TOM1 genes map to human chromosome 22q13.1 and mouse chromosome 8C1 and encode proteins similar to the endosomal proteins HGS and STAM.

The avian tom1 (target of myb 1) gene has been previously characterized from v-myb-transformed cells. We report here cloning of the human and mouse tom1 orthologs. Both genes are expressed ubiquitously, with the highest levels in skeletal muscle, brain, and intestines, as assessed by Northern blot and mRNA in situ hybridization. The N-terminal domain of the TOM1 protein shares similarity with HGS (hepatocyte growth factor-regulated tyrosine kinase substrate) and STAM (signal-transducing adaptor molecule), which are associated with vesicular trafficking at the endosome. A putative coiled-coil domain was also detected in the central part of the TOM1 protein. This domain structure suggests that TOM1 is another member of a family of genes implicated in the trafficking regulation of growth-factor-receptor complexes that are destined for degradation in the lysosome. We also show that a human paralog of TOM1 (TOM1-like gene 1) exists. Furthermore, we provide a transcription map over a 190-kb contig of the TOM1 region. This map includes its distal neighbors HMOX1 and MCM5 and two proximal novel genes, one of which is a HMG-box-containing gene (HMG2L1), and the other of unknown function. Using a genomic PAC clone, we demonstrate that the mouse Tom1 and Hmox1 genes are part of an as yet undescribed syntenic group between mouse chromosome 8C1 and human chromosome 22q13.1.