Bcl-2 Is a Therapeutic Target for Hypodiploid B-Lineage Acute Lymphoblastic Leukemia.

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. The highest rates of treatment failure occur in specific genetic subsets of ALL, including hypodiploid B-cell ALL (B-ALL), for which effective alternative therapies to current intensive chemotherapy treatments have yet to be developed. Here, we integrated biochemical and genomic profiling with functional drug assays to select effective agents with therapeutic potential against hypodiploid B-ALL.

Mutations in Hypodiploid Acute Lymphoblastic Leukemia.

Acute lymphoblastic leukemia (ALL) is an aggressive neoplasm of B- or T-lymphoid progenitors and is the commonest childhood tumor. ALL comprises multiple subtypes characterized by distinct genetic alterations, with stereotyped patterns of aneuploidy present in many cases. Although alterations of are common in many tumors, they are infrequent in ALL, with the exception of two ALL subtypes associated with poor outcome: relapsed disease and ALL with hypodiploidy.

Dysregulated human Tyrosyl-DNA phosphodiesterase I acts as cellular toxin.

Tyrosyl-DNA phosphodiesterase I (TDP1) hydrolyzes the drug-stabilized 3'phospho-tyrosyl bond formed between DNA topoisomerase I (TOPO1) and DNA. TDP1-mediated hydrolysis uses a nucleophilic histidine (Hisnuc) and a general acid/base histidine (Hisgab). A Tdp1Hisgab to Arg mutant identified in patients with the autosomal recessive neurodegenerative disease SCAN1 causes stabilization of the TDP1-DNA intermediate.

Tyrosyl-DNA phosphodiesterase I catalytic mutants reveal an alternative nucleophile that can catalyze substrate cleavage.

Tyrosyl-DNA phosphodiesterase I (Tdp1) catalyzes the repair of 3'-DNA adducts, such as the 3'-phosphotyrosyl linkage of DNA topoisomerase I to DNA. Tdp1 contains two conserved catalytic histidines: a nucleophilic His (His(nuc)) that attacks DNA adducts to form a covalent 3'-phosphohistidyl intermediate and a general acid/base His (His(gab)), which resolves the Tdp1-DNA linkage. A His(nuc) to Ala mutant protein is reportedly inactive, whereas the autosomal recessive neurodegenerative disease SCAN1 has been attributed to the enhanced stability of the Tdp1-DNA intermediate induced by mutation of His(gab) to Arg.

Tyrosyl-DNA phosphodiesterase I resolves both naturally and chemically induced DNA adducts and its potential as a therapeutic target.

DNA is subject to a wide range of insults, resulting from endogenous and exogenous sources that need to be metabolized/resolved to maintain genome integrity. Tyrosyl-DNA phosphodiesterase I (Tdp1) is a eukaryotic DNA repair enzyme that catalyzes the removal of covalent 3'-DNA adducts. As a phospholipase D superfamily member Tdp1 utilizes two catalytic histidines each within a His-Lys-Asn motif.

Analysis of the active-site mechanism of tyrosyl-DNA phosphodiesterase I: a member of the phospholipase D superfamily.

Tyrosyl-DNA phosphodiesterase I (Tdp1) is a member of the phospholipase D superfamily that hydrolyzes 3'-phospho-DNA adducts via two conserved catalytic histidines-one acting as the lead nucleophile and the second acting as a general acid/base. Substitution of the second histidine specifically to arginine contributes to the neurodegenerative disease spinocerebellar ataxia with axonal neuropathy (SCAN1). We investigated the catalytic role of this histidine in the yeast protein (His432) using a combination of X-ray crystallography, biochemistry, yeast genetics, and theoretical chemistry.