title: Taspase1: a threonine aspartase required for cleavage of MLL and proper HOX gene expression.
abstract: The Mixed-Lineage Leukemia gene (MLL/HRX/ALL1) encodes a large nuclear protein homologous to Drosophila trithorax that is required for the maintenance of HOX gene expression. MLL is cleaved at two conserved sites generating N320 and C180 fragments, which heterodimerize to stabilize the complex and confer its subnuclear destination. Here, we purify and clone the protease responsible for cleaving MLL. We entitle it Taspase1 as it initiates a class of endopeptidases that utilize an N-terminal threonine as the active site nucleophile to proteolyze polypeptide substrates following aspartate. Taspase1 proenzyme is intramolecularly proteolyzed generating an active 28 kDa alpha/22 kDa beta heterodimer. RNAi-mediated knockdown of Taspase1 results in the appearance of unprocessed MLL and the loss of proper HOX gene expression. Taspase1 coevolved with MLL/trithorax as Arthropoda and Chordata emerged from Metazoa suggesting that Taspase1 originated to regulate complex segmental body plans in higher organisms.
authors.affiliation: Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: James J-D
authors.initials: JJ
authors.lastname: Hsieh
authors.forename: Emily H-Y
authors.initials: EH
authors.lastname: Cheng
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Korsmeyer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004331:Drosophila melanogaster; D010450:Endopeptidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation; D011495:Histone-Lysine N-Methyltransferase; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D051788:Myeloid-Lymphoid Leukemia Protein; D011480:Protease Inhibitors / Q000494:pharmacology; D011519:Proto-Oncogenes; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C497422:KMT2A protein, human; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D014157:Transcription Factors; D051788:Myeloid-Lymphoid Leukemia Protein; D013912:Threonine; D011495:Histone-Lysine N-Methyltransferase; C497423:Kmt2a protein, mouse; D010450:Endopeptidases; C480823:taspase1, human