Delayed Mesoderm and Erythroid Differentiation of Murine Embryonic Stem Cells in the Absence of the Transcriptional Regulator FUBP1

FUBP1 in human cancer: Characteristics, functions, and potential applications

Far upstream element-binding protein 1 (FUBP1) is a single-stranded nucleic acid-binding protein that binds to the Far Upstream Element (FUSE) sequence and is involved in important biological processes, including DNA transcription, RNA biogenesis, and translation. Recent studies have highlighted the significance of aberrant expression or mutations in FUBP1 in the development of various tumors, with FUBP1 overexpression often indicating oncogenic roles in different tumor types. However, it is worth noting that recent research has discovered its tumor-suppressive role in cancer, which is not yet fully understood and appears to be tissue- or context-dependent. This review summarizes the association between FUBP1 and diverse cancers and discusses the functions of FUBP1 in cancer. In addition, this review proposes potential clinical implications and outlines future research directions to pave the way for the development of targeted therapeutic strategies focusing on FUBP1.

FUBP1 promotes colorectal cancer stemness and metastasis via DVL1-mediated activation of Wnt/β-catenin signaling

Distant metastasis is, unfortunately, the leading cause of death in colorectal cancer (CRC). Approximately 50% of CRC patients develop liver metastases, while 10–30% of patients develop pulmonary metastases. The occurrence of metastasis is considered to be almost exclusively driven by cancer stem cells (CSCs) formation. However, the key molecules that confer the transformation to stem cells in CRC, and subsequent metastasis, remain unclear. Far upstream element‐binding protein 1 (FUBP1), a transcriptional regulator of c‐Myc, was screened in CSCs of CRC by mass spectrometry and was examined by immunohistochemistry in a cohort of CRC tissues. FUBP1 was upregulated in 85% of KRAS‐mutant and 25% of wild‐type CRC patients. Further, whether in KRAS‐mutant or wild‐type patients, elevated FUBP1 was positively correlated with CRC lymph node metastasis and clinical stage, and negatively associated with overall survival. Overexpression of FUBP1 significantly enhanced CRC cell migration, invasion, tumor sphere formation, and CD133 and ALDH1 expression in vitro, and tumorigenicity in vivo. Mechanistically, FUBP1 promoted the initiation of CSCs by activating Wnt/β‐catenin signaling via directly binding to the promoter of DVL1, a potent activator of β‐catenin. Knockdown of DVL1 significantly inhibited the transformation to stem cells in, as well as the tumorigenicity of, CRC. Activation of Wnt/β‐catenin signaling by DVL1 increased pluripotent transcription factors, including c‐Myc, NANOG, and SOX2. Moreover, FUBP1 was upregulated at the post‐transcriptional level. Elevated FUBP1 levels in KRAS wild‐type CRC patients is due to the decrease in Smurf2, which promotes ubiquitin‐mediated degradation of FUBP1. In contrast, FUBP1 was upregulated in KRAS‐mutant patients through both inhibition of caspase 3‐dependent cleavage and decreased Smurf2. Our results demonstrate, for the first time, that FUBP1 is an oncogene, initiating the development of CSCs, as well as a new powerful endogenous Wnt‐signaling agonist that could provide an important prognostic factor and therapeutic target for metastasis in both KRAS‐mutant and wild‐type CRC.

FUSE binding protein 1 (FUBP1) expression is upregulated by T-cell acute lymphocytic leukemia protein 1 (TAL1) and required for efficient erythroid differentiation

During erythropoiesis, haematopoietic stem cells (HSCs) differentiate in successive steps of commitment and specification to mature erythrocytes. This differentiation process is controlled by transcription factors that establish stage- and cell type-specific gene expression. In this study, we demonstrate that FUSE binding protein 1 (FUBP1), a transcriptional regulator important for HSC self-renewal and survival, is regulated by T-cell acute lymphocytic leukaemia 1 (TAL1) in erythroid progenitor cells. TAL1 directly activates the FUBP1 promoter, leading to increased FUBP1 expression during erythroid differentiation. The binding of TAL1 to the FUBP1 promoter is highly dependent on an intact GATA sequence in a combined E-box/GATA motif. We found that FUBP1 expression is required for efficient erythropoiesis, as FUBP1-deficient progenitor cells were limited in their potential of erythroid differentiation. Thus, the finding of an interconnection between GATA1/TAL1 and FUBP1 reveals a molecular mechanism that is part of the switch from progenitor- to erythrocyte-specific gene expression. In summary, we identified a TAL1/FUBP1 transcriptional relationship, whose physiological function in haematopoiesis is connected to proper erythropoiesis.

The master regulator FUBP1: its emerging role in normal cell function and malignant development

The human Far Upstream Element (FUSE) Binding Protein 1 (FUBP1) is a multifunctional DNA- and RNA-binding protein involved in diverse cellular processes. FUBP1 is a master regulator of transcription, translation, and RNA splicing. FUBP1 has been identified as a potent pro-proliferative and anti-apoptotic factor by modulation of complex networks. FUBP1 is also described either as an oncoprotein or a tumor suppressor. Especially, FUBP1 overexpression is observed in a growing number of cancer and leads to a deregulation of targets that includes the fine-tuned MYC oncogene. Moreover, recent loss-of-function analyses of FUBP1 establish its essential functions in hematopoietic stem cell maintenance and survival. Therefore, FUBP1 appears as an emerging suspect in hematologic disorders in addition to solid tumors. The scope of the present review is to describe the advances in our understanding of the molecular basis of FUBP1 functions in normal cells and carcinogenesis. We also delineate the recent progresses in the understanding of the master role of FUBP1 in normal and pathological hematopoiesis. We conclude that FUBP1 is not only worth studying biologically but is also of clinical relevance through its pivotal role in regulating multiple cellular processes and its involvement in oncogenesis.

Far Upstream Element-Binding Protein 1 Regulates LSD1 Alternative Splicing to Promote Terminal Differentiation of Neural Progenitors

Loss of a cell's ability to terminally differentiate because of mutations is a selected genetic event in tumorigenesis. Genomic analyses of low-grade glioma have reported recurrent mutations of far upstream element-binding protein 1 (FUBP1). Here, we show that FUBP1 expression is dynamically regulated during neurogenesis and that its downregulation in neural progenitors impairs terminal differentiation and promotes tumorigenesis collaboratively with expression of IDH1R132H. Mechanistically, collaborative action between SRRM4 and FUBP1 is necessary for mini-exon splicing of the neurospecific LSD1+8a isoform. LSD1+8a was downregulated upon loss of FUBP1 in neural progenitors, thereby impairing terminal neuronal differentiation and maturation. Reinforcing LSD1+8a expression in FUBP1-downregulated neural progenitors restored terminal differentiation and suppressed tumorigenesis; hence, LSD1+8a is an obligatory effector of FUBP1-dependent neuronal differentiation. These findings establish a direct role for FUBP1 in neuronal differentiation and also explain its tumor-suppressor function in the nervous system.