The neuronal identifier element is a cis-acting positive regulator of gene expression.

A middle-repetitive DNA element termed the identifier (ID) sequence, located in introns of postnatal-onset neuronal-specific genes, is transcribed in early postnatal rats by RNA polymerase III (Pol III) specifically in the brain. We show that these Pol III transcripts, although brain specific in vivo, are also expressed in immortalized rodent cell lines in culture. We demonstrate that the ID sequence can act as a positive regulator or enhancer of RNA polymerase II gene expression in cell lines that express these RNAs but not in primary cells in which Pol III transcription of the ID sequence is absent. Thus, ID elements may be positive regulators of postnatal-onset neuronal-specific gene expression.