DNA Topoisomerase 1α Promotes Transcriptional Silencing of Transposable Elements through DNA Methylation and Histone Lysine 9 Dimethylation in Arabidopsis

THANH THERESA DINH; LEI GAO; XIGANG LIU; DONGMING LI; SHENGBEN LI; YUANYUAN ZHAO; MICHAEL O'LEARY; BRANDON LE; ROBERT J. SCHMITZ; PABLO MANAVELLA; SHAOFANG LI; DETLEF WEIGEL; OLGA PONTES; JOSEPH R. ECKER; XUEMEI CHEN

PLOS GENETICS

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2014

1553-7390

RNA-directed DNA methylation (RdDM) and histone H3K9 dimethylation (H3K9me2) are related transcriptional silencing mechanisms that target transposable elements (TEs) and repeats to maintain genome stability in plants. RdDM is mediated by small and long noncoding RNAs produced by the plant-specific RNA polymerases Pol IV and Pol V, respectively. Through a chemical genetics screen with a luciferase-based DNA methylation reporter, LUCL, we found that camptothecin, a compound with anti- cancer properties that targets DNA topoisomerase 1α (TOP1α) was able to de-repress LUCL by reducing its DNA methylation and H3K9me2 levels. Further studies with Arabidopsis top1α mutants showed that TOP1α silences endogenous RdDM loci by facilitating the production of Pol V-dependent long non-coding RNAs, AGONAUTE4 recruitment and H3K9me2 deposition at TEs and repeats. This study assigned a new role in epigenetic silencing to an enzyme that affects DNA topology.