The PWWP domain is an essential part of the cytokine-like nuclear factor n-pac protein, or NP60, which enhances the activity of MAP2K4 and MAP2K6 kinases to phosphorylate p38-alpha. In a variety of cell lines, NP60 has been shown to localize to the nucleus. In addition to the PWWP domain, NP60 also contains an AT-hook and a C-terminal NAD-binding 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.