Taspase 1 and its sphere of activity – novel target proteins and influence on cell cycle progression

• Applicant: Dr. Astrid Hensel
• Subject Area: Cell Biology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409946033

Threonine Aspartase 1, abbreviated Taspase 1 contributes to the development of aggressive leukemias as well as to the formation of solid tumors. Therefore, this protease represents a promising therapeutic target for the inhibition of cancer cell proliferation. Prominent substrates of the mainly nuclear located Taspase 1 are transcriptional regulators such as the MLL protein or the general transcription factor TFIIA. A human genome-wide bioinformatic screen using the Taspase 1 consensus cleavage site could previously identify further putative substrates of Taspase 1.Besides various nuclear Taspase 1 targets, 19 putative targets of Taspase 1 were assigned an extranuclear localization. However, an experimental verification of most of those cytosolic Taspase 1 targets is still missing.Thus, one scientific objective of the proposed project is the experimental verification of predicted cytosolic substrates as well as the analysis of the cellular consequences of a Taspase 1-mediated cleavage for substrate function.Former studies revealed that Taspase 1 is involved in cell cycle control, but the underlying mechanisms have not been fully elucidated. Own preliminary work identified cyclin-dependent kinase inhibitor proteins (CDKIs) and further cell cycle regulator proteins as part of immunoprecipitated Taspase 1 complexes. Consequently, we hypothesized that Taspase 1 controls cell cycle progression not only by cleaving specific substrates but also via protein-protein interactions with other cell cycle regulators. To enable a more detailed spatio-temporal resolution of the Taspase 1 interactome, Taspase 1 complexes will be isolated from cell-fractions enriched in specific cell cycle phases or subcellular compartments and subsequently be investigated by mass spectrometry. Analysis of CDKIs protein stability and cell cycle kinetics in Taspase1-knockout cells will further reveal its influence on cell cycle control and differentiation processes. The insights gained within this research project will not only define the full functional range of Taspase 1 and the underlying regulatory mechanisms of its cleavage activity and cell cycle modulation, but may also provide meaningful strategies to tackle proliferating cells in cancer.

• DFG Programme: Research Grants