The members of the mortality factor family include mortality factor 4 (MORF4), MORF4L1 (also known as MRG15) and MORF4-related gene X (MRGX). The human MORF4 gene maps to chromosome 4q33-q34.1. MORF4 induces a senescent-like phenotype in complementation group B immortal cell lines. MORF4 family-associated protein 1 (MRFAP1), also known as GAM14 or PGR1, is a 127 amino acid member of the MORF4 family-associated protein family. Localized to nucleus and cytoplasm, MRFAP1 colocalizes with MORF4L1 to the cell nuclei. Its association with MORF4L1 and Rb1 suggests that MRFAP1 may play a role in transcription regulation. The gene encoding human MRFAP1 maps to chromosome 4p16.1.