HJURP

HJURP, short for Holliday Junction Recognition Protein, is a eukaryotic centromere-associated histone chaperone that specifically deposits the histone variant CENP-A into centromeric chromatin. By loading CENP-A together with histone H4 onto centromeric DNA, HJURP helps establish and propagate the centromere identity needed for proper chromosome segregation during cell division.

In human cells, the deposition of new CENP-A at centromeres occurs primarily in late mitosis to early G1. HJURP is recruited to centromeres by the Mis18 complex (comprising Mis18α/β and M18BP1), and once localized, it binds CENP-A in complex with H4 to facilitate the assembly of CENP-A–containing nucleosomes. This chaperone activity protects CENP-A during deposition and contributes to the stability of centromeric chromatin, enabling correct kinetochore formation in subsequent divisions.

HJURP interacts with multiple centromere proteins and is considered essential for faithful chromosome segregation. Depletion or dysfunction of HJURP disrupts CENP-A localization, centromere integrity, and kinetochore function, leading to chromosome mis-segregation and aneuploidy.

Evolutionarily, HJURP is conserved across many eukaryotes, with functional homologs identified in different species; in budding yeast the related protein is known as Scm3. While the core role as a CENP-A chaperone is conserved, organism-specific variations exist in how the deposition machinery is organized.

The protein was named for its originally observed ability to recognize Holliday junction DNA, but its primary biological significance is as a CENP-A chaperone that maintains centromere identity through cell cycles.