title: Haploinsufficiency of the c-myc transcriptional repressor FIR, as a dominant negative-alternative splicing model, promoted p53-dependent T-cell acute lymphoblastic leukemia progression by activating Notch1.
abstract: FUSE-binding protein (FBP)-interacting repressor (FIR) is a c-myc transcriptional suppressor. A splice variant of FIR that lacks exon 2 in the transcriptional repressor domain (FIRΔexon2) upregulates c-myc transcription by inactivating wild-type FIR. The ratio of FIRΔexon2/FIR mRNA was increased in human colorectal cancer and hepatocellular carcinoma tissues. Because FIRΔexon2 is considered to be a dominant negative regulator of FIR, FIR heterozygous knockout (FIR⁺/⁻) C57BL6 mice were generated. FIR complete knockout (FIR⁻/⁻) was embryonic lethal before E9.5; therefore, it is essential for embryogenesis. This strongly suggests that insufficiency of FIR is crucial for carcinogenesis. FIR⁺/⁻ mice exhibited prominent c-myc mRNA upregulation, particularly in the peripheral blood (PB), without any significant pathogenic phenotype. Furthermore, elevated FIRΔexon2/FIR mRNA expression was detected in human leukemia samples and cell lines. Because the single knockout of TP53 generates thymic lymphoma, FIR⁺/⁻TP53⁻/⁻ generated T-cell type acute lymphocytic/lymphoblastic leukemia (T-ALL) with increased organ or bone marrow invasion with poor prognosis. RNA-sequencing analysis of sorted thymic lymphoma cells revealed that the Notch signaling pathway was activated significantly in FIR⁺/⁻TP53⁻/⁻ compared with that in FIR⁺/⁺TP53⁻/⁻ mice. Notch1 mRNA expression in sorted thymic lymphoma cells was confirmed using qRT-PCR. In addition, flow cytometry revealed that c-myc mRNA was negatively correlated with FIR but positively correlated with Notch1 in sorted T-ALL/thymic lymphoma cells. Moreover, the knockdown of TP53 or c-myc using siRNA decreased Notch1 expression in cancer cells. In addition, an adenovirus vector encoding FIRΔexon2 cDNA increased bleomycin-induced DNA damage. Taken together, these data suggest that the altered expression of FIRΔexon2 increased Notch1 at least partially by activating c-Myc via a TP53-independent pathway. In conclusion, the alternative splicing of FIR, which generates FIRΔexon2, may contribute to both colorectal carcinogenesis and leukemogenesis.
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.|Division of Laboratory Medicine, Chiba University Hospital, Inohana, Chiba, Japan.
authors: Kazuyuki
authors: K
authors: Matsushita
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.|Division of Laboratory Medicine, Chiba University Hospital, Inohana, Chiba, Japan.
authors: Kouichi
authors: K
authors: Kitamura
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Bahityar
authors: B
authors: Rahmutulla
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Nobuko
authors: N
authors: Tanaka
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.|Division of Laboratory Medicine, Chiba University Hospital, Inohana, Chiba, Japan.
authors: Takayuki
authors: T
authors: Ishige
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Mamoru
authors: M
authors: Satoh
authors: Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana, Chiba, Japan.
authors: Tyuji
authors: T
authors: Hoshino
authors: Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, Inohana, Chuo-ku, Chiba, Japan.
authors: Satoru
authors: S
authors: Miyagi
authors: Department of Pediatrics, Graduate School of Medicine, Kobe University, Kusunoki-cho, Kobe, Japan.
authors: Takeshi
authors: T
authors: Mori
authors: Division of Laboratory Medicine, Chiba University Hospital, Inohana, Chiba, Japan.
authors: Sakae
authors: S
authors: Itoga
authors: Department of Surgery, School of Medicine, Toho University, Omori-nishi, Ota-ku, Tokyo, Japan.
authors: Hideaki
authors: H
authors: Shimada
authors: Laboratory of Proteome Research, National Institute of Biomedical Innovation, Saito-Asagi, Ibaraki, Osaka, Japan.
authors: Takeshi
authors: T
authors: Tomonaga
authors: Oriental Yeast Co., Ltd. Azusawa, Itabashi-ku, Tokyo, Japan.
authors: Minoru
authors: M
authors: Kito
authors: Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, Inohana, Chuo-ku, Chiba, Japan.
authors: Yaeko
authors: Y
authors: Nakajima-Takagi
authors: Department of Genetics, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Hyogo Prefecture, Japan.
authors: Shuji
authors: S
authors: Kubo
authors: Department of Haematology, Chiba University Hospital, Inohana, Chiba, Japan.
authors: Chiaki
authors: C
authors: Nakaseko
authors: Department of Biomedical Science, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Masahiko
authors: M
authors: Hatano
authors: Department of Medical Physiology, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Takashi
authors: T
authors: Miki
authors: Department of Pediatrics, Graduate School of Medicine, Kobe University, Kusunoki-cho, Kobe, Japan.|Department of Medical Rehabilitation, Faculty of Rehabilitation, Kobegakuin University, Arise, Ikawadani, Nishi, Kobe, Japan.
authors: Masafumi
authors: M
authors: Matsuo
authors: Department of Molecular Oncology, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Masaki
authors: M
authors: Fukuyo
authors: Department of Molecular Oncology, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.
authors: Atsushi
authors: A
authors: Kaneda
authors: Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, Inohana, Chuo-ku, Chiba, Japan.
authors: Atsushi
authors: A
authors: Iwama
authors: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Inohana, Chiba, Japan.|Division of Laboratory Medicine, Chiba University Hospital, Inohana, Chiba, Japan.
authors: Fumio
authors: F
authors: Nomura
mesh_terms: D000328:Adult; D017398:Alternative Splicing; D000818:Animals; D018450:Disease Progression; D005260:Female; D057895:Haploinsufficiency; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D051881:Receptor, Notch1 / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D051881:Receptor, Notch1; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; C410595:poly-U binding splicing factor 60KDa
keywords: FBP interacting repressor (FIR); P53; T-ALL; haplo-insufficiency; leukemia; splicing variant