ABSTRACT
The transcription factor NFκB regulates the B-cell-specific expression of the immunoglobulin κ light-chain gene. Immunoglobulin κ gene expression is activated when pre-B cells differentiate into mature B lymphocytes which produce immunoglobulin. The activation of a specific transcription factor, such as NFκB, from a preexisting inactive form can play a role in cell type-specific gene expression as well as in the activation of gene expression in response to specific cellular signals. MyoD represents a transcription factor that is controlled at the level of its synthesis, with such regulation playing a key role in muscle cell differentiation. A similar conversion of MEF2 to a transcriptional repressor is observed when the protein is modified by addition of the small protein small ubiquitin-related modifier, whereas acetylation of MEF2 promotes its ability to act as a transcriptional activator. The MEF2 genes contain a specific exon known as β, which encodes an additional transcriptional activation domain.
