Krüppel-associated box domain from human ZNF10 (KRAB)

Compact transcriptional repressor domain (~75 amino acids) from human zinc finger protein ZNF10. Originally characterized by Margolin et al. in 1994, KRAB achieves potent gene silencing by recruiting KAP1 corepressor complex, establishing stable heterochromatin marks. Standard effector domain for CRISPRi applications, achieving 90-99% gene knockdown when fused to dCas9.

Length: 219 bp

Class: Transcriptional Repressor

Origin: Human ZNF10 (Krüppel-associated box domain)

Characteristics

Compact 75-amino acid domain with two amphipathic alpha-helices forming the minimal repression module. Achieves 90-99% gene knockdown in CRISPRi applications when fused to dCas9. More specific than RNAi-based approaches with minimal off-target effects. Creates stable but reversible heterochromatin marks that can persist for weeks. Tandem KRAB repeats (2-3 copies) enhance repression strength for highly active genes. Compatible with diverse DNA-binding platforms including zinc fingers, TALEs, dCas9, and dCas12.

Applications: CRISPR interference for reversible gene silencing without DNA cutting. Genome-scale functional genomics screens for essential genes, tumor suppressors, and pathway analysis. Epigenome editing when fused to catalytically dead Cas9 or Cas12 variants for multiplexed transcriptional control. Gene therapy applications requiring stable but reversible transcriptional repression. Inducible gene silencing systems for temporal control of gene expression.

Limitations: Repression requires proximity to transcription start site with optimal positioning from −50 to +300 bp relative to TSS. Efficiency varies with chromatin context, promoter type, and baseline gene expression level. Single KRAB domain may provide insufficient repression for highly active genes or strong promoters. Heterochromatin marks can persist for weeks after removal of KRAB-dCas9, requiring active chromatin remodeling for full reactivation. Less effective at distal enhancers compared to promoter-proximal regions.

Mechanism: Recruits KAP1 (KRAB-associated protein 1, also known as TRIM28) corepressor complex, which in turn recruits histone deacetylases (HDACs), histone methyltransferase SETDB1, and heterochromatin protein 1 (HP1). Creates stable repressive chromatin state at target loci through H3K9me3 trimethylation and chromatin compaction.

Sequence

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References

  1. Margolin et al. (1994). Krüppel-associated boxes are potent transcriptional repression domains. Proc Natl Acad Sci USA - Margolin 1994 KRAB Repression
  2. Mali et al. (2013). CAS9 transcriptional activators for target specificity screening and paired nickases for cooperative genome engineering. Nat Biotechnol - Mali 2013 Cas9 Nickase
  3. Huntley et al. (2006). A comprehensive catalog of human KRAB-associated zinc finger genes: insights into the evolutionary history of a large family of transcriptional repressors. Genome Res - Huntley 2006 KRAB Zinc Fingers

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