ABERRANT EXPRESSION OF HIGH-MOBILITY GROUP CHROMOSOMAL PROTEIN-14 AFFECTS CELLULAR-DIFFERENTIATION

High mobility group (HMG) 14 is a ubiquitous chromosomal protein that binds specifically to nucleosomal DNA and may be involved in a process that confers distinct properties to the chromatin structure of transc riptionally active genes. To explore the involvement of this protein i n regulation of gene expression, we studied the effect of aberrant exp ression of HMG-14 protein on cellular differentiation. We produced sta bly transfected C2C12 mouse myoblasts expressing the human HMG-14 prot ein under the control of the mouse mammary tumor virus promoter. Trans formed colonies retained their potential do differentiate into myotube s. Induction of human HMG-14 expression by dexamethasone inhibited the myogenic process. Revertant colonies, which lost the ability to expre ss human HMG-14, regained the ability to differentiate into myotubes. Inhibition of myoblast differentiation by aberrantly expressed HMG-14 correlated with down-regulation of myogenic determination factors. The results suggest that proper cellular differentiation requires regulat ed expression of HMG-14 protein and are consistent with the possibilit y that this protein may be involved in gene regulation.