Protein tyrosine phosphatase which stimulates progression from G1 into S phase during mitosis. Promotes tumors. Inhibits geranylgeranyl transferase type II activity by blocking the association between RABGGTA and RABGGTB. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Inhibited by sodium orthovanadate and pentamidine. In contrast to PTP4A1 and PTP4A3, does not interact with tubulin. Interacts with RABGGTB. Ubiquitously expressed, with highest levels in skeletal muscle, heart and thymus. Overexpressed in prostate tumor tissue. Farnesylated. Farnesylation is required for membrane targeting and for interaction with RABGGTB. Unfarnesylated forms are redirected to the nucleus and cytosol. A processed pseudogene with 96% sequence identity was found in the BRCA1 (113705) region of 17q21. Belongs to the protein-tyrosine phosphatase family.