UC San Diego

The neuron-restrictive silencer factor (NRSF), also known as repressor element -1 (RE1) silencing transcription factor (REST), is known to act as a transcriptional repressor of neuron-specific genes in nuclei of non- neuronal cells. REST binds a DNA sequence known as neuron- restrictive silencer elements (NRSEs/RE1s) and recruits co -repressors to carry out silencing chromatin modifications. Recent REST ChIP-seq publications have shown that REST binding is not limited to the canonical RE1 sequence, but binds multiple variations of it across the genome. This study focuses on determining REST's capacity to act as a repressor based on the binding site's degree of correspondence to the canonical RE1 motif. I show that the RE1 right half site acts as a REST- recruiting repressive element. I have also begun studying differential recruitment of REST protein and its cofactors between human embryonic stem cells (hESCs) and hESC- derived neural progenitor cells (NPCs) on a genome-wide scale using chromatin immunoprecipitation followed by massive parallel sequencing of DNA tags (ChIP-seq). I also present preliminary data suggesting that REST may have a second function as a post-transcriptional activator. Increased luciferase expression is observed when reporter constructs were cotransfected with high levels of REST in mouse Neuro2A (N2A) cells. I show that this concentration dependent function of REST is due to the cell's limited capacity to transport and/or retain REST in the nucleus, where it acts as a repressor. With increasing concentrations of REST, a large fraction remains in the cytoplasm, where REST may bind and stabilize the luciferase transcript and/or enhance its translation