Structure of the SPRY domain of human Ash2L and its interactions with RbBP5 and DPY30

Bioinformatical and biochemical analyses suggested that the SPRY domain of Ash2L contains a large 44-residue unstructured loop (residues 402-445) in the middle of the domain (Supplementary information, Figure S1A, S1B and S1C). An Ash2L construct (Ash2L_SPRY) with a deletion of this loop retains the same HMT activity as the full-length Ash2L (Supplementary information, Figure S1D). We determined the crystal structure of Ash2L_SPRY using the single-wavelength anomalous dispersion method with mercury (MeHgAc)-derivative crystals, and refined to a resolution of 2.1 Å (Supplementary information, Table S1). The high-quality experimental electron density map enabled us to fit and refine the structure except for the C-terminal 13 residues (residues 511-523).

Ash2L_SPRY adopts a tadpole-like conformation with three recognizable modules, an 11-residue N-terminal pre-SPRY motif, a central 200-residue globular fold that forms the core of Ash2L_SPRY, followed by a 25-residue C-terminal post-SPRY motif (Figure 1B). Both the pre-SPRY and the post-SPRY motifs are short and composed of a 3₁₀ helix and either one or two β strands (Figure 1B). These two motifs form a two-stranded β sheet that protrudes from the globular SPRY domain, forming the tail of the tadpole-like structure (Figure 1B). The post-SPRY motif makes extensive contacts with one side of the β-sandwich of Ash2L_SPRY and thus plays an important role in stabilizing the core of the SPRY domain (Supplementary information, Figure S2A). The central core of Ash2L_SPRY adopts a distorted β-sandwich conformation, consisting of two layers of concave-shaped β-sheets (Figure 1B). All these β strands are arranged in an anti-parallel configuration. The two β-sheet layers stack together mainly through Van der Waals contacts by a group of hydrophobic residues (Supplementary information, Figure S2B). These internal hydrophobic residues are evolutionarily conserved from yeast to humans (Supplementary information, Figure S3), suggesting that all the Ash2L homologs share the similar SPRY fold as the human Ash2L_SPRY. The deleted 44-residue loop F' between strands β11 and β12, is away from the structural core, and thus is dispensable for the stability of the Ash2L_SPRY domain (Figures 1B). Of note, sequence alignment shows that the yeast Bre2 protein, a distant homolog of human Ash2L, contains two large loops, a 40-residue loop between strands β6 and β7 and another 112-residue loop connecting β11 and β12 (Supplementary information, Figure S3).

Log in or create a free account to read this content

Gain free access to this article, as well as selected content from this journal and more on nature.com

Access through your institution

or

Sign in or create an account

Continue with Google

Continue with ORCiD