ABSTRACT
Several genes encoding proteins critical to the neuronal phenotype, such as the brain type II sodium channel gene, are expressed to high levels only in neurons. This cell specificity is due, in part, to long-term repression in nonneural cells mediated by the repressor protein REST/NRSF (RE1 silencing transcription factor/neural-restrictive silencing factor). We show here that CoREST, a newly identified human protein, functions as a corepressor for REST. A single zinc finger motif in REST is required for CoREST interaction. Mutations of the motif that disrupt binding also abrogate repression. When fused to a Gal4 DNA-binding domain, CoREST functions as a repressor. CoREST is present in cell lines that express REST, and the proteins are found in the same immunocomplex. CoREST contains two SANT (SW13/ADA2/NCoR/TFIIIB B) domains, a structural feature of the nuclear receptor and silencing mediator for retinoid and thyroid human receptors (SMRT)-extended corepressors that mediate inducible repression by steroid hormone receptors. Together, REST and CoREST mediate repression of the type II sodium channel promoter in nonneural cells, and the REST/CoREST complex may mediate long-term repression essential to maintenance of cell identity.
Subject(s)
DNA-Binding Proteins/physiology , Gene Expression Regulation , Nerve Tissue Proteins/physiology , Repressor Proteins/physiology , Transcription Factors , Zinc Fingers , Amino Acid Sequence , Animals , Cells, Cultured , Co-Repressor Proteins , Humans , Molecular Sequence Data , Nerve Tissue Proteins/chemistry , Nerve Tissue Proteins/genetics , Neurons/physiology , Rabbits , Repressor Proteins/chemistry , Repressor Proteins/genetics , TransfectionABSTRACT
The type II voltage-dependent sodium channel is present in neuronal cells, where it mediates the propagation of nerve impulses. Restricted expression of the type II sodium channel gene to neurons is due, at least in part, to binding of the repressor protein REST (also termed NRSF or XBR) to the RE1 (also called NRSE) sequence in the type II sodium channel gene. Previous studies have shown that a domain in REST containing eight GL1-Krüppel zinc finger motifs mediates DNA binding. Deletional and GAL4-fusion gene analyses now reveal repressor domains that lie outside of the DNA-binding domain in both the amino and carboxyl termini of REST. Mutational analysis further identifies a single zinc finger motif in the carboxyl-terminal domain as being essential for repressing type II sodium channel reporter genes. These studies reveal two domains in REST that may mediate interactions with other proteins involved in restricting expression of a large set of genes to the vertebrate nervous system.
