Successful treatment of lymphoid blastic crisis in chronic myelogenous leukemia with the additional bcr/abl transcript using imatinib-combined chemotherapy and high-dose chemotherapy with allogeneic bone marrow stem cell transplantation.

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder characterized by the presence of the Philadelphia chromosome. Although the major BCR/ABL transcript is present in majority of CML patients, the minor BCR/ABL transcript is rarely reported as an additional chromosomal abnormality related to the progression of CML. We describe the case of a 37-year-old woman who had CML and pain in the extremities. She was diagnosed with lymphoid blast crisis of CML on the basis of the following findings: presence of promyelocytes, myelocytes, and metamyelocytes in peripheral blood smear; detection of major and minor BCR/ABL transcripts by polymerase chain reaction analysis; proliferation of lymphoblastic cells with abnormal B-cell phenotype; and aberrant expression of myeloid antigens in the bone marrow. The patient underwent one course of idarubicin and cytosine arabinose therapy combined with imatinib followed by daunorubicin/cyclophosphamide plus vincristine and prednisone/L: -asparaginase (DNR/COP/L: -ASP) therapy, high-dose cytosine arabinose, and CHOP therapy (cyclophosphamide, doxorubicin, vincristine, and prednisolone). Subsequently, the patient underwent high-dose chemotherapy (total body irradiation and cyclophosphamide) followed by allogeneic bone marrow stem cell transplantation from a human leukocyte antigen (HLA)-matched unrelated donor. After these treatments, the patient was disease-free for 19 months. Our case suggests that these treatments may be feasible, safe, and effective for the treatment of patients with blast crisis CML expressing the minor BCR/ABL transcript.

Nascent peptide-mediated translation elongation arrest coupled with mRNA degradation in the CGS1 gene of Arabidopsis.

Expression of the Arabidopsis CGS1 gene that codes for cystathionine gamma-synthase is feedback regulated at the step of mRNA stability in response to S-adenosyl-L-methionine (AdoMet). A short stretch of amino acid sequence, called the MTO1 region, encoded by the first exon of CGS1 itself is involved in this regulation. Here, we demonstrate, using a cell-free system, that AdoMet induces temporal translation elongation arrest at the Ser-94 codon located immediately downstream of the MTO1 region, by analyzing a translation intermediate and performing primer extension inhibition (toeprint) analysis. This translation arrest precedes the formation of a degradation intermediate of CGS1 mRNA, which has its 5' end points near the 5' edge of the stalled ribosome. The position of ribosome stalling also suggests that the MTO1 region in nascent peptide resides in the ribosomal exit tunnel when translation elongation is temporarily arrested. In addition to the MTO1 region amino acid sequence, downstream Trp-93 is also important for the AdoMet-induced translation arrest. This is the first example of nascent peptide-mediated translation elongation arrest coupled with mRNA degradation in eukaryotes. Furthermore, our data suggest that the ribosome stalls at the step of translocation rather than at the step of peptidyl transfer.

S-adenosyl-L-methionine is an effector in the posttranscriptional autoregulation of the cystathionine gamma-synthase gene in Arabidopsis.

Cystathionine gamma-synthase, the first committed enzyme of methionine biosynthesis in higher plants, is encoded by the CGS1 gene in Arabidopsis thaliana. We have shown previously that the stability of the CGS1 mRNA is negatively regulated in response to methionine application [Chiba, Y., Ishikawa, M., Kijima, F., Tyson, R. H., Kim, J., Yamamoto, A., Nambara, E., Leustek, T., Wallsgrove, R. M. & Naito, S. (1999) Science 286, 1371-1374]. To determine whether methionine itself is the effector of the CGS1 exon 1-mediated posttranscriptional regulation, we carried out transfection experiments. The results suggested that, rather than methionine, S-adenosyl-L-methionine (AdoMet), or one of its metabolites, acts as the effector of this regulation. To further identify the actual effector, we exploited the wheat germ in vitro translation system. The effects of various metabolites and analogs of AdoMet were tested by using RNA carrying a CGS1 exon 1-reporter fusion. These tests identified AdoMet as the effector of this regulation. S-adenosyl-L-ethionine, an analog of AdoMet, also had effector activity. A. thaliana mto1 mutants, which are deficient in this regulation, showed a much reduced response to AdoMet in vitro, with a leaky allele showing a less reduced response. RNA translated in vitro in the presence of AdoMet contained a 5'-truncated RNA species, similar to the one that we previously suggested was an in vivo degradation intermediate of CGS1 mRNA. Together, the results show that the basic reactions of CGS1 exon 1-mediated posttranscriptional regulation occur in the wheat germ in vitro translation system, and that AdoMet acts as the effector.