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Therapeutic resistance is a major obstacle in the treatment of acute myeloid leukemia (AML). Such resistance has been associated with rapid drug efflux mediated by the multidrug resistance gene 1 (MDR1; encoding P-glycoprotein) and more recently with expression of other novel proteins conferring multidrug resistance such as MRP1 (multidrug(More)
Compared with younger patients, elderly patients with acute myeloid leukemia (AML) respond poorly to conventional chemotherapy. To determine if this poor response is due to differences in the biologic characteristics of AML in the elderly, we studied 211 patients (161 de novo, 50 secondary AML) over 55 years of age (median, 68 years) registered to a single(More)
A fundamental catalytic principle for protein enzymes in the use of binding interactions away from the site of chemical transformation for catalysis. We have compared the binding and reactivity of a series of oligonucleotide substrates and products of the Tetrahymena ribozyme, which catalyzes a site-specific phosphodiester cleavage reaction:(More)
The ribozyme derived from the group I intron of Tetrahymena thermophila binds an exogenous guanosine nucleotide, which acts as the nucleophile in the sequence-specific cleavage of oligonucleotides. By examining the temperature dependence of the reaction under conditions where Km = Kd, we conclude the following: (1) Guanosine 5'-monophosphate (pG) binds to(More)
Several classes of ribozymes (catalytic RNA's) catalyze reactions at phosphorus centers, but apparently no reaction at a carbon center has been demonstrated. The active site of the Tetrahymena ribozyme was engineered to bind an oligonucleotide derived from the 3' end of N-formyl-methionyl-tRNA(fMet). This ribozyme catalyzes the hydrolysis of the aminoacyl(More)
The Tetrahymena thermophila L-21 ScaI ribozyme utilizes Mg2+ to catalyze a site-specific endonuclease reaction analogous to the first step of self-splicing. To better understand the contribution of Mg2+ to ribozyme activity, the Mg2+ concentration dependence of individual rate constants was examined at concentrations greater than those required for ribozyme(More)
The L-21 Sca I ribozyme derived from the group I intron of Tetrahymena thermophila pre-rRNA catalyzes an endonuclease reaction analogous to the first step of self-splicing. Guanosine (G) is bound by the ribozyme, and its 3'-hydroxyl group acts as the nucleophile. Here, we provide evidence that Km for G in several single-turnover reactions is equal to the(More)
A photoactivatable azidophenacyl group has been introduced into seven positions in the backbone of the 11 nucleotide invariant loop of U5 snRNA. By reconstituting depleted splicing extracts with reassembled U5 snRNP particles, molecular neighbors were assessed as a function of splicing. All cross-links to the pre-mRNA mapped to the second nucleotide(More)
Nucleotide analog interference mapping (NAIM) is a powerful method for identifying RNA functional groups involved in protein-RNA interactions. We examined particles assembled on modified U1 small nuclear RNAs (snRNAs) in vitro and detected two categories of interferences. The first class affects the stability of two higher-order complexes and comprises(More)
Chromosome translocations found in neoplasms often result in the creation of hybrid genes encoding chimeric proteins. This case study describes a patient with desmoplastic small round cell tumor (DSRCT) of the abdomen, an aggressive neoplasm characterized by translocation of chromosomes 11 and 22. Southern hybridization showed that the Ewing sarcoma gene(More)