Identification of a sequence-specific single-stranded DNA binding protein that suppresses transcription of the mouse myelin basic protein gene.

The myelin basic protein (MBP) gene is expressed only in oligodendrocytes and Schwann cells, and expression follows a tightly regulated developmental time course. Cell type- and developmental stage-specific expression of the MBP gene appears to be regulated by a series of cis-acting elements located upstream of the transcription start site. The proximal element of the MBP regulatory region (MB1), located between nucleotides -14 and -50, is one of several elements participating in the programmed expression of MBP. In this report, we describe the molecular cloning and characterization of myelin gene expression factor-2 (Myef-2), a protein isolated from mouse brain that binds specifically to single-stranded DNA derived from the MB1 element and represses transcription of the MBP gene in transient transfection assay. Myef-2 mRNA is developmentally regulated in mouse brain; its peak expression occurs at postnatal day 7, prior to the onset of MBP expression. The developmental pattern of Myef-2 mRNA expression coincides with that previously described for SCIP, a POU domain transcription factor that also represses myelin basic protein expression. The myef-2 gene maps to mouse chromosome 2. The relevance of these findings for regulation of MBP gene expression and oligodendrocyte differentiation is discussed.