GOLPH3 (golgi phosphoprotein 3), also known as GOPP1, GPP34 or MIDAS, is a 298 amino acid protein that localizes to both the cytoplasm and the Golgi stack membrane where it is thought to play a regulatory role in protein trafficking within the Golgi. GOLPH3 is subject to post-translational phosphorylation and is encoded by a gene which maps to human chromosome 5. Chromosome 5 contains 181 million base pairs and comprises nearly 6% of the human genome. Chromosome 5 is associated with Cockayne syndrome through the ERCC8 gene and familial adenomatous polyposis through the adenomatous polyposis coli (APC) tumor suppressor gene. Treacher Collins syndrome is also chromosome 5-associated and is caused by insertions or deletions within the TCOF1 gene. Deletion of the p arm of chromosome 5 leads to Cri du chat syndrome, while deletion of the q arm or of chromosome 5 altogether is common in therapy-related acute myelogenous leukemias and myelodysplastic syndrome.