MYEF-3, A DEVELOPMENTALLY CONTROLLED BRAIN-DERIVED NUCLEAR-PROTEIN WHICH SPECIFICALLY INTERACTS WITH MYELIN BASIC-PROTEIN PROXIMAL REGULATORY SEQUENCES

Myelin basic protein (MBP) gene contains the upstream regulatory seque nce that confers cell type-and stage-specific transcription to MBP exp ression in oligodendrocytes during brain development. The MB1 regulato ry motif located between -14 to -50 with respect to transcription star t site binds to a brain derived nuclear protein and plays an important role in transcriptional activation of the MBP promoter in transfectio n assay. Here, we report the isolation of a recombinant cDNA clone, te rmed myelin expression factor-3, (MyEF-3) from a mouse brain expressio n library that encodes a novel protein which interacts with the MBP MB 1 domain. Computer assisted evaluations of the MyEF-3 sequence reveale d several interesting features including four sites for phosphorylatio n by casein kinase II, a transmembrane domain at the N-terminus, a nuc lear localization signal and a Zinc finger domain at the carboxyl term inal. Results from Western and band shift assays indicate that MyEF-3 binds efficiently to double-stranded MB1 as well as the single-strande d non-coding strand of MB1. The use of short DNA fragments encompassin g the nucleotide base substitutions across the MB1 domain in competiti on band shift assay revealed that the ten nucleotide sequence, 5'-GCCT GTCTTT-3' is important for binding of MyEF-3 to DNA. Results from Nort hern blot studies demonstrate that expression of MyEF-3 is restricted to brain and developmentally regulated during brain maturation. The bi ological importance of MyEF-3 in the cell type-and stage-specific expr ession of MBP during brain development is discussed. (C) 1998 Academic Press.