CBX4(Chromobox 4) also known as NBP16 is a member of the Polycomb group (PcG) proteins, which are crucial for gene silencing and regulation of Hox genes through chromatin structure modification during transcription. Located on human chromosome 17q25.3, CBX4 interacts with other PcG proteins, such as CBX8, and shares structural similarities with M33, binding to PcG protein RING1 via a conserved c-box motif found in the C-terminus of RING1. CBX4 functions as a transcriptional repressor of proto-oncogenes, and disruption in CBX4 activity can lead to proto-oncogene transcription upregulation, potentially resulting in cellular transformation. CBX4 acts as a long-range transcriptional silencer, which is vital for maintaining proper gene expression patterns.