Subunit Contributions to Histone Methyltransferase Activities of Fly and Worm Polycomb Group Complexes

Abstract

The ESC-E(Z) complex of Drosophila melanogaster Polycomb group (PcG) repressors is a histone H3 methyltransferase (HMTase). This complex silences fly Hox genes, and related HMTases control germ line development in worms, flowering in plants, and X inactivation in mammals. The fly complex contains a catalytic SET domain subunit, E(Z), plus three noncatalytic subunits, SU(Z)12, ESC, and NURF-55. The four-subunit complex is >1,000-fold more active than E(Z) alone. Here we show that ESC and SU(Z)12 play key roles in potentiating E(Z) HMTase activity. We also show that loss of ESC disrupts global methylation of histone H3-lysine 27 in fly embryos. Subunit mutations identify domains required for catalytic activity and/or binding to specific partners. We describe missense mutations in surface loops of ESC, in the CXC domain of E(Z), and in the conserved VEFS domain of SU(Z)12, which each disrupt HMTase activity but preserve complex assembly. Thus, the E(Z) SET domain requires multiple partner inputs to produce active HMTase. We also find that a recombinant worm complex containing the E(Z) homolog, MES-2, has robust HMTase activity, which depends upon both MES-6, an ESC homolog, and MES-3, a pioneer protein. Thus, although the fly and mammalian PcG complexes absolutely require SU(Z)12, the worm complex generates HMTase activity from a distinct partner set.

Adaptive selection and coevolution at the proteins of the Polycomb repressive complexes in Drosophila

“…The width and gray intensity of the connecting lines reflect the degree of the predicted interaction, which is stronger as the line gets wider and darker. (Ketel et al, 2005;Joshi et al, 2008) and SU(Z)12/CAF1 (Nowak et al, 2011) (Figure 6). Indeed, CAF1 is the only subunit of the Pcl-PRC2 complex that is not predicted to interact with any of the other subunits of the complex in the network, although such interactions have been experimentally inferred (Nowak et al, 2011).…”

Epigenetic regulation of aging stem cells

“…Another PcG gene implicated in adult stem cell function during aging is enhancer of zeste 2 (Ezh2), which comprises the methyltransferase activity of PRC2 (Kuzmichev et al, 2002;Muller et al, 2002;Ketel et al, 2005). In the hematopoietic system, Ezh2 does not appear to be required for stem and early progenitor cell function under normal steady-state conditions, as deletion of Ezh2 in all adult hematopoietic lineages causes a block in B-cell lineage production, but not in other lineages (Su et al, 2003).…”

Erratum: A positive role for polycomb in transcriptional regulation via H4K20me1

“…These observations were further confirmed in E(z) 731 mutant clones, where H3K27me3 levels and the expression of Sens were reduced, whereas the expression of Ubx was increased ( Figure 2G-2H' and Supplementary information, Figure S2E-S2E'). Furthermore, dramatic reduction in both the H3K27me3 levels and Sens expression was observed in clones of Su(z)12 4 ( Figure 2I-2J' and Supplementary information, Figure S2F-S2F'), a gene essential for the histone methyltransferase activity of E(z) in catalyzing H3K27me3 [41][42][43]. These results together suggest that Pc positively regulates transcription of Sens by recognizing H3K27me3 modification catalyzed by the intact PRC2.…”