Reassessing the contribution of the histone H3 tail to KRAB-DNMT3L-mediated epigenetic silencing
Neumann et al. introduced CHARM, a compact epigenetic silencer in which a histone H3 tail fused to DNMT3L was proposed to recruit and stimulate endogenous DNMT3A, enabling durable gene repression without a fused DNMT3A catalytic domain. Here, we evaluated the contribution of the H3 tail in independent reporter and endogenous-gene contexts. In an SNRPN reporter system, a KRAB-DNMT3L-dCas9…
A recent study investigates the role of a histone H3 tail in the KRAB-DNMT3L-mediated epigenetic silencing, which was previously proposed to enhance the effectiveness of a compact epigenetic silencer called CHARM. Researchers examined the contribution of the H3 tail in both reporter and endogenous gene contexts. In a SNRPN reporter system, a KRAB-DNMT3L-dCas9 construct lacking the H3 tail exhibited silencing kinetics similar to CRISPRcharm Kv2, and mutating a critical H3K4 residue to alanine in CRISPRcharm Kv2 did not hinder its silencing ability.
Similarly, transient delivery of editing mRNA to HEK293T cells showed that CRISPRcharm Kv2 did not consistently outperform the H3-tail-free construct at three endogenous loci, and mutating the critical H3K4 residue in CRISPRcharm Kv2 did not impair its activity. These findings suggest that the engineered H3 tail does not provide a general functional advantage within the KRAB-DNMT3L-dCas9 system under the tested conditions.
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