Polycomb repressive deubiquitinase (PR-DUB) is an enzyme that removes ubiquitin marks from histones. This enzyme is specifically involved in removing the H2AK119 ubiquitin mark on nucleosomes. This removal of the H2AK119 ubiquitin mark is essential for the proper function of the Polycomb repressive complex 1 (PRC1), which is a protein complex that is involved in gene silencing.

The PR-DUB enzyme is able to specifically remove the H2AK119 ubiquitin mark by using a unique mechanism. This mechanism involves the use of a zinc finger domain, which is a protein domain that is able to bind to specific DNA sequences. The PR-DUB enzyme uses its zinc finger domain to bind to the DNA sequence that surrounds the H2AK119 ubiquitin mark. This binding allows the PR-DUB enzyme to cleave the ubiquitin mark from the histone, thereby removing the mark and restoring the normal function of the PRC1 complex.

The specific removal of the H2AK119 ubiquitin mark by PR-DUB is essential for the proper function of the PRC1 complex. This complex is involved in gene silencing, and the removal of the H2AK119 ubiquitin mark allows the PRC1 complex to bind to and silence target genes. This is essential for the proper regulation of gene expression and the overall function of cells.