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Splicing Isoforms (splicing + isoform)
Selected AbstractsNeonatal isoimmune thrombocytopenia caused by type I CD36 deficiency having novel splicing isoforms of the CD36 geneEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 1 2008Takeshi Taketani Abstract Neonatal alloimmune thrombocytopenia (NAIT) occurs because of transplacentally acquired maternal platelet alloantibodies. Most of the alloantibodies are against human platelet antigens, but the alloantibody against CD36 is rare. A full-term female baby was delivered by a mother who experienced two spontaneous abortions. The baby had thrombocytopenia with cephalhematoma. The platelet count increased by immunoglobulin therapy (400 mg/kg) for 3 d. Platelet antibody was detected in the postpartum maternal serum. The specificity of the antibody directed against platelets was identified as anti-Naka (CD36). Flow cytometric analysis showed no expression of CD36 in both platelets and monocytes from mother. Mutation analysis revealed two different splicing isoforms of maternal CD36 mRNA. One allele was exon 4 skipping, another was exon 9 skipping, both of which led to a frameshift and produced a truncated CD36 protein. These results indicate that NAIT is caused by maternal CD36 deficiency having CD36 splicing abnormalities. [source] Two splicing isoforms of the Y-box protein ctYB-1 appear on the same mRNA moleculeFEBS JOURNAL, Issue 1 2007Dmitry Nashchekin Y-box proteins constitute an evolutionarily conserved family of DNA- and RNA-binding proteins involved in the regulation of transcription and translation. In the dipteran Chironomus tentans, a homologue to the vertebrate Y-box protein YB-1 was recently characterized and designated ctYB-1. It is transferred from nucleus to cytoplasm bound to mRNA and is likely to affect translation. It appears in two size variants, p40 and p50. We further analysed the two size variants and their interaction with mRNA. Southern blot analysis, in situ hybridization and RT-PCR analysis suggested that there is just one YB-1 gene, and that the two size variants represent splicing isoforms. In a C. tentans epithelial cell line, only p40 is present, whereas both variants appear together in eight tissues from fourth-instar larvae, although in somewhat different proportions. Furthermore, the appearance of the two isoforms was studied in relation to a specific 35,40 kb mRNA transcript in the salivary glands, the Balbiani ring mRNA. Because of their exceptional size, Balbiani ring messenger ribonucleoprotein particles in nucleoplasm and Balbiani ring polysomes in cytoplasm could be identified and selectively studied. We were able to establish that both isoforms are associated with both nuclear and cytoplasmic Balbiani ring mRNA. In addition, a p50-specific antibody coimmunoprecipitated p40 from Balbiani ring polysomes, suggesting that the two splicing isoforms are located along the same Balbiani ring mRNA molecule. The functional significance of the two isoforms is being discussed. [source] Distinct localizations and repression activities of MM-1 isoforms toward c-Myc,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2006Yuko Hagio Abstract MM-1 was identified as a c-Myc-binding protein and has been reported to repress the E-box-dependent transcription activity of c-Myc by recruiting HDAC1 complex via TIF1 ,/KAP1. In this study, originally isolated MM-1 was found to be a fusion protein comprised of the N-terminal 13 amino acids from the sequence of chromosome 14 and of the rest of the amino acids from that of chromosome 12 and was found to be expressed ubiquitously in all human tissues. Four splicing isoforms of MM-1, MM-1,, MM-1,, MM-1,, and MM-1,, which are derived from the sequence of chromosome 12, were then identified. Of these isoforms, MM-1,, MM-1,, and MM-1, were found to be expressed in tissue-specific manners and MM-1, was found to be expressed ubiquitously. Although all of the isoforms potentially possessed c-Myc- and TIF1,-binding activities, MM-1, and MM-1, were found to be mainly localized in the cytoplasm and MM-1, and MM-1, were found to be localized in the nucleus together with both c-Myc and TIF1,. Furthermore, when repression activities of MM-1 isoforms toward c-Myc transcription activity were examined by reporter gene assays in HeLa cells, MM-1,, MM-1,, and MM-1,, but not MM-1,, were found to repress transcription activity of c-Myc, and the degrees of repression by MM-1, and MM-1, were smaller than those by MM-1 and MM-1,. These results suggest that each MM-1 isoform distinctly regulates c-Myc transcription activity in respective tissues. J. Cell. Biochem. © 2005 Wiley-Liss, Inc. [source] Changes in expression of anti-apoptotic protein, cflip, in granulosa cells during follicular atresia in porcine ovariesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2005Fuko Matsuda-Minehata Follicular selection is performed in mammalian ovaries, as most follicles undergo atresia during follicular development and growth. Follicular regression is indicated to begin with granulosa cell apoptosis. To reveal the molecular mechanisms of the selection, we examined the changes in the levels of cellular-Flice like inhibitory protein (cFLIP) expression in porcine granulosa cells. cFLIP is the homologue of intracellular apoptosis inducer (procaspase-8/Flice), and has two alternative splicing isoforms: cFLIP short form (cFLIPS) and long form (cFLIPL). By competing with caspase-8, cFLIP inhibits apoptosis initiated by death receptors. The changes in the levels of cFLIPS and cFLIPL mRNA and protein expression in granulosa cells were determined by RT-PCR and Western blotting, respectively. cFLIPL mRNA and protein were highly expressed in granulosa cells of healthy follicles and decreased during atresia. cFLIPS mRNA levels in granulosa cells were low and showed no change among the stages of follicular development, and its protein level was extremely low. We examined the changes in the localization of cFLIP mRNAs in pig ovaries by in situ hybridization and found that cFLIPL is abundant in granulosa cells of healthy follicles in comparison with those of atretic follicles. Immunohistochemical analyses demonstrated that the cFLIP protein is highly expressed in the granulosa cell of healthy follicles but weakly expressed in that of atretic follicles. We presumed that cFLIP, especially cFLIPL, plays an anti-apoptotic role in the granulosa cells of healthy follicles of pig ovaries, and that cFLIP could be a major survival factor that determines whether growth or atresia occurs in porcine follicles. © 2005 Wiley-Liss, Inc. [source] ERK-regulated differential expression of the Mitf 6a/b splicing isoforms in melanomaPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2010Aline Primot Summary The master regulator of the melanocyte lineage Mitf is intimately involved in development as well as melanoma, controlling cell survival, differentiation, proliferation and metastasis/migration. Consistent with its central role, Mitf expression and Mitf post-translational modifications are tightly regulated. An additional potential level of regulation is afforded by differential splicing of Mitf exon-6 leading to the generation of two isoforms that differ by the presence of six amino-acids in the Mitf (+) isoform and which have differential effects on cell cycle progression. However, whether the ratio of the two isoforms is regulated and whether their expression correlates with melanoma progression is not known. Here, we show that the differential expression of the Mitf 6a/b isoforms is dependent on the MAPKinase signalling, being linked to the activation of MEK1-ERK2, but not to N-RAS/B-RAF mutation status. In addition, quantification of Mitf 6a/b splicing forms in 86 melanoma samples revealed substantially increased levels of the Mitf (,) form in a subset of metastatic melanomas. The results suggest that differential expression of the Mitf 6a/b isoforms may represent an additional mechanism for regulating Mitf function and melanoma biology. [source] | ||||||||||