Oligomerisation of THAP9 transposase: role of DNA and amino-terminal domains

Active DNA transposases like the Drosophila P element transposase (DmTNP) undergo oligomerisation as a prerequisite for transposition. Human THAP9 (hTHAP9) is a catalytically active but functionally uncharacterised homologue of DmTNP. Here we report (using co-IP, pull down, co-localization, PLA) that both the full length as well as truncated hTHAP9 and DmTNP (corresponding to amino-terminal DNA binding and Leucine-rich coiled coil domains) undergo homo-oligomerisation, predominantly in the nuclei of HEK293T cells. Interestingly, the oligomerisation is shown to be partially mediated by DNA. However, mutating the leucines (either individually or together) or deleting the predicted coiled coil region did not significantly affect oligomerisation. Thus, we highlight the importance of DNA as well as the amino-terminal regions of both hTHAP9 and DmTNP, for their ability to form higher order oligomeric states. We also report that Hcf-1, THAP1, THAP10 and THAP11 are possible protein interaction partners of hTHAP9. These studies lead to several questions about the different putative oligomeric states of hTHAP9 and how they may be related to its yet unknown physiological role as well as interaction partners.