The RING finger domain occurs in a wide variety of proteins involved in cellular regulation. The polymerase chain reaction was used to search for novel RING finger proteins, using primers derived from expressed sequence tags (ests). A cDNA encoding a novel RING linger protein expressed in brain, lung, breast, placenta, kidney, muscle, and germinal center B cells is described. The human gene is expressed in a variety of tumors, including anaplastic oligodendroglioma and maps to chromosome 10q24.3, a region showing frequent deletion or loss of heterozygosity in glioblastomas. It was therefore designated glioblastoma expressed RING finger protein (GERP). GERP contains an N-terminal RING finger, followed by two B-boxes and a coiled-coil, and thus belongs to the RBCC subfamily of RING finger proteins. The structure of this protein and its mapping to a locus thought to harbor tumor suppressor genes indicates that it may be a new tumor suppressor gene important in gliomas and other malignancies.