A new Cys2/His2 zinc finger gene, rKr2, is expressed in differentiated rat oligodendrocytes and encodes a protein with a functional repressor domain.

The function of the vertebrate nervous system is dependent on the proper myelination of its fiber tracts. Myelin of the CNS is produced by oligodendrocytes. To identify gene regulatory proteins expressed in this particular glial cell type, we isolated cDNAs coding for Cys2/His2 zinc finger proteins from a rat oligodendrocyte cDNA library. One clone, named rKr2 (rKr for rat Krüppel-type protein), encodes a protein with 19 carboxy-terminal zinc finger domains and an amino-terminal Krüppel-associated box domain. This amino-terminal domain of the rKr2 protein behaved as a strong transcriptional repressor module when fused to the DNA binding domain of yeast GAL4 and tested on an appropriate reporter construct. High levels of rKr2 mRNA in adult rat tissues were found only in the CNS and testis; in the CNS, the message was predominantly expressed in differentiated oligodendrocytes. The modular structure of the rKr2 protein (carboxy-terminal DNA binding domain, amino-terminal repressor module) and its expression pattern suggest that it acts as a sequence-specific transcriptional repressor in the myelin-producing glial cells of the CNS.