4YPE: Ash1l Set Domain H2193f Mutant In Complex With S-adenosyl Methionine (sam)

ASH1L (absent, small, or homeotic-like 1) is a histone methyltransferase (HMTase) involved in gene activation that is overexpressed in multiple forms of cancer. Previous studies of ASH1L's catalytic SET domain identified an autoinhibitory loop that blocks access of histone substrate to the enzyme active site. Here, we used both nuclear magnetic resonance and X-ray crystallography to identify conformational dynamics in the ASH1L autoinhibitory loop. Using site-directed mutagenesis, we found that point mutations in the autoinhibitory loop that perturb the structure of the SET domain result in decreased enzyme activity, indicating that the autoinhibitory loop is not a simple gate to the active site but is rather a key feature critical to ASH1L function. We also identified a second loop in the SET-I subdomain of ASH1L that experiences conformational dynamics, and we trapped two different conformations of this loop using crystallographic studies. Mutation of the SET-I loop led to a large decrease in ASH1L enzymatic activity in addition to a significant conformational change in the SET-I loop, demonstrating the importance of the structure and dynamics of the SET-I loop to ASH1L function. Furthermore, we found that three C-terminal chromatin-interacting domains greatly enhance ASH1L enzymatic activity and that ASH1L requires native nucleosome substrate for robust activity. Our study illuminates the role of concerted conformational dynamics in ASH1L function and identifies structural features important for ASH1L enzymatic activity.
PDB ID: 4YPEDownload
MMDB ID: 132222
PDB Deposition Date: 2015/3/12
Updated in MMDB: 2017/10
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 4YPE: monomeric; determined by author and by software (PISA)
Molecular Components in 4YPE
Label Count Molecule
Protein (1 molecule)
Histone-lysine N-methyltransferase Ash1l(Gene symbol: ASH1L)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB