PCNP (PEST proteolytic signal containing nuclear protein) is a nuclear protein implied to play a role in cell cycle regulation and tumorigenesis. This protein is ubiquitinated post-translationally by NIRF, an ubiquitin ligase. PCNP exsists as three isoforms produced by alternative splicing events and may be involved in cell cycle regulation. Recombinant human PCNP protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.