This report describes a Drosophila model used to characterize the role CNOT3 and other components of the CCR4-NOT complex in the development of T-cell acute lymphoblastic leukemia (T-ALL) and other cancers. The fly model was developed when CNOT3 emerged as a candidate tumor suppressor gene in whole exome sequencing of (T-ALL) patients. The CCR4-NOT complex contributes to regulation of RNA metabolism at all steps, including transcription, mRNA stability, and eventual degradation in the cytoplasm. There is a single gene orthologous to CNOT3 in Drosophila, Dmel\Not3, for which RNAi targeting constructs and an allele caused by insertional mutagenesis have been generated.
Of the human CCR4-NOT complex genes, Hsap\CNOT1 and Hsap\CNOT7 have been introduced into flies. Hsap\CNOT1 has been characterized in the context of a neurodevelopmental disorder, Vissers-Bodmer syndrome (FBhh0001252). An Hsap\CNOT7 stock is available, but has not been characterized.
Like all invertebrates, flies lack cells analogous to the hematopoietic lymphoid lineage. However, based on the knowledge that activating mutations of NOTCH1 are frequently associated with T-ALL, a fly model in which the Notch ligand Dl is overexpressed in the developing eyes was used as a sensitized system to characterize the impact of Dmel\Not3 mutations. This emulates the multi-step progression of most cancers, including ALL. Dl overexpression in eyes results in slightly enlarged but otherwise normal-appearing eyes. Dl overexpression combined with knockdown of Not3, effected by RNAi, results in dramatic hyperproliferative eye phenotypes.
Other subunits of the Drosophila CCR4-NOT complex have been tested in this system. Reduction in expression of Not1 (orthologous to human CNOT1), Rga (orthologous to CNOT2), or Pop2 (orthologous to CNOT7 and CNOT8) in combination with Dl overexpression results in hyperproliferative eye phenotypes. Reduction in expression of twin (orthologous to CNOT6 and CNOT6L) in combination with Dl overexpression results in metastatic, as well as hyperproliferative, phenotypes. Physical and genetic interactions have been described for these fly genes; see below and in the respective gene reports.
See also the FlyBase gene group report CCR4-NOT COMPLEX (FBgg0000469) and the human disease model report 'cancer, multiple, Notch signaling pathway' (FBhh0000766).
[updated Jun. 2022 by FlyBase; FBrf0222196]
T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive type of blood cancer that accounts for about 15% of pediatric and 25% of adult acute lymphoblastic leukemia (ALL) cases. It is considered as a paradigm for the multistep nature of cancer initiation and progression (Durinck et al., 2015; pubmed:26123366).
Activating mutations in NOTCH1 are found in a large percentage of human T-ALL cases (Grabher et al., 2006; pubmed:16612405).
The CCR4-NOT complex is a multisubunit protein complex that is conserved in all eukaryotes and contributes to regulation of RNA metabolism at all steps, from synthesis to degradation in the cytoplasm (Collart, 2016; pubmed:26821858).
One to one: 1 human to 1 Drosophila.
Moderate-scoring ortholog of human CNOT3 (1 Drosophila to 1 human). Dmel\Not3 shares 40% identity and 54% similarity with the human gene.
High-scoring ortholog of human CNOT6 and CNOT6L (1 Drosophila to 2 human). Dmel\twin shares 57% identity and 72-73% similarity with the human genes.
High-scoring ortholog of human CNOT1 (1 Drosophila to 1 human). Dmel\Not1 shares 46% identity and 62% similarity with the human gene.
High-scoring ortholog of human CNOT8 and CNOT7 (1 Drosophila to 2 human). Dmel\Pop2 shares 68% identity and 84% similarity with CNOT8; it shares 56% identity and 68% similarity with CNOT7.
Moderate- to high-scoring ortholog of human DLL1 and DLL4 (1 Drosophila to 2 human); additional less closely related genes in human. Dmel\Dl shares 39% identity and 51-53% similarity with human DLL1 and DLL4.
