PDS5, a cohesion protein, is important for proper chromosome segregation in lower organisms and has two homologs in vertebrates (PDS5A and PDS5B). The precocious dissociation of sisters 5A (Pds5A), also known as sister chromatid cohesion protein 112 is a nuclear protein, expressed from the S right through to the mitotic phase. It is highly conserved from yeast to man and plays a role in the establishment, maintenance, and dissolution of sister chromatid cohesion. The mutation of Pds5A orthologs in lower organisms results in chromosome missegregation, aneuploidy, and DNA repair defects. It is considered that such defects can cause either cell death or contribute to the development of cancer cells. Indeed, altered expression levels of Pds5A have been observed in tumors of the breast, kidney, esophagus, stomach, liver, and colon.