The tumor suppressor gene MEN1 and several oncogenes including CCND1/cyclin D1/PRAD1 map to chromosome 11q13. However, molecular and cytogenetic analysis suggests the presence of a second tumor suppressor locus at this chromosome region. We have identified a novel gene from chromosome 11q13, which encodes a protein of 126 amino acids sharing an overall 57% identity with the p12(DOC-1) protein encoded by the DOC-1 gene, the human homolog of hamster putative tumor suppressor doc-1 (deleted in oral cancer-1). We therefore designated the novel gene as DOC-1R for DOC-1-related. The cytogenetic location was confirmed by chromosome fluorescent in situ hybridization. Northern blot analysis indicated that it was expressed in all the tissues examined. DOC-1R protein showed heterogeneous subcellular localization. RT-PCR-SSCP analysis failed to detect deleterious mutations of the DOC-1R transcript in four premalignant oral keratinocyte lines and 20 different cancer cell lines from tumor types which frequently harbor LOH at chromosome 11q13.