The individual's embryogenesis, cellular proliferation and differentiation are precisely regulated by various kinds of genes in a time-dependent manner. PcG family is a group of the most important genes that related to system development. HPC2 protein which is encoded by a critical PcG gene, hpc2, associates with other PcG proteins, such as HPH, BMI-1 as well as RING1 and constitutes HPC/HPH PcG complex to maintain the repressed state of homeotic gene, so that it can regulate the body development, cellular proliferation and directional differentiation. Furthermore, HPC2 has also been found to interact with some other proteins, suggesting that HPC2 may possess some other functions. Therefore, further study of hpc2 is not only helpful to the understanding of the mechanism of biological action of PcG proteins and expanding of the knowledge on the regulation of gene expression, but also beneficial to the discovery of potential relationship between PcG family and other signal transduction pathways for better understanding of the cellular signal transduction network.