HP1BP3 is a histone H1-like linker histone variant essential for chr1 architecture and gene regulation. Structurally, HP1BP3 contains three globular domains and a positively charged C-terminal region that enable nucleosome binding regulated by chaperones NPM1 and TAF-I 1. HP1BP3 functions as a chr1 retention factor for co-transcriptional microRNA processing by recruiting and stabilizing the Drosha-DGCR8 microprocessor complex at actively transcribed miRNA loci 2. The protein maintains heterochromatin integrity during cell cycle progression and regulates G1 phase duration to control proliferative capacity [UniProt annotation]. In cancer contexts, HP1BP3 cooperates with EZH2 to epigenetically activate WNT7B, promoting glioblastoma stem cell self-renewal and temozolomide resistance 3. HP1BP3 localizes to telomeres in ALT cancer cells, where it maintains telomere chr1 compaction and H3K9me3 marks, supporting telomere stability 4. In genomic imprinting, HP1BP3 interacts with PGC7 to maintain Meg3-DMR methylation by regulating chr1 configuration and antagonizing DNMT3A binding 5. HP1BP3 demonstrates non-redundant functions: Hp1bp3-knockout mice exhibit 60% neonatal lethality and 20% growth retardation in survivors 6, and knockdown studies identify HP1BP3 as significantly impacting glioma cell proliferation 7. Emerging evidence suggests HP1BP3 variants may contribute to Chiari malformation type 1 pathogenesis 8.