Chromobox protein homolog 5 (CBX5) (CBX5)

Chromobox protein homolog 5 (CBX5), commonly known as Heterochromatin Protein 1 alpha (HP1α), is a pivotal epigenetic reader that recognizes and binds to trimethylated lysine 9 on histone H3 (H3K9me3) via its N-terminal chromodomain (UniProt P45973). This interaction is essential for the formation and maintenance of constitutive heterochromatin, leading to the transcriptional silencing of specific genomic regions and ensuring genome stability through centromere and telomere organization (Wikipedia, 2024). Beyond gene silencing, CBX5 is involved in the DNA damage response and kinetochore assembly during mitosis (RefSeq, 2008). In clinical contexts, CBX5 is frequently overexpressed in various malignancies, such as glioblastoma and breast cancer, where it promotes tumor progression and chemoresistance (Connelly et al., 2016). Conversely, the loss of CBX5 has been identified as a driver of resistance to EGFR inhibitors in lung adenocarcinoma by upregulating the E2F1-BIRC5 axis (Bugide et al., 2023). CBX5 is also implicated in the activation of pathogenic fibroblasts in idiopathic pulmonary fibrosis (IPF), where its inhibition can promote metabolic reprogramming (NIH, 2025). Therapeutic development focuses on small-molecule inhibitors and peptidomimetics like UNC7047 and UNC7560, which target the chromodomain's aromatic cage to disrupt H3K9me3 binding and modulate gene expression (Simhadri et al., 2021).

Other names

Heterochromatin protein 1 alphaHP1 alphaHP1AHP1Hs alphaAntigen p25

Competitive inhibition of the chromodomain's aromatic cage to prevent binding to trimethylated lysine 9 of histone H3 (H3K9me3), leading to the derepression of silenced genes and alteration of chromatin structure.