Author Correction: G-tract RNA removes Polycomb repressive complex 2 from genes (Nature Structural & Molecular Biology, (2019), 26, 10, (899-909), 10.1038/s41594-019-0293-z).

In the version of this article initially published, Fig. 4 included some errors. In Fig. 4c, the color for the left bar in each set of three bars (green) was incorrect; the correct color is orange (H2AK119ub, as in key). In Fig. 4d, top row, the downward error bars for H3K27me3 in the top middle plot (Fgf11 B) were incorrect; the correct s.d. in the negative direction is smaller for each. In Fig. 4d, bottom row, the far left downward error bar for HA-dCas9 in the left plot (Fgf11 A) was incorrect; the correct s.d. in the negative direction is larger. The errors have been corrected in the HTML and PDF versions of the article. (Figure presented.)

X-ray structure of 5-aminolaevulinate dehydratase, a hybrid aldolase

5-Aminolaevulinate dehydratase (ALAD) is a homo-octameric metallo-enzyme that catalyses the formation of porphobilinogen from 5-aminolaevulinic acid. The structure of the yeast enzyme has been solved to 2.3 A resolution, revealing that each subunit adopts a TIM barrel fold with a 39 residue N-terminal arm. Pairs of monomers wrap their arms around each other to form compact dimers and these associate to form a 422 symmetric octamer. All eight active sites are on the surface of the octamer and possess two lysine residues (210 and 263), one of which, Lys 263, forms a Schiff base link to the substrate. The two lysine side chains are close to two zinc binding sites one of which is formed by three cysteine residues (133, 135 and 143) while the other involves Cys 234 and His 142. ALAD has features at its active site that are common to both metallo- and Schiff base-aldolases and therefore represents an intriguing combination of both classes of enzyme. Lead ions, which inhibit ALAD potently, replace the zinc bound to the enzyme's unique triple-cysteine site