The Huntingtin-interacting protein SETD2/HYPB is an actin lysine methyltransferase

Abstract

The methyltransferase SET domain–containing 2 (SETD2) was originally identified as Huntingtin (HTT) yeast partner B. However, a SETD2 function associated with the HTT scaffolding protein has not been elucidated, and no linkage between HTT and methylation has yet been uncovered. Here, we show that SETD2 is an actin methyltransferase that trimethylates lysine-68 (ActK68me3) in cells via its interaction with HTT and the actin-binding adapter HIP1R. ActK68me3 localizes primarily to the insoluble F-actin cytoskeleton in cells and regulates actin polymerization/depolymerization dynamics. Disruption of the SETD2-HTT-HIP1R axis inhibits actin methylation, causes defects in actin polymerization, and impairs cell migration. Together, these data identify SETD2 as a previously unknown HTT effector regulating methylation and polymerization of actin filaments and provide new avenues for understanding how defects in SETD2 and HTT drive disease via aberrant cytoskeletal methylation.

SETD2 negatively regulates cell size through its catalytic activity and SRI domain

“…H3K36 methylation. However, as additional non-histone SETD2 substrates continue to be identified it is becoming clear that SETD2’s function extends beyond chromatin and transcription regulation (Park et al 2016; Chen et al 2017; Seervai et al 2020; Yuan et al 2020). Here, we report a novel cellular function of SETD2, namely the regulation of protein synthesis rate and cell size.…”

“…H3K36 methylation by SETD2/Set2 is conserved from yeast to humans and is involved in mRNA co-transcriptional processing, repression of cryptic transcription, and DNA damage repair (Yoh et al 2008; Luco et al 2010; Carvalho et al 2014; Mar et al 2017; Huang et al 2018). In addition, it has recently become clear that SETD2 also methylates non-histone substrates indicating that SETD2 has functions beyond chromatin regulation (Park et al 2016; Chen et al 2017; Seervai et al 2020; Yuan et al 2020). SETD2 is frequently mutated in cancer; 4.33% of all cancers carry SETD2 mutations, with endometrial cancer, clear cell renal cell cancer, bladder cancer and colorectal cancer being most frequently associated with SETD2 mutations (reviewed by Fahey and Davis 2017; Lu et al 2021).…”

Posttranslational modifications of the cytoskeleton

“…Other methylation sites on actin have been identified, but most are not functionally understood (Table 3). Recently, another SET‐domain containing protein, SETD2, has been shown to trimethylate actin on Lys68 (Seervai et al, 2020; Figures 1 and 3a). This enzyme can modify both monomeric and polymerized actin in vitro, but the modification is found almost exclusively in the polymerized cytoskeletal fraction in cells.…”

“…Lys68 methylation is enriched at the leading edge of the cell, where it colocalizes with a subset of the actin polymer. Disrupting Lys68 methylation by either knocking out Setd2 or expressing non‐methylatable actin (Lys68Arg or Lys68Ala) results in a decreased F‐actin to G‐actin ratio, disorganization of the actin network at the leading edge, and a reduction in cell motility (Seervai et al, 2020).…”

Methyltransferases in the Pathogenesis of Keratinocyte Cancers

“…SETD2 , frequently mutated in KCs, is the only known gene in human cells responsible for the trimethylation of H3K36 (H3K36me3) and has been shown to be involved in transcriptional initiation and elongation, alternative splicing, and DNA damage repair [ 87 , 88 ]. Beyond these canonical SETD2 functions, SETD2 has recently been shown to also methylate non-histone targets such as cytoskeletal proteins including α-tubulin and F-actin [ 89 , 90 , 91 , 92 ]. In this role, a deficiency of SETD2 can provoke both mitotic defects and impaired cellular migration.…”