Elucidating the Functional Role of the Actin-related Proteins, ACTL6A and ACTL6B, in ATP-Dependent Chromatin Remodeling

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PROJECT SUMMARY/ABSTRACT Recent exome sequencing efforts have implicated alterations that occur within the actin-related proteins (Arps), ACTL6A and ACTL6B, in both cancer and neurodevelopmental disorders. These highly conserved and tissue- specific protein paralogues are subunits of multi-component molecular machines that use the energy derived from ATP hydrolysis to modify chromatin architecture, and hence modulate gene expression. ACTL6A and ACTL6B are subunits of four major chromatin regulators known to remodel the architecture of chromatin: (1) the Tip60/NuA4 histone acetyl transferase, and the (2) INO80, (3) SRCAP, and (4) mammalian SWI/SNF (mSWI/SNF), also called BRG1/BRM Associated Factors (BAF) ATP-dependent chromatin remodeling complexes. The mSWI/SNF complex has been particularly implicated in a range of neurodevelopmental disorders and in over 20% of all cancers. However, despite these intriguing genetic studies as well as data suggesting that Arps are required for proper chromatin regulation, there is very little understanding regarding the biochemical and genome-wide role of Arps in chromatin remodeling activities. My proposed research plan aims to further our understanding of the molecular mechanisms of disease conferred by mutant ACTL6A and ACTL6B by identifying functional regions and the biochemical and genome-wide activities of the Arps. Aim 1 investigates the functional regions and biochemical activities contributed to chromatin remodeling complexes by ACTL6A and ACTL6B in WT conditions and mutant settings linked with neurodevelopmental disorders. More specifically, Sub- aim 1A seeks to compare the interactome of the ACTL6 subunits. Sub-aim 1B unbiasedly compares the protein interactions of WT and mutant ACTL6A/B. Sub-aim 1C focuses on mSWI/SNF complexes to assess their histone binding and enzymatic activities in WT forms and in those complexes bearing Arps with disease-relevant mutations. Aim 2 dissects the genome-wide function of the Arps by comparing a WT control to induced pluripotent stem cells (iPSCs) engineered to have disease-relevant mutations. Sub-aim 2A dissects the chromatin accessibility and gene expression profiles of WT and mutant iPSCs. And, Sub-aim 2B looks at the genome targeting of the mutant and WT ACTL6 subunits and the four major protein complexes known to bind them. Successful completion of these aims will provide new insights regarding the interplay of chromatin remodeling complexes unified by the same family of Arp proteins, define the molecular mechanisms of ACTL6A/B-binding proteins in normal and disease states, and suggest novel targeted therapeutic approaches for cancer and intellectual disabilities. The research laboratory of Dr. Cigall Kadoch is the ideal setting to conduct the disease-oriented research at the interface between biochemistry and functional genomics detailed in this proposal. Training in state-of-the-art biochemical, enzymatic, and genomic assays, as well as the professional development Dr. Kadoch provides on scientific communication, networking, leadership, and advocacy will allow to me to become a capable independent scientist.