The Drosophila gene Posterior Sex Combs (Psc) encodes a ring-type zinc finger DNA binding protein (Polycomb group) involved in negative regulation of expression patterns of the antennapedia and bithorax homeotic selector gene complexes, and hence maintenance of segmental determination. Similar sequences have been identified in Homo sapiens and Mus musculus. Psc interacts genetically with z, brm, Sce, mxc, Asx, and several other genes. Mutations in Psc generate malformations of the longitudinal tracts. (from SWISS-PROT P35820, FlyBase 0005624, and NCI) [ ]