26S proteasome non-ATPase subunit 4 (PSMD4) that has a molecular weight of 41 kDa is included on chromosome 1 (1q21.3). PSMD4 protein is a subunit of the 19S regulatory region in the 26S proteasome. The proteasome breaks down proteins that are not needed or non-functional in the cell. We have limited data about the regulation of this gene in the literature. In our research, changes in the mRNA and protein levels of the PSMD4 gene were investigated in different cancer cell lines (prostate, breast, colon, cervix, hepatoma, osteosarcoma and pancreas) and a normal cell (human vein endothelial cell). The highest expression of PSMD4 gene was seen in HUVEC and PC-3 cells. Bioinformatic analysis was also performed on PSMD4 protein for different species namely human, mouse and rat. Our Bioinformatic analyses showed that first 250 nucleotides are much conserved in all three species.