The PWWP domain was first identified in the WHSC1 (Wolf-Hirschhorn syndrome candidate 1) protein, a protein implicated in Wolf-Hirschhorn syndrome (WHS). When translocated, WHSC1 plays a role in lymphoid multiple myeloma (MM) disease, also known as plasmacytoma. WHCS1 proteins typically contain two copies of the PWWP domain. The PWWP domain, named for a conserved Pro-Trp-Trp-Pro motif, is a small domain consisting of 100-150 amino acids. The PWWP domain is found in numerous proteins that are involved in cell division, growth and differentiation. Most PWWP-domain proteins seem to be nuclear, often DNA-binding, proteins that function as transcription factors regulating a variety of developmental processes.