Identification of a strand-specific Egr response element binding complex enriched in rat brain.

Abstract

Multiple members of the Egr family of transcription regulatory factors are rapidly induced in response to neuronal stimulation and share a common double-stranded DNA binding consensus sequence, referred to as the Egr response element. Recent studies have identified transcription regulatory factors that bind preferentially to short segments of single-stranded DNA, rather than the conventional double-stranded versions of regulatory elements. Accordingly, in the present study, we have investigated whether the Egr response element may also be regulated by trans factors that bind to single-stranded versions of this cis element. Using gel-shift studies, we have identified a protein complex that binds selectively to the G-rich strand of the Egr response element. In competition studies, an RNA oligonucleotide containing the corresponding G-rich sequence is approximately 25-fold less potent than its DNA counterpart. This DNA binding complex, referred to as GS1, is present in several regions of the rat brain with highest levels in cerebellum; negligible binding activity was detected in multiple peripheral tissues surveyed. UV cross-linking studies revealed two major protein bands with estimated molecular masses of 36 and 30 kDa. The highly restricted tissue distribution of this complex and its sequence-specific binding properties indicate that GS1 may be involved in regulating transcription directed by the Egr response element in brain.