Thomas Kusch Assistant Professor Rutgers University Dept. Molecular Biology & Biochemistry Nelson Biological Labs, Room A123 Piscataway, NJ 08854 (732) 445-6895 FAX - 6186 kusch@biology.rutgers.edu Visit the Kusch Lab

Epigenetic mechanisms of gene expression and genome stability, Multiprotein complexes modulating chromatin structure, Histone variants

The genome of the eukaryotic cell is packaged into a nucleoprotein structure called chromatin. The fundamental repeating unit of chromatin is the nucleosome, consisting of 147 base pairs of DNA wrapped around a histone octamer. While necessary to package the genome in a tight space, nucleosomes form an obstacle for transcription, DNA replication, recombination and repair. To alter histone-DNA interactions, cells employ three basic mechanisms. These are i) ATP-dependent chromatin remodeling, ii) the incorporation of histone variants into nucleosomes, and iii) posttranslational modification of histones.

In higher eukaryotes, posttranslational modifications of histones and the incorporation of histone variants are tightly regulated and occur in precise temporal and spatial patterns during development. These – usually inheritable - changes help establish and maintain specific gene expression programs that eventually determine the identity of tissues and organs. Remarkably, certain chromatin modifications are not only important for development, but also play important roles during DNA repair, replication, and/or recombination. Taken together, chromatin bears pivotal epigenetic information for development and maintenance of genomic integrity. Not surprisingly, the deregulation of epigenetic mechanisms is linked to cancer, aging, hereditary and neurodegenerative diseases.
Research in our laboratory focuses on multiprotein complexes, which regulate epigenetic mechanisms. We are utilizing a broad array of methods including proteomics, genetics, reverse genetics, biochemistry, and functional genomics. The organism of our choice is the fruit fly Drosophila melanogaster for its excellence as model for developmental as well as chromatin-related studies. Of particular interest are currently:

1) The functional dissection of the dTip60 complex.
The dTip60 complex is a structurally and functionally highly conserved complex and contains multiple tumor suppressors including the histone variant H2Av. H2Av is a guardian of genome stability and is involved in developmental gene regulation. We wish to get a better understanding of the role of different subunits in DNA repair and transcriptional regulation on both molecular and cellular levels.

2) Complexes involved in H2Av deposition and exchange
Besides the dTip60 complex, we have characterized at least two more complexes targeting H2Av. Like the dTip60 complex, these complexes function in DNA damage response and transcription. We currently are studying the functional relationship between these three complexes.

3) The function of common ‘modules’ within chromatin-restructuring complexes

Chromatin remodeling complexes of our interest contain various subunits that are likely to ‘recognize’ certain posttranslational modifications within nucleosomes. Our goal is to identify these modifications and their recognition modules. These studies will help us to understand how different complexes can induce stepwise changes within chromatin structure.

Selected Publications

Kusch T, Workman JL. (2007) Histone variants and complexes involved in their exchange.
Subcell Biochem. 41:91-109.

Guelman S, Suganuma T, Florens L, Swanson SK, Kiesecker CK, Kusch T, Anderson S, Yates JR 3rd, Washburn MP, Abmayr SM, Workman JL (2006). Host Cell Factor (dHCF) and an uncharacterized SANT-domain protein are stable components of ATAC, a novel dAda2A/dGcn5-containing HAT complex in Drosophila. Mol Cell Biol. 26: 871-82.

Jin J, Cai Y, Li B, Conaway RC, Workman JL, Conaway JW, Kusch T (2005). In and Out: Histone Variant Exchange in Chromatin. Trends Biochem Sci. 30 (12): 680-7.

Cai Y, Jin J, Florens L, Swanson SK, Kusch T, Li B, Workman JL, Washburn MP, Conaway RC, Conaway JW (2005). The mammalian YL1 protein is a shared subunit of the TRRAP/TIP60 histone acetyltransferase and SRCAP complexes. J Biol Chem 280:13665-70.

Kusch T, Florens L, Macdonald WH, Swanson SK, Glaser RL, Yates JR 3rd, Abmayr SM, Washburn MP, Workman JL (2004). Acetylation by Tip60 is required for selective histone variant exchange at DNA lesions. Science 306 (5704):2084-7.

Carrozza, MJ, Kusch T, Workman JL (2003). Repairing of nucleosomes during transcription. Nat Struct Mol Biol. 10:879-80.

Kusch T, Guelman S, Abmayr, SM, Workman JL (2003). Two Drosophila Ada2 homologues function in different multiprotein complexes. Mol Cell Biol. 23:3305-19.

Howe L, Kusch T, Muster N, Chaterji R, Yates JR 3rd, Workman JL (2002). Yng1p modulates the activity of Sas3p as a component of the yeast NuA3 histone acetyltransferase complex. Mol Cell Biol. 22:5047-53.

Kusch T, Storck T, Walldorf U, Reuter R (2002). Brachyury proteins regulate target genes through modular binding sites in a cooperative fashion. Genes Dev. 16:518-29.

Kusch T, Reuter R (1999). Functions for Drosophila brachyenteron and fork head in mesoderm specification and cell signalling. Development 126:3991-4003.