STRUCTURAL ORGANIZATION AND CHROMOSOMAL MAPPING OF THE HUMAN ID-3 GENE

The helix-loop-helix (HLH) family of transcription factors plays a cen tral role in the regulation of cell growth, differentiation and tumour igenesis. Members of the Id (inhibitor of DNA binding) class of these nuclear proteins are able to heterodimerise with and thereby antagonis e the functions of other transcription factors of this family. We repo rt here on the genomic organisation of the human Id3 (HLH 1R21/heir1) gene. Comparison with the two other mammalian Id genes, Id1 and Id2, r eveals a highly conserved protein coding gene organisation consistent with evolution from a common, ancestral Id-like gene. In addition, by using a yeast artificial chromosome (YAC) clone of Id3, we have fine-s cale mapped the gene to chromosome band 1p36.1 by fluorescence in situ hybridisation (FISH) and, using the same FISH technique, we have dete cted heterogeneity in tumour-associated 1p36 chromosome translocations .