Alternative Promoter Usage at the Notch1 Locus Supports Ligand-Independent Signaling in T Cell Development and Leukemogenesis

Pablo Gomez-del Arco, Mariko Kashiwagi, Audrey F. Jackson, Taku Naito, Jiangwen Zhang, Feifei Liu, Barbara Kee, Marc Vooijs, Freddy Radtke, Juan Miguel Redondo, Katia Georgopoulos*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Loss of the transcription factor Ikaros is correlated with Notch receptor activation in T cell acute lymphoblastic leukemia (T-ALL). However, the mechanism remains unknown. We identified promoters in Notch1 that drove the expression of Notch1 proteins in the absence of a ligand. Ikaros bound to both canonical and alternative Notch1 promoters and its loss increased permissive chromatin, facilitating recruitment of transcription regulators. At early stages of leukemogenesis, increased basal expression from the canonical and 5'-alternative promoters initiated a feedback loop, augmenting Notch1 signaling. Ikaros also repressed intragenic promoters for ligand-independent Notch1 proteins that are cryptic in wild-type cells, poised in preleukemic cells, and active in leukemic cells. Only ligand-independent Notch1 isoforms were required for Ikaros-mediated leukemogenesis. Notch1 alternative-promoter usage was observed during T cell development and T-ALL progression. Thus, a network of epigenetic and transcriptional regulators controls conventional and unconventional Notch signaling during normal development and leukemogenesis.
Original languageEnglish
Pages (from-to)685-698
JournalImmunity
Volume33
Issue number5
DOIs
Publication statusPublished - 24 Nov 2010

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