Co-translational protein complex formation.

Multi-protein complexes constitute some of the most relevant molecular units of cellular function. Despite their important role it remains mysterious how eukaryotic cells manage to assemble with precision hundreds of different complexes in the crowded cytoplasmic compartment that produces thousands of nascent proteins at the same time. Work from our laboratory demonstrated that assembly of protein complexes can be initiated on nascent proteins as they emerge from the ribosome (Halbach et al, 2009). We are investigating the functional significance of co-translational protein interactions (Williams and Dichtl, 2018). This work was supported by an ARC Discovery Project grant DP140101509 to study the mechanisms of protein complex formation.

Pathways for intracellular assembly of protein complexes (Williams and Dichtl, 2018).

The function and regulation of the Set1C histone methyltransferase.
Histone modifying enzymes regulate diverse processes that occur in association with chromatin. We performed extensive yeast two-hybrid screening in order to identify novel cellular roles for the Set1C chromatin-modifying enzyme. This resulted in a recent publication in Science (Acquaviva et al., 2013), which identified the molecular mechanisms that link chromatin modification of histone H3 lysine 4 to the formation of double strand DNA breaks, to initiate the process of meiotic recombination.

Methylation of histone H3 lysine 4 (H3K4) by Set1 complex/COMPASS is a hallmark of eukaryotic chromatin but it remains poorly understood how this post-translational modification contributes to the regulation of biological processes like the cell cycle. We identified a H3K4 methylation dependent pathway in Saccharomyces cerevisiae that governs toxicity towards benomyl, a microtubule destabilizing drug. Our work revealed a role for H3K4 methylation in the coordination of cell cycle progression and proper assembly of the mitotic spindle during mitosis (Beilharz et al., Genetics, 2017).

Scheme illustrating the role of H3K4 methylation by Set1C histone methyltransferase in linking G1 transcriptional control to chromosome segregation during mitosis (Beilharz et al., 2017).

The role and regulation of alternative polyadenylation in health and disease.

Pre-mRNA 3’ end formation is an essential RNA maturation step that impacts on virtually all aspects of mRNA function. The process adds a tail of approximately 250 adenosines to the 3’ end of mRNA and determines the length of the 3’ Un-Translated Region (3’UTR), which is targeted by a large number of regulatory factors.

Yeast and mammalian 3′ end formation machineries. Homologous components are color coded. The gel on the left shows a silver stain of purified CPF factor from yeast (Dichtl et al., 2002)

Control of 3’UTR length via alternative Polyadenylation (APA) is an important mechanism to control gene expression. We are interested in the regulation of APA and how it is integrated with cellular signaling pathways.

Alternative Polyadenylation signal use, creates mRNA isoforms with differing 3’UTR length. APA doesn’t affect the protein product but has a role in regulation by providing variable access to regulatory RNAs and RNA binding proteins (Lee Henneken, Honours thesis 2018).