This family consists of Pirin proteins from both eukaryotes and prokaryotes. The function of Pirin is unknown but the gene coding for this protein is known to be expressed in all tissues in the human body although it is expressed most strongly in the liver and heart. Pirin is known to be a nuclear protein, exclusively localized within the nucleoplasma and predominantly concentrated within dot-like subnuclear structures. A tomato homolog of human Pirin has been found to be induced during programmed cell death. Human Pirin interacts with Bcl-3 and NFI and hence is probably involved in the regulation of DNA transcription and replication. It appears to be an Fe(II)-containing member of the Cupin superfamily.