Post-transcriptional regulation of inducible nitric oxide synthase in chronic lymphocytic leukemia B cells in pro- and antiapoptotic culture conditions.
Functional inducible NOS (iNOS) may be involved in the prolonged lifespan of chronic lymphocytic leukemia cells (B-CLL), although the exact mechanisms implicated remain elusive as yet. In this work, we have examined iNOS expression in normal B lymphocytes and B-CLL cells in pro- and antiapoptotic conditions. Our results demonstrate: (1) The existence of a new splice variant characterized by a complete deletion of exon 14 (iNOS 13-16(14del)), which was preferentially detected in normal B lymphocytes and may represent an isoform that could play a role in the regulation of enzyme activity. (2) The existence of another alternatively spliced iNOS mRNA transcript involving a partial deletion of the flavodoxin region (iNOS 13-16(neg)) was correlated to a decreased B-CLL cell viability. The 9-beta-D-arabinofuranosyl-2-fluoradenine or fludarabine (F-ara) treatment induced iNOS 13-16(neg) transcript variants, whereas IL-4 enhanced both the transcription of variants, including these exons (iNOS 13-16(pos)), and the expression of a 122 kDa iNOS protein. These results suggest that in B-CLL, a regulation process involving nitric oxide (.- NO) levels could occur by a post-transcriptional mechanism mediated by soluble factors. Our results also provide an insight into a new complementary proapoptotic action of F-ara in B-CLL by the induction of particular iNOS splice variants, leading to the activation of a caspase-3-dependent apoptotic pathway.
Departamento de Bioquímica, de la Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
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D000368:Aged; D000369:Aged, 80 and over; D017398:Alternative Splicing; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology; D001402:B-Lymphocytes / Q000201:enzymology; D001483:Base Sequence; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D007527:Isoenzymes; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D014158:Transcription, Genetic; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000494:pharmacology
D000970:Antineoplastic Agents; D007527:Isoenzymes; D012333:RNA, Messenger; D015847:Interleukin-4; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D004248:DNA (Cytosine-5-)-Methyltransferases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D014740:Vidarabine; C024352:fludarabine