Dominant-Negative Mutants of Helix-Loop-Helix Proteins: Transcriptional Inhibition

Abstract

This chapter reviews the basic helix-loop-helix (B-HLH) family of transcription factors that binds to sequence-specific DNA as homo- or heterodimers to modulate gene expression. B-HLH proteins have been found in all eukaryotic systems examined with over 125 members in the human genome. B-HLH proteins regulate the expression of genes involved in cell growth and differentiation of a variety of cell types, including muscle, heart, blood, nerve, and sex determination. The chapter explains two general methods used to determine the biological function of a gene. The first is to mutate the gene, either by changing the DNA sequence by classical mutagenesis or by deleting the gene directly. The gene deleted from the germ line, resulting in a gene “knockout,” or from a particular tissue using the Cre/Lox system. The second method, instead of altering the gene or deleting a gene, inhibits its activity. A variety of techniques can be used to achieve such inhibition. These include binding novel transcription factors to the promoter region of a gene to suppress its expression, using RNAi-based strategies to inactivate mRNA function, or using protein-based strategies that function by inactivating the protein product of a gene.