LEDGF/p75 interaction network in the nucleosomal context

Eliska Koutna, Vanda Lux, Vaclav Veverka

Institute of Organic Chemistry and Biochemistry of the CAS, Prague, Czech Republic

 

Lens Epithelium Derived Growth Factor/p75 (LEDGF/p75 or PSIP1) is a transcriptional co-activator responsible for tethering other factors to the regions of actively transcribed genes using its PWWP domain that specifically binds di/trimethylated lysine 36 on histone 3 (H3K36me2/3). Cellular partners bound to its C-terminal integrase-binding domain (IBD) are thus drawn near the active chromatin. Through this interaction, LEDGF/p75 is associated with two distinct diseases, HIV infection and mixed-lineage (MLL) leukemia, and therefore becomes an attractive therapeutic target. The aim of our work is to understand the biological roles of LEDGF/p75 by tracking its interaction network in the nucleosomal context. The binding affinity for PWWP domain is six orders of magnitude higher when interacting with the whole nucleosome than H3K36me3 peptides or DNA alone because of its ability to bind both gyres and modified histone tail simultaneously. This would have an impact on the IBD domain-bound cellular partners that are readily available in the proximity of transcribed genes. To further elucidate the whole process, we examine the PWWP domain-nucleosome interactions using full-length LEDGF/p75, as well as LEDGF/p75 in complex with its known cellular partners. Our data present obtained cryo-EM structure of H3K36me2 nucleosome bound to the LEDGF/p75-POGZ(1117-1410) complex. These results will have an impact on current MLL leukemia drug discovery efforts by finding specific inhibitors of LEDGF/p75-MLL1 interaction and will contribute to a better understanding of transcriptional regulation in eukaryotic cells.