Recruitment by the Repressor Freud-1 of Histone Deacetylase-Brg1 Chromatin Remodeling Complexes to Strengthen HTR1A Gene Repression

Abstract

Five-prime repressor element under dual repression binding protein-1 (Freud-1)/CC2D1A is genetically linked to intellectual disability and implicated in neuronal development. Freud-1 represses the serotonin-1A (5-HT1A) receptor gene HTR1A by histone deacetylase (HDAC)-dependent or HDAC-independent mechanisms in 5-HT1A-negative (e.g., HEK-293) or 5-HT1A-expressing cells (SK-N-SH), respectively. To identify the underlying mechanisms, Freud-1-associated proteins were affinity-purified from HEK-293 nuclear extracts and members of the Brg1/SMARCCA chromatin remodeling and Sin3A-HDAC corepressor complexes were identified. Pull-down assays using recombinant proteins showed that Freud-1 interacts directly with the Brg1 carboxyl-terminal domain; interaction with Brg1 required the carboxyl-terminal of Freud-1. Freud-1 complexes in HEK-293 and SK-N-SH cells differed, with low levels of BAF170/SMARCC2 and BAF57/SMARCE1 in HEK-293 cells and low-undetectable BAF155/SMARCC1, Sin3A, and HDAC1/2 in SK-N-SH cells. Similarly, by quantitative chromatin immunoprecipitation, Brg1-BAF170/57 and Sin3A-HDAC complexes were observed at the HTR1A promoter in HEK-293 cells, whereas in SK-N-SH cells, Sin3A-HDAC proteins were not detected. Quantifying 5-HT1A receptor mRNA levels in cells treated with siRNA to Freud-1, Brg1, or both RNAs addressed the functional role of the Freud-1-Brg1 complex. In HEK-293 cells, 5-HT1A receptor mRNA levels were increased only when both Freud-1 and Brg1 were depleted, but in SK-N-SH cells, depletion of either protein upregulated 5-HT1A receptor RNA. Thus, recruitment by Freud-1 of Brg1, BAF155, and Sin3A-HDAC complexes appears to strengthen repression of the HTR1A gene to prevent its expression inappropriate cell types, while recruitment of the Brg1-BAF170/57 complex is permissive to 5-HT1A receptor expression. Alterations in Freud-1-Brg1 interactions in mutants associated with intellectual disability could impair gene repression leading to altered neuronal development.

Neuroepigenetic signatures of age and sex in the living human brain

“…For example, in vivo expression of the serotonin receptor (5-HTR 1A ) is increased in the hippocampus and amygdala of females compared to males in humans 61,62 . Transcription of 5-HTR 1A mRNA is regulated in part by HDAC1/2 63 , which suggests that altered HDAC levels could affect neurotransmitter systems. Additionally, serotonin-dependent activation of the serotonin receptor (5-HTR 2A ) inhibits HDAC2 promoter activity in human cells 64 , while 5-HTR 2A inhibition increases Hdac2 transcription and negatively affects synaptic remodeling and cognitive behavior through NF-κB signaling in rodents 65 , which may have relevance to depression and other neuropsychiatric disorders.…”

Genetic, epigenetic and posttranscriptional mechanisms for treatment of major depression: the 5-HT1A receptor gene as a paradigm

“…168,169 In particular, the repressor Freud-1 assembles different BRG1 chromatin remodelling complexes in non-neuronal versus neuronal cells to mediate HDAC-dependent and -independent repression, respectively. Neuronal cells show de-repression of the HTR1A gene upon depletion of Freud-1 or BRG1, while non-neuronal cells are resistant, 169,170 reflecting silencing of 5-HT 1A receptor expression in the latter. This reversible regu lation of 5-HT 1A receptor expression in neurons may account for the dynamic regulation of 5-HT 1A autoreceptors by Freud-1 in vivo.…”

CaMKIV-Mediated Phosphorylation Inactivates Freud-1/CC2D1A Repression for Calcium-Dependent 5-HT1A Receptor Gene Induction

“…As a repressor, Freud-1 recruits several different transcriptional regulators including the SWI/SNF chromatin remodeling complex, Brg1-BAF170/57, and corepressor complex, Sin3A-HDAC1/2, the latter being absent in SK-N-SH cells compared to HEK-293 cells [ 45 ]. Thus, the Freud-1-mediated repression was blocked by the HDAC inhibitor, trichostatin, in HEK-293 cells but not in SK-N-SH cells, indicating HDAC-independent repression [ 31 ].…”