Journal Article

Structural basis for uracil removal from DNA by human SMUG1

Ludäscher, Julian M., Scaletti Hutchinson, Emma, Carlsson, Jens, Walse, Ellen, Gajdos, Lukas, Pach, Szymon, Wiita, Elisee, Vila-Julià, Guillem, Shahid, Saher, Helleday, Thomas, Jemth, Ann-Sofie, Cabeza de Vaca, Israel, Aggarwal, Swati, Mortusewicz, Oliver, Stenmark, Pål

2026

Overview

Human single-strand-selective monofunctional uracil DNA glycosylase 1 (hSMUG1) removes uracil, 5-hydroxymethyluracil (5hmU) and 5-fluorouracil (5FU) from DNA, thereby initiating the base excision repair (BER) process. hSMUG1 is important for maintaining genomic integrity and plays a significant role in cancer biology. Here, we present the structures of hSMUG1, including complexes with products (uracil and 5FU) and an enzyme-product complex of hSMUG1 with double-stranded DNA (dsDNA). Analysis of our hSMUG1-dsDNA complex reveals how uracil is flipped out of the dsDNA for excision and identifies key residues that we confirm to be critical for both DNA binding and enzymatic activity. Furthermore, our hSMUG1 substrate complexes, molecular dynamics simulations and neutron diffraction data suggest a mechanism by which the substrate uracil rotates following base excision. The structural and functional information presented here will be highly useful for the future development of inhibitors and/or activators targeting hSMUG1. DNA repair enzymes such as SMUG1 are essential for maintaining genomic integrity and have important implications in cancer biology. Here, the authors present the structures of human SMUG1 and reveal how it recognises and excises mutagenic uracil from DNA, identifying key residues and proposing a post excision rotation mechanism.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 5-Fluorouracil / 631/45/147 / 631/45/535/1266 / 631/45/607/1159 / 631/535 / 82/80 / 82/83 / Base excision repair / Biology / Cancer / Crystallography, X-Ray / Deoxyribonucleic acid / DNA / DNA - chemistry / DNA - metabolism / DNA glycosylase / DNA methylation / DNA Repair / Enzymatic activity / Enzymes / Excision Repair / Fluorouracil - chemistry / Fluorouracil - metabolism / Genomics / Humanities and Social Sciences / Humans / Hydrogen bonds / Integrity / Molecular dynamics / Molecular Dynamics Simulation / multidisciplinary / Neutron diffraction / Pentoxyl - analogs & derivatives / Pentoxyl - chemistry / Pentoxyl - metabolism / Protein Binding / Proteins / Residues / Science / Science (multidisciplinary) / SMUG1 protein / Structure-function relationships / Uracil / Uracil - analogs & derivatives / Uracil - chemistry / Uracil - metabolism / Uracil-DNA glycosidase / Uracil-DNA Glycosidase - chemistry / Uracil-DNA Glycosidase - genetics / Uracil-DNA Glycosidase - metabolism