Hes2 encodes a mammalian basic helix-loop-helix transcriptional repressor 
homologous to the products of Drosophila hairy and Enhancer of split. Here, we 
isolated and characterized the mouse Hes2 gene. This gene consists of four 
exons, and all the introns are located within the protein-coding region at 
positions homologous to those of other Hes genes. On the inter-specific 
backcross analyses, mouse Hes2 is mapped to the distal region of Chromosome 4 
near the Hes3 and Hes5 loci, which are different from the Hes1 locus on 
Chromosome 16. Upstream of the transcription initiation site, there are GC-rich 
regions, but a typical TATA box is not present. Transient transfection analyses 
demonstrated that, while Hes1 and Hes5 promoter activities are significantly 
upregulated by the active form of Notch, a key regulator of cellular 
differentiation, Hes2 and Hes3 promoter activities are not. These results 
suggest that Hes genes are functionally classified into two groups: those that 
are regulated by Notch and those that are not.