Regulation of expression of two different transcripts of the NF-1 gene in neuroblastoma.
Neurofibromin, the gene product of the NF-1 gene is expressed in two isoforms. The m-RNA of NF-1 type II contains an insertion of 63 bases in the so called GAP-related domain, that distinguishes it from the type I transcript. By sequence homology neurofibromin is supposed to have a similar function in regulating activity of ras in intracellular signal transduction as the GTPase activating protein (GAP). Both transcripts of NF-1 are simultaneously expressed in different molar ratio in neuroblastoma tumors. 1) We examined 9 different neuroblastoma cell lines for the ratio of expression of NF-1 type I and type II. For quantification of the two transcripts we performed RT-PCR of the m-RNA of the neuroblastoma cells using primers designed to cover the GAP-related domain. We found values ranging from a more than 3-fold excess of type I transcript in the cell line Kelly to a slight excess of the type II transcript (I/II = 0.6) in the cell line IMR 5. 2) As there are indications that expression of NF-1 type II is related to the state of differentiation, we tried to shift expression of NF-1 from type I to type II by treatment of the neuroblastoma cells with retinoic acid. Treatment of Kelly cells with 5 microM retinoic acid for 24 h already lowered the excess of the type I transcript from 3-fold to an only 1.6-fold excess. An inversion of the molar ratio from an excess of the type I transcript to an excess of type II transcript would enable to investigate the different role of the two transcripts in the regulation of ras-activity and differentiation.
Girgert
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Klinikum Schnarrenberg, Department of Pediatric Surgery, University of Tübingen, Germany.
Schweizer
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P
D000970:Antineoplastic Agents / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D009447:Neuroblastoma; D025542:Neurofibromin 1; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000166:cytology / Q000502:physiology
D000970:Antineoplastic Agents; D025542:Neurofibromin 1; D011506:Proteins; D012333:RNA, Messenger; D014212:Tretinoin