RUNX family: Regulation and diversification of roles through interacting proteins

Abstract

The Runt-related transcription factors (RUNX) belong to an ancient family of metazoan genes involved in developmental processes. Through multiple protein-interacting partners, RUNX proteins have been implicated in diverse signaling pathways and cellular processes. The frequent inactivation of RUNX genes in cancer indicates crucial roles for RUNX in tumor suppression. This review discusses the abilities of RUNX proteins, in particular RUNX3, to integrate oncogenic signals or environmental cues and to initiate appropriate tumor suppressive responses.RUNX proteins are crucial transcription factors that regulate a wide range of biological processes to orchestrate proper cell fate determination. Traditionally described as a DNA-binding protein that binds CBFb (also known as PEBP2b) to form the heterodimeric core-binding factor (CBF) or polyomavirus enhancer-binding protein 2 (PEBP2) transcription complex, RUNX is now viewed as a multifaceted protein that associates with diverse proteins to direct biological outcomes in a context-dependent manner. 1 This review discusses how combinatorial interactions-dynamically regulated in a spatiotemporal manner-have endowed RUNX proteins with a plethora of functions, some seemingly opposite. Because of space constraints, emphasis will be placed on the tumor suppressive properties of RUNX3.RUNX proteins have been identified in many metazoans: most, if not all, play requisite roles in developmental processes. While primitive metazoans such as sea urchin and C. elegans appear to possess a single RUNX family member, multiple RUNX proteins have been identified in mammals, Drosophila and Fugu, 2 indicating (i) evolutionary conserved roles in metazoans and (ii) the necessity for elaborate and tight regulation of RUNX activity when specifying complex developmental events in higher organisms. In mammals, there are three RUNX family members: RUNX1, RUNX2 and RUNX3. Mouse models have shown that disruption of individual Runx genes resulted in distinct phenotypes, indicating nonredundant, tissue-specific roles: Runx1 knockout is associated with lack of definitive hematopoiesis; Runx2 knockout resulted in the absence of bone formation and Runx3 knockout led to mice with defects in cytotoxic T-cell development, as well as gastrointestinal (GI) and neural disorders. 3-5 During T-lymphocyte development, Runx3 involvement in the establishment of epigenetic silencing of CD4 is critical for lineage specification and homeostasis, and the absence of Runx3 is associated with defective cytotoxic T cells 6 ; in the intestine, heterozygous inactivation of Runx3 induced colon adenoma; in the gastric epithelia, Runx3 deficiency is associated with a precancerous state, distinctly characterized by loss of chief cells 7 and in the lung, Runx3 plays requisite roles during bronchiolar epithelial cell differentiation and tumor suppression. 8,9 All offer compelling evidence for a causal link between loss of Runx3, deregulated differentiation and preneoplasia. Together with the fact that Runx3-deficient mice are tu...

Biological Activities of RUNX1 Mutants Predict Secondary Acute Leukemia Transformation from Chronic Myelomonocytic Leukemia and Myelodysplastic Syndromes

“…Recently, Bresciani and colleagues reported that RUNX1 can drive the emergence of nascent hematopoietic stem cells without its heterodimeric partner CBFb (24), suggesting parts of RUNX1's biologic functions are independent of CBFb. In addition, lots of cellular proteins, Myb, Ets, ALY, TLE/Groucho, p300, CBP, YAP, SIN3A, MOZ, PML, PRMT1, TAL1, MLL, Shp2, SWI/SNF, etc., have been described to interact with RUNX1 (25). Of note, RUNX1 interacted with several transcriptional factors through a dynamic combinatorial mechanism to orchestrate hematopoietic differentiation (26,27).…”

Runx1 exon 6–related alternative splicing isoforms differentially regulate hematopoiesis in mice

“…It lacks several well-recognized regulatory domains in the C terminus. 18,38 These facts prompted us to do a cross-species comparison to examine evolutionary conservation of this isoform. We found that the homologous mouse sequence of human exon 7A lacked sequences relating to splice acceptor AG and stop codon TAA, indicating that there is no ortholog of human RUNX1a in mice ( Figure 1A-B).…”

TGFβ Promotes Genomic Instability after Loss of RUNX3

“…In earlier studies, it has been shown that RUNX2 binds and recruits CEBPd to promoter enabling transcription and precluding the requirement for direct DNA binding (46). Alternatively, since RUNX3 is known to establish multiple protein-interacting partners, it is possible that RUNX3 might control HMOX1 transcription indirectly through interaction with transcription factors known to regulate HMOX1 levels (47).…”