This entry represents a central, conserved region found in Holliday junction recognition protein from humans (HJURP) and similar proteins from vertebrates. This domain is not present in Holliday junction recognition proteins from fungi. However, both the N-terminal domain and a repeated domain that appears further downstream, also of unknown function, appear in all both vertebral and fungal Holliday junction recognition proteins. HJURP is a conserved non-histone protein that interact physically with the conventional histone H3 (CENP-A) heterotetramer and is essential for its deposition at centromeres in vivo [, , , , ]. This protein has been implicated in many cancers [].
This entry includes human holliday junction recognition protein (HJURP) and its homologue, Scm3 from budding yeasts. HJURP is a histone chaperone that plays a central role in the incorporation and maintenance of histone H3-like variant CENP-A at centromeres []. Scm3 is a non-histone component of centromeric chromatin that binds to CenH3-H4 histones, which are required for kinetochore assembly. Scm3 is required for Cse4 (CENP- homologue) localisation and is required for its centromeric association [, ]. The histone H3 variant Cse4 replaces conventional histone H3 in centromeric chromatin and helps direct the assembly of the kinetochore. In addition, Scm3 has is required for G2/M progression []and is required to maintain kinetochore function throughout the cell cycle. Scm3 contains a nuclear export signal (NES). The N-terminal region of Scm3 is well conserved and functions as the CenH3-interacting domain, while the C-terminal region is variable in size and sometimes consists of DNA binding motifs [].
This entry includes histone H3 and its variant, CENP-A (Cse4 in budding yeast, Cnp1 in fission yeast, and CID/CenH3 in fruit flies). Two primate-specific forms of H3, known as H3.X and H3.Y, are found in the brain [].Histone H3 is one of the five histones, along with H1/H5, H2A, H2B and H4. Two copies of each of the H2A, H2B, H3, and H4 histones ensemble to form the core of the nucleosome []. The nucleosome forms octameric structure that wraps DNA in a left-handed manner. H3 is a highly conserved protein of 135 amino acid residues [, ]. Histones can undergo several different types of post-translational modifications that affect transcription, DNA repair, DNA replication and chromosomal stability.Eukaryotic centromeres consists of an unique nucleosome in which CENP-A can be found []. Human CENP-A nucleosome forms a histone octamer containing two each of histones H2A, H2B, H4 and CENP-A. Similar to the H3-containing nucleosome, the CENP-A nucleosome wraps DNA in a left-handed orientation [, ]. CENP-A nucleosomes function as a scaffold on which other kinetochore proteins assemble. CENP-A may serves as an epigenetic marker for kinetochore assembly []. Deposition of CENP-A to the centromere requires histone chaperone HJURP (Holliday junction recognition protein) [].
