the cellular level. Yet, the transcriptional changes as a consequence of glucocorticoid receptor activation are variable across brain regions, stress conditions and recurrent bouts of glucocorticoid exposure. Here we describe a non-coding RNA, B2 SINE, which is regulated by glucocorticoids and can in turn regulate glucocorticoid receptor transcriptional activity. We show that activated glucocorticoid receptors interact directly with B2 SINE RNA via a decoy response element contained within the transcript sequence and alter receptor binding to response elements in the genome and, subsequently, changes in loci expression.

Corticosterone dynamically regulates retrotransposable element expression in the rat hippocampus and C6 cells

The hippocampus is a highly plastic brain region sensitive to environmental stress. It shows dynamic changes in epigenetic marks associated with stress related learning. Previous work has shown that acute stress induces substantial transient changes in histone H3 lysine 9 trimethylation (H3K9me3). Moreover, increased H3K9me3 is enriched in hippocampal gene deserts accumulating within endogenous retroviruses and transposable elements. We have found that in response to acute glucocorticoid treatment, a similar change in global H3K9me3 is observed. However, when localized we found that H3K9me3 is markedly decreased at B2 short interspersed nuclear elements but not within intracisternal-A particle endogenous retroviruses. Further, decreased H3K9me3 valence within B2 elements was associated with increased transcript abundance. These data demonstrate the capacity for acute glucocorticoids to mobilize transposable elements via epigenetic unmasking. Reconciled with previous findings following acute stress, this suggests the capacity for mobile elements to potentially function as novel regulators given their dynamic regulation by stress and glucocorticoids.