SETDB2

SETDB2 Full Name

SET domain, bifurcated 2

SETDB2 Introduction

SET domain bifurcated 2 (SETDB2), also known as CLLL8 or CLLD8, is a histone lysine methyltransferase (HKMT) belonging to the SUV39H family of SET domain-containing proteins. The SETDB2 gene is located on human chromosome 13q14.2, a region frequently deleted in chronic lymphocytic leukemia (CLL) and other B-cell malignancies, suggesting a tumor suppressor function. SETDB2 specifically catalyzes the trimethylation of histone H3 at lysine 9 (H3K9me3), a well-characterized repressive epigenetic mark associated with heterochromatin formation and transcriptional silencing.

Figure 1. Strcuture of Protein SETDB2.(Mahana Y, Ariyoshi M, Nozawa R S, et al. 2024)

Epigenetic Regulation of Chromosome Segregation and Genomic Stability
A specialized and critical function of SETDB2 is its role in maintaining genomic stability during cell division. SETDB2 localizes to pericentromeric heterochromatin regions, where it catalyzes H3K9 trimethylation to establish a chromatin environment permissive for proper kinetochore assembly and microtubule attachment. Loss of SETDB2 function results in centromeric chromatin decompaction, defective chromosome congression, and an increased frequency of lagging chromosomes and micronuclei formation. This function is mediated through the interaction of SETDB2 with heterochromatin protein 1 (HP1) isoforms, particularly HP1α, which recognize and bind the H3K9me3 mark deposited by SETDB2, reinforcing heterochromatin spreading and structural integrity.

SETDB2 in Hematological Malignancies and Innate Immunity
SETDB2 was originally identified through its frequent deletion or epigenetic silencing in chronic lymphocytic leukemia, where loss of its tumor-suppressive H3K9me3 activity may contribute to genomic instability and disease progression. Beyond cancer, SETDB2 plays a regulatory role in innate immunity: it is an interferon-stimulated gene (ISG) that is transcriptionally upregulated by type I interferon signaling. SETDB2 subsequently functions as a negative feedback regulator of the antiviral response by depositing H3K9me3 at the promoters of pro-inflammatory cytokine genes including CXCL1 and TNF, limiting excessive inflammation. In the context of viral infection (e.g., influenza, Zika virus), SETDB2-mediated silencing of cytokine loci helps prevent immunopathology, highlighting its dual role in maintaining both genomic and immunological homeostasis.

Alternate Names for SETDB2

SETDB2; SET domain, bifurcated 2; CLLD8; CLLL8; KMT1F; C13orf4; histone-lysine N-methyltransferase SETDB2; lysine N-methyltransferase 1F; chronic lymphocytic leukemia deletion region 8; chronic lymphocytic leukemia deletion region gene 8 protein;

• 1.Mahana Y, Ariyoshi M, Nozawa R S, et al. Structural evidence for protein-protein interaction between the non-canonical methyl-CpG-binding domain of SETDB proteins and C11orf46. Structure, 2024, 32(3): 304-315. e5.