title: Notch3 and the Notch3-upregulated RNA-binding protein HuD regulate Ikaros alternative splicing.
abstract: Constitutive activation of the transmembrane receptor, Notch3, and loss of function of the hematopoietic transcription repressor, Ikaros (IK), play direct roles in T-cell differentiation and leukemogenesis that are dependent on pre-T-cell receptor (pre-TCR) signaling. We demonstrate the occurrence of crosstalk between Notch3 and IK that results in transcriptional regulation of the gene encoding the pTalpha chain of the pre-TCR. We also show that, in the presence of the pre-TCR, constitutive activation of Notch3 in thymocytes causes increased expression of dominantnegative non-DNA-binding IK isoforms, which are able to restrain the IK inhibition of Notch3's transcriptional activation of pTalpha. This effect appears to be mediated by Notch3's pre-TCR-dependent upregulation of the RNA-binding protein, HuD. Notch3 signaling thus appears to play a critical role in the diminished IK activity described in several lymphoid leukemias. By exerting transcription-activating and transcription-repressing effects on the pTalpha promoter, Notch3 and IK cooperate in the fine-tuning of pre-TCR expression and function, which has important implications for the regulation of thymocyte differentiation and proliferation.
authors.affiliation: Department of Experimental Medicine, University 'La Sapienza', Roma, Italy.
authors.forename: Diana
authors.initials: D
authors.lastname: Bellavia
authors.forename: Marco
authors.initials: M
authors.lastname: Mecarozzi
authors.forename: Antonio F
authors.initials: AF
authors.lastname: Campese
authors.forename: Paola
authors.initials: P
authors.lastname: Grazioli
authors.forename: Claudio
authors.initials: C
authors.lastname: Talora
authors.forename: Luigi
authors.initials: L
authors.lastname: Frati
authors.forename: Alberto
authors.initials: A
authors.lastname: Gulino
authors.forename: Isabella
authors.initials: I
authors.lastname: Screpanti
mesh_terms: D017398:Alternative Splicing / Q000235:genetics / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers; D051959:ELAV Proteins / Q000378:metabolism*; D000067779:ELAV-Like Protein 4; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology*; D051740:Ikaros Transcription Factor / Q000235:genetics / Q000502:physiology*; D008156:Luciferases; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D034622:RNA Interference; D000071656:Receptor, Notch3; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013601:T-Lymphocytes / Q000166:cytology* / Q000378:metabolism
chemical_list: D017931:DNA Primers; D051959:ELAV Proteins; D000067779:ELAV-Like Protein 4; C498011:Elavl4 protein, mouse; D008562:Membrane Glycoproteins; C499373:Notch3 protein, mouse; D000071656:Receptor, Notch3; D016693:Receptors, Antigen, T-Cell, alpha-beta; D051880:Receptors, Notch; C497238:Zfpn1a1 protein, mouse; C090377:pre-T cell receptor alpha; D051740:Ikaros Transcription Factor; D008156:Luciferases