Chromosome 11q23 translocations disrupting human Mixed Lineage Leukemia (MLL)gene are found in 80%of infantile leukemia and almost all cases of treatment induced secondary acute myeloid leukemia (AML). TheMLL gene is required for proper HOX gene expression. Our prior studies demonstrated that full-length 500kDMLL protein undergoes proteolysis to generate N-terminal 320kD (MLLN32 ) and C-terminal 180kD (MLLC18 )fragments. Processed MLL fragments form a complex to regulate the stability and availability of MLLN32 fordownstream gene regulation. We subsequently purified and cloned the responsible protease and entitled itTaspasel (Threonine Aspartase 1). The discovery of Taspasel initiates a new class of proteases utilizing their N-terminal Threonine of mature (3 subunit to cleave polypeptide substratesafter P1 aspartate. Preliminary studies in HeLa cells indicated the importance of Taspasel-mediated MLL cleavage in HOX geneexpression. Recently, we also identified a basal transcription factor, TFIIA, as a bona fide Taspasel substrate.To investigate the physiological functions of Taspasel in vivo, we generated Taspasel knockout mice. Initialstudies on Taspasel deficient animals indicate the essential role of Taspasel in body patterning, nervous systemdevelopment, and cell cycle progression. With these unique reagents, we will further interrogate Taspaselfunctions via the following specific aims:
Specific Aim 1 : We will characterize the role of Taspasel in mouse embryonic development. It entails thecreation of straight and conditional Taspasel knockout mice to determine whether Taspasel deficiency in miceresults in embryonic lethality, homeotic transformations and/or other developmental abnormalities. We will dissectthe mechanisms by which Taspasel regulates Hox gene expression.
Specific Aim 2 : We will investigate the requirement of Taspasel in normal cell cycle progression. We will startwith studying cell cycle progression defects in Taspasel deficient animals and cells, followed by dissecting themechanisms by which Taspasel regulates cell cycle progression and perform genetic reconstitutions ofprocessed MLL family proteins into Taspasel deficient cells to determine whether MLL proteolysis regulates cellproliferation.
Specific Aim 3 : We will perform studies to identify additional Taspasel substrates and will validate theirimportance in vitro and in vivo. We will utilize 2-D difference in-gel electrophoresis in conjunction with massspectrometry for the initial discovery, followed by phenotypic analyses of individual non-cleavable substrates. Since deregulation of HOX genes and cell cycle genes contribute to tumorigensis, this combined genetic,biochemical, and proteomic approach to investigate Taspasel functions will provide further insights regardingMLL leukemia and may lay the foundation for future development of Taspasel inhibitors as anti-cancertherapeutics.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-ONC-U (90))
Program Officer
Mufson, R Allan
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Sloan-Kettering Institute for Cancer Research
New York
United States
Zip Code
Hsieh, James J; Manley, Brandon J; Khan, Nabeela et al. (2017) Overcome tumor heterogeneity-imposed therapeutic barriers through convergent genomic biomarker discovery: A braided cancer river model of kidney cancer. Semin Cell Dev Biol 64:98-106
Dong, Yiyu; Manley, Brandon J; Becerra, Maria F et al. (2017) Tumor Xenografts of Human Clear Cell Renal Cell Carcinoma But Not Corresponding Cell Lines Recapitulate Clinical Response to Sunitinib: Feasibility of Using Biopsy Samples. Eur Urol Focus 3:590-598
Hsieh, James J; Purdue, Mark P; Signoretti, Sabina et al. (2017) Renal cell carcinoma. Nat Rev Dis Primers 3:17009
Xu, Haiming; Valerio, Daria G; Eisold, Meghan E et al. (2016) NUP98 Fusion Proteins Interact with the NSL and MLL1 Complexes to Drive Leukemogenesis. Cancer Cell 30:863-878
Voss, Martin H; Hsieh, James J (2016) Therapeutic Guide for mTOuRing through the Braided Kidney Cancer Genomic River. Clin Cancer Res 22:2320-2
Takeda, Shugaku; Sasagawa, Satoru; Oyama, Toshinao et al. (2015) Taspase1-dependent TFIIA cleavage coordinates head morphogenesis by limiting Cdkn2a locus transcription. J Clin Invest 125:1203-14
Liu, Han; Westergard, Todd D; Cashen, Amanda et al. (2014) Proteasome inhibitors evoke latent tumor suppression programs in pro-B MLL leukemias through MLL-AF4. Cancer Cell 25:530-42
Dong, Yiyu; Van Tine, Brian A; Oyama, Toshinao et al. (2014) Taspase1 cleaves MLL1 to activate cyclin E for HER2/neu breast tumorigenesis. Cell Res 24:1354-66
Oyama, Toshinao; Sasagawa, Satoru; Takeda, Shugaku et al. (2013) Cleavage of TFIIA by Taspase1 activates TRF2-specified mammalian male germ cell programs. Dev Cell 27:188-200
Takeda, Shugaku; Liu, Han; Sasagawa, Satoru et al. (2013) HGF-MET signals via the MLL-ETS2 complex in hepatocellular carcinoma. J Clin Invest 123:3154-65

Showing the most recent 10 out of 16 publications