Full-length H1.4 is methylated at six lysine residues by SET7/9. (A) Mutation of the four lysine residues K159, K171, K177 and K192 (K4R) in wild-type (WT) H1.4 reduces SET7/9-dependent methylation. The additional mutation of K121 and K129 (K6R) abolishes methylation of full-length H1.4 by SET7/9. (B) H1.4 is efficiently PARylated after methylation by SET7/9. H1.4 was first incubated with S-adenosyl-L-(methyl-14C) methionine (14C-SAM) and glutathione-S-transferase (GST) or SET7/9 and then incubated with ADP-ribosyltransferase-D1 (ARTD1) in the presence or absence of cold nicotinamide adenine dinucleotide (NAD)+. (C) H1.4 K6R is still modified by ARTD1. H1.4 WT and K6R were incubated with ARTD1 in the presence of 250 μM NAD+. PARylation was analyzed by Western blotting.