Understanding the assembly and function of the CoREST co-repressor complex

The CoREST complex was initially identified as a cofactor of the REST

transcriptional repressor which plays important roles in regulating neuron-specific

gene expression and neuronal stem cell fate. The CoREST complex contains several

proteins including the histone deacetylases HDAC1 and HDAC2, the FADdependent

demethylase LSD1 and the co-repressor protein CoREST. HDAC1, the

first human HDAC identified, is only found in the nucleus and requires assembly

into one of several co-repressor complexes for full activity. LSD1 is a FADdependent

amine oxidase, which was identified as the first histone lysine

demethylase and is associated with both transcriptional repression and activation.

Whilst the structure of the complete LSD1/HDAC1/CoREST ternary complex is

unknown, the structure of LSD1 has been solved bound to the interaction region

from CoREST. In addition, previous studies in our group have reported the crystal

structures of the HDAC3/SMRT and HDAC1/MTA1 co-repressor complexes and

revealed that a SANT domain in both co-repressor proteins makes important

interactions with the HDAC catalytic domain. Furthermore, an inositol phosphate

molecule (IP) is sandwiched at the interface of the two proteins and regulates HDAC

activity.

I have successfully expressed and purified both the HDAC1/CoREST binary

complex and the LSD1/HDAC1/CoREST ternary complex using a mammalian cell

expression system. Both complexes are activated by inositol phosphates, and it has

also shown that there is cross-talk between HDAC active site and inositol

phosphates binding site. A new development enzymatic assay using 1D-NMR is

applied to investigate the relationship between LSD1 and HDAC1 in the CoREST

complex. Preliminary data highlight again the rigorous requirements of LSD1

substrate recognition.

I have used SAXS approach combined with negative stain EM and chemical crosslinking/

mass spectrometry to build a structural model for the CoREST complex.

This model provides the first image of the CoREST complex. Crystallization studies

are still underway to determine the high resolution crystal structure of the complex.