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Identification of genes induced by NOTCH1 in a chronic lymphocytic leukaemia (CLL) cell line and tracking of these genes in primary CLL patients

ABSTRACT: NOTCH1 is mutationally activated in ~15% of cases of chronic lymphocytic leukaemia (CLL), but its role in B-cell development and leukemogenesis is not known. Here, we report that the active intracellular portion of NOTCH1 (ICN1) is detectable in ~50% of peripheral blood CLL cases lacking gene mutations. We identify a ‘NOTCH1 CLL gene expression signature’ in CLL cells, and show that this signature is significantly enriched in primary CLL cases expressing ICN1, independent of NOTCH1 mutation. NOTCH1 target genes include key regulators of B-cell proliferation, survival and signal transduction physiology. In particular, we show that MYC is a direct target of NOTCH1 via B-cell specific distal regulatory elements, thus implicating this oncogene in the pathogenesis of the disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE92626 | GEO | 2017/03/24

SECONDARY ACCESSION(S): PRJNA358194

REPOSITORIES: GEO

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Project description:Cyclin C was cloned as a growth-promoting G1 cyclin1,2, and several studies postulated a role for cyclin C in driving cell proliferation3-8 . Moreover, cyclin C, together with its kinase partner, the cyclin-dependent kinase CDK8, is believed to represent an essential component of basal transcriptional machinery where it globally represses gene expression9-13. However, the function of cyclin C in vivo has never been addressed. Here we show that in the living organism cyclin C acts as a haploinsufficient tumor suppressor, through its function of controlling Notch1 oncogene levels. Cyclin C activates an “orphan” CDK19 kinase14, as well as CDK8 and CDK3. These cyclin C-CDK complexes phosphorylate Notch1 intracellular domain (ICN1), which allows binding of ICN1 to Fbw7 and triggers ICN1 polyubiquitination. Genetic ablation of cyclin C blocks ICN1 phosphorylation, disrupts Fbw7 binding, and decreases ICN1 ubiquitination in vivo, thereby strongly elevating ICN1 levels in several compartments of cyclin C knockout mice. Cyclin C was cloned as a growth-promoting G1 cyclin1,2, and several studies postulated a role for cyclin C in driving cell proliferation3-8 . Moreover, cyclin C, together with its kinase partner, the cyclin-dependent kinase CDK8, is believed to represent an essential component of basal transcriptional machinery where it globally represses gene expression9-13. However, the function of cyclin C in vivo has never been addressed. Here we show that in the living organism cyclin C acts as a haploinsufficient tumor suppressor, through its function of controlling Notch1 oncogene levels. Cyclin C activates an “orphan” CDK19 kinase14, as well as CDK8 and CDK3. These cyclin C-CDK complexes phosphorylate Notch1 intracellular domain (ICN1), which allows binding of ICN1 to Fbw7 and triggers ICN1 polyubiquitination. Genetic ablation of cyclin C blocks ICN1 phosphorylation, disrupts Fbw7 binding, and decreases ICN1 ubiquitination in vivo, thereby strongly elevating ICN1 levels in several compartments of cyclin C knockout mice.

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Identification of genes induced by NOTCH1 in a chronic lymphocytic leukaemia (CLL) cell line and tracking of these genes in primary CLL patients

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