Functions of the histone chaperones FACT and bromodomain AAA+ ATPases in heterochromatin spreading and centromere biology

• Applicant: Magdalena Murawska, Ph.D.
• Subject Area: General Genetics and Functional Genome Biology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 453441129

Histone chaperones are a diverse class of proteins that direct the assembly or disassembly of nucleosomes through preventing unintended interactions between highly charged histones with other cellular components. Through controlling histone delivery and incorporation into chromatin, histone chaperones play a pivotal role in maintaining genome stability and integrity. The genome of eukaryotic cells is organized into transcriptionally active (euchromatin) and silent domains (heterochromatin). Heterochromatin spreads along large domains to assure stable inheritance of gene expression patterns essential for cellular identity. The impairment of this process may cause incorrect expression or silencing of adjacent genes which has been implicated in several human diseases. The mechanisms that regulate the spreading of silent state along the chromatin fiber are not well understood. The first objective of this project is to analyze novel functions of a highly conserved histone chaperone complex FACT in heterochromatin spreading. Our unpublished data shows that the chaperone FACT is involved in controlling heterochromatin spreading in fission yeast, S. pombe. I will employ genetics, genomics and novel quantitative single cell assays to elucidate the molecular mechanism by which FACT controls spreading of the silent state. Given the conservation of FACT and its involvement in development, the results of this objective will be likely transferable to higher eukaryotes. In the second objective of this project, I will investigate the role of FACT and bromodomain AAA+ ATPases in centromere biology in S. pombe. Centromeres are specialized chromatin loci that guarantee proper chromosome segregation. Bromodomain AAA+ ATPases are novel histone chaperones that are highly misregulated in numerous cancers. They are emerging as compelling targets for anticancer therapies, however their molecular functions are unknown. Our unpublished data show association of FACT and bromodmain AAA+ ATPases with centromeric chromatin. Given the genetic interactions between those factors, I hypothesize that FACT and bromodomain AAA+ ATPases cooperate at centromeres. I will analyze the role of those chaperones in: (i) centromeric histone turnover, (ii) centromeric noncoding transcription, and (iii) the assembly of centromere components. Further, I will study spatial and temporal regulation of the chaperone recruitment to centromeric chromatin. I will employ state-of-the art genomic and transcriptomic approaches combined with cell cycle analysis. The results of this objective will bring novel insights into centromere assembly regulation by histone chaperones. Since small molecule inhibitors against the bromodomain AAA+ ATPases and FACT are being tested in preclinical studies, our results will also have likely a translational value.

• DFG Programme: Research Grants