hMOB3 modulates MST1 apoptotic signaling and supports tumor growth in glioblastoma multiforme

Mapping the MOB proteins' proximity network reveals a unique interaction between human MOB3C and the RNase P complex

Distinct functions mediated by members of the monopolar spindle-one-binder (MOB) family of proteins remain elusive beyond the evolutionarily conserved and well-established roles of MOB1 (MOB1A/B) in regulating tissue homeostasis within the Hippo pathway. Since MOB proteins are adaptors, understanding how they engage in protein-protein interactions and help assemble complexes is essential to define the full scope of their biological functions. To address this, we undertook a proximity-dependent biotin identification approach to define the interactomes of all seven human MOB proteins in HeLa and human embryonic kidney 293 cell lines. We uncovered >200 interactions, of which at least 70% are unreported on BioGrid. The generated dataset reliably recalled the bona fide interactors of the well-studied MOBs. We further defined the common and differential interactome between different MOBs on a subfamily and an individual level. We discovered a unique association between MOB3C and 7 of 10 protein subunits of the RNase P complex, an endonuclease that catalyzes tRNA 5' maturation. As a proof of principle for the robustness of the generated dataset, we validated the specific interaction of MOB3C with catalytically active RNase P by using affinity purification-mass spectrometry and pre-tRNA cleavage assays of MOB3C pulldowns. In summary, our data provide novel insights into the biology of MOB proteins and reveal the first interactors of MOB3C, components of the RNase P complex, and hence an exciting nexus with RNA biology.

MOB3A Bypasses BRAF and RAS Oncogene-Induced Senescence by Engaging the Hippo Pathway

Oncogenic activation of the RTK-RAS-RAF-MEK-ERK pathway occurs in approximately 25% of all human cancers, yet activated RAS, BRAF, or MEK expression in primary cells leads to a prolonged and predominantly irreversible cell-cycle arrest termed oncogene-induced senescence (OIS). OIS acts as an intrinsic tumor suppressor mechanism, serving as a barrier to tumor progression. Screening a library of activated kinases and kinase-regulatory proteins we identified MOB3A, a Mps-one binder coactivator (MOB) protein family member, whose constitutive expression permits proliferation and suppresses senescence in response to oncogenic RAS and BRAF signals. MOB3A is one of seven human MOB genes, which are highly conserved from yeast to human and that function to activate the Hippo pathway kinases (MST/LATS) or NDR kinases through direct association. Here we show that within the MOB family of genes MOB3A and C are unique in their ability to allow primary cell proliferation in the face of sustained oncogene signaling. Unlike the canonical MOB1A/B proteins, MOB3A inhibits Hippo/MST/LATS signaling and constitutive MOB3A membrane localization phenocopies OIS bypass seen with elevated YAP expression. Moreover, inhibition of MOB3 family member expression results in decreased proliferation and tumor growth of cancer cell lines. Together these data identify MOB3A's role in bypass of oncogene induced senescence and its role as a Hippo pathway inhibitor.

IMPLICATIONS

These results suggest that MOB3 targeting to re-engage the Hippo pathway, or direct targeting of YAP/TAZ, may be viable therapeutic strategies potential for RAS-pathway driven tumours.

Hippo Signaling Pathway in Gliomas

The Hippo signaling pathway is a highly conserved pathway involved in tissue development and regeneration that controls organ size through the regulation of cell proliferation and apoptosis. The core Hippo pathway is composed of a block of kinases, MST1/2 (Mammalian STE20-like protein kinase 1/2) and LATS1/2 (Large tumor suppressor 1/2), which inhibits nuclear translocation of YAP/TAZ (Yes-Associated Protein 1/Transcriptional co-activator with PDZ-binding motif) and its downstream association with the TEAD (TEA domain) family of transcription factors. This pathway was recently shown to be involved in tumorigenesis and metastasis in several cancers such as lung, breast, or colorectal cancers but is still poorly investigated in brain tumors. Gliomas are the most common and the most lethal primary brain tumors representing about 80% of malignant central nervous system neoplasms. Despite intensive clinical protocol, the prognosis for patients remains very poor due to systematic relapse and treatment failure. Growing evidence demonstrating the role of Hippo signaling in cancer biology and the lack of efficient treatments for malignant gliomas support the idea that this pathway could represent a potential target paving the way for alternative therapeutics. Based on recent advances in the Hippo pathway deciphering, the main goal of this review is to highlight the role of this pathway in gliomas by a state-of-the-art synthesis.

Predicting chemosensitivity using drug perturbed gene dynamics

Background

One of the current directions of precision medicine is the use of computational methods to aid in the diagnosis, prognosis, and treatment of disease based on data driven approaches. For instance, in oncology, there has been a particular focus on development of algorithms and biomarkers that can be used for pre-clinical and clinical applications. In particular large-scale omics-based models to predict drug sensitivity in in vitro cancer cell line panels have been used to explore the utility and aid in the development of these models as clinical tools. Additionally, a number of web-based interfaces have been constructed for researchers to explore the potential of drug perturbed gene expression as biomarkers including the NCI Transcriptional Pharmacodynamic Workbench. In this paper we explore the influence of drug perturbed gene dynamics of the NCI Transcriptional Pharmacodynamics Workbench in computational models to predict in vitro drug sensitivity for 15 drugs on the NCI60 cell line panel.

Results

This work presents three main findings. First, our models show that gene expression profiles that capture changes in gene expression after 24 h of exposure to a high concentration of drug generates the most accurate predictive models compared to the expression profiles under different dosing conditions. Second, signatures of 100 genes are developed for different gene expression profiles; furthermore, when the gene signatures are applied across gene expression profiles model performance is substantially decreased when gene signatures developed using changes in gene expression are applied to non-drugged gene expression. Lastly, we show that the gene interaction networks developed on these signatures show different network topologies and can be used to inform selection of cancer relevant genes.

Conclusion

Our models suggest that perturbed gene signatures are predictive of drug response, but cannot be applied to predict drug response using unperturbed gene expression. Furthermore, additional drug perturbed gene expression measurements in in vitro cell lines could generate more predictive models; but, more importantly be used in conjunction with computational methods to discover important drug disease relationships.

MOB: Pivotal Conserved Proteins in Cytokinesis, Cell Architecture and Tissue Homeostasis

The MOB family proteins are constituted by highly conserved eukaryote kinase signal adaptors that are often essential both for cell and organism survival. Historically, MOB family proteins have been described as kinase activators participating in Hippo and Mitotic Exit Network/ Septation Initiation Network (MEN/SIN) signaling pathways that have central roles in regulating cytokinesis, cell polarity, cell proliferation and cell fate to control organ growth and regeneration. In metazoans, MOB proteins act as central signal adaptors of the core kinase module MST1/2, LATS1/2, and NDR1/2 kinases that phosphorylate the YAP/TAZ transcriptional co-activators, effectors of the Hippo signaling pathway. More recently, MOBs have been shown to also have non-kinase partners and to be involved in cilia biology, indicating that its activity and regulation is more diverse than expected. In this review, we explore the possible ancestral role of MEN/SIN pathways on the built-in nature of a more complex and functionally expanded Hippo pathway, by focusing on the most conserved components of these pathways, the MOB proteins. We discuss the current knowledge of MOBs-regulated signaling, with emphasis on its evolutionary history and role in morphogenesis, cytokinesis, and cell polarity from unicellular to multicellular organisms.

The cross-talk between the Hippo signaling pathway and autophagy:implications on physiology and cancer

Organ development is precisely guided by spatiotemporal cross-talks between a variety of signaling pathways regulating cell differentiation, proliferation, growth arrest and physiological cell death. Aberrant signaling inputs invariably lead to tissue dysfunction and to certain conditions, even malignant transformation. In this review, we focus on the functional interplay between the Hippo signaling pathway and autophagy in normal tissue homeostasis and in malignant tumor progression. Mounting experimental evidence for the regulation of cancer cell malignancy and therapy resistance by the functional cross-talk between Hippo signaling and autophagy highlights this signaling axis as a suitable therapeutic target to combat cancer.

Function of the MOB kinase activator-like 1 in the innate immune defense of the oriental river prawn (Macrobrachium nipponense)

The monopolar spindle one binder (MOB) protein, a key signal transducer of the Hippo signaling pathway, is involved in growth control and cancer. In this study, a new MOB kinase activator-like 1 of the oriental river prawns, Macrobrachium nipponense, (MnMOB1) was isolated and characterized. The open reading frame of MnMOB1 consisted of 651 nucleotides that encoded 216 amino acid residues and contained the Mob1_phocein domain. Phylogenetic analysis revealed that MnMOB1 clustered together with the MOB1 from Penaeus vannamei. The distribution of MnMOB1 expression in various tissues of normal prawn revealed that the MnMOB1 expression was highest in the hepatopancreas followed by those in the intestines, gill, heart, stomach, and hemocytes. In prawns challenged with Staphylococcus aureus and Vibrio parahaemolyticus, the expression levels of MnMOB1 in the hepatopancreas, gills, and intestine were upregulated. Furthermore, the expression levels of crustins and anti-lipopolysaccharide factors in prawn injected with S. aureus and V. parahaemolyticus and MnMOB1 knockdown were significantly decreased relative to those in the control group. These findings indicated that MnMOB1 is involved in the regulation of antimicrobial peptide expression and plays a crucial role in the innate immunity of M. nipponense.

Cullin-7 (CUL7) is overexpressed in glioma cells and promotes tumorigenesis via NF-κB activation

BACKGROUND

Cullin-7 (CUL7) is a member of the DOC domain-containing cullin family and is involved in the regulation of cell transformation. However, the clinical significance, potential mechanism and upstream regulators of CUL7 in malignant gliomas remain to be determined.

METHODS

Expression level data and clinical information were obtained via the Cancer Genome Atlas (TCGA) database, the Chinese Glioma Genome Atlas (CGGA) database, immunohistochemistry (IHC) and western blot analysis. Gene set enrichment analysis (GSEA) was used to explore the potential molecular mechanisms of CUL7. RNA silencing was performed using siRNA or lentiviral constructs in U87MG and U251 glioma cell lines and GSC267 glioma stem cells. CUL7 overexpression was performed using the GV141-CUL7 plasmid construct. In addition, overexpression of miR-3940-5p was performed and validated by quantitative real-time PCR (qRT-PCR). Cells were characterized in vitro or in vivo to evaluate their molecular status, cell proliferation, invasion, and migration by Cell Counting Kit (CCK)-8, EdU, flow cytometry, colony formation, Transwell and 3D tumour spheroid invasion assays. Coimmunoprecipitation (co-IP) and western blotting were performed to test the mechanisms of activation of the NF-κB signalling pathway.

RESULTS

High CUL7 expression was associated with a high tumour grade, a mesenchymal molecular glioma subtype and a poor prognosis in patients. Gene silencing of CUL7 in U87MG and U251 cells significantly inhibited tumour growth, invasion and migration in vitro and in vivo. Western blot analysis revealed that cyclin-dependent kinase inhibitors and epithelial-mesenchymal transition (EMT) molecular markers changed under CUL7 silencing conditions. In contrast, CUL7 overexpression promoted tumour growth, invasion and migration. Gene set enrichment analysis (GSEA) and western blot analysis revealed that CUL7 was positively associated with the NF-κB pathway. Moreover, with coimmunoprecipitation assays, we discovered that CUL7 physically associated with MST1, which further led to ubiquitin-mediated MST1 protein degradation, which promoted activation of the NF-κB signalling pathway. Finally, CUL7 was found to be downregulated by miR-3940-5p, which suppressed the development of gliomas.

CONCLUSIONS

Our findings indicate that CUL7 plays a significant role in promoting tumorigenesis via NF-κB activation and that it can be negatively regulated by miR-3940-5p in human gliomas. Furthermore, CUL7 might be a candidate molecular target for the treatment of glioma.

Mob Family Proteins: Regulatory Partners in Hippo and Hippo-Like Intracellular Signaling Pathways

Studies in yeast first delineated the function of Mob proteins in kinase pathways that regulate cell division and shape; in multicellular eukaryotes Mobs regulate tissue growth and morphogenesis. In animals, Mobs are adaptors in Hippo signaling, an intracellular signal-transduction pathway that restricts growth, impacting the development and homeostasis of animal organs. Central to Hippo signaling are the Nuclear Dbf2-Related (NDR) kinases, Warts and LATS1 and LATS2, in flies and mammals, respectively. A second Hippo-like signaling pathway has been uncovered in animals, which regulates cell and tissue morphogenesis. Central to this emergent pathway are the NDR kinases, Tricornered, STK38, and STK38L. In Hippo signaling, NDR kinase activation is controlled by three activating interactions with a conserved set of proteins. This review focuses on one co-activator family, the highly conserved, non-catalytic Mps1-binder-related (Mob) proteins. In this context, Mobs are allosteric activators of NDR kinases and adaptors that contribute to assembly of multiprotein NDR kinase activation complexes. In multicellular eukaryotes, the Mob family has expanded relative to model unicellular yeasts; accumulating evidence points to Mob functional diversification. A striking example comes from the most sequence-divergent class of Mobs, which are components of the highly conserved Striatin Interacting Phosphatase and Kinase (STRIPAK) complex, that antagonizes Hippo signaling. Mobs stand out for their potential to modulate the output from Hippo and Hippo-like kinases, through their roles both in activating NDR kinases and in antagonizing upstream Hippo or Hippo-like kinase activity. These opposing Mob functions suggest that they coordinate the relative activities of the Tricornered/STK38/STK38L and Warts/LATS kinases, and thus have potential to assemble nodes for pathway signaling output. We survey the different facets of Mob-dependent regulation of Hippo and Hippo-like signaling and highlight open questions that hinge on unresolved aspects of Mob functions.

Mob Family Proteins: Regulatory Partners in Hippo and Hippo-Like Intracellular Signaling Pathways

Studies in yeast first delineated the function of Mob proteins in kinase pathways that regulate cell division and shape; in multicellular eukaryotes Mobs regulate tissue growth and morphogenesis. In animals, Mobs are adaptors in Hippo signaling, an intracellular signal-transduction pathway that restricts growth, impacting the development and homeostasis of animal organs. Central to Hippo signaling are the Nuclear Dbf2-Related (NDR) kinases, Warts and LATS1 and LATS2, in flies and mammals, respectively. A second Hippo-like signaling pathway has been uncovered in animals, which regulates cell and tissue morphogenesis. Central to this emergent pathway are the NDR kinases, Tricornered, STK38, and STK38L. In Hippo signaling, NDR kinase activation is controlled by three activating interactions with a conserved set of proteins. This review focuses on one co-activator family, the highly conserved, non-catalytic Mps1-binder-related (Mob) proteins. In this context, Mobs are allosteric activators of NDR kinases and adaptors that contribute to assembly of multiprotein NDR kinase activation complexes. In multicellular eukaryotes, the Mob family has expanded relative to model unicellular yeasts; accumulating evidence points to Mob functional diversification. A striking example comes from the most sequence-divergent class of Mobs, which are components of the highly conserved Striatin Interacting Phosphatase and Kinase (STRIPAK) complex, that antagonizes Hippo signaling. Mobs stand out for their potential to modulate the output from Hippo and Hippo-like kinases, through their roles both in activating NDR kinases and in antagonizing upstream Hippo or Hippo-like kinase activity. These opposing Mob functions suggest that they coordinate the relative activities of the Tricornered/STK38/STK38L and Warts/LATS kinases, and thus have potential to assemble nodes for pathway signaling output. We survey the different facets of Mob-dependent regulation of Hippo and Hippo-like signaling and highlight open questions that hinge on unresolved aspects of Mob functions.

Recent Advances of the Hippo/YAP Signaling Pathway in Brain Development and Glioma

The Hippo signaling pathway is highly conserved from Drosophila melanogaster to mammals and plays a crucial role in organ size control, tissue regeneration, and tumor suppression. The Yes-associated protein (YAP) is an important transcriptional co-activator that is negatively regulated by the Hippo signaling pathway. The Hippo signaling pathway is also regulated by various upstream regulators, such as cell polarity, adhesion proteins, and other signaling pathways (the Wnt/β-catenin, Notch, and MAPK pathways). Recently, accumulated evidence suggests that the Hippo/YAP signaling pathway plays important roles in central nervous system development and brain tumor, including glioma. In this review, we summarize the results of recent studies on the physiological effect of the Hippo/YAP signaling pathway in neural stem cells, neural progenitor cells, and glial cells. In particular, we also focus on the expression of MST1/2, LATS1/2, and the downstream effector YAP, in glioma, and offer a review of the latest research of the Hippo/YAP signaling pathway in glioma pathogenesis. Finally, we also present future research directions and potential therapeutic strategies for targeting the Hippo/YAP signaling in glioma.

MOB (Mps one Binder) Proteins in the Hippo Pathway and Cancer

The family of MOBs (monopolar spindle-one-binder proteins) is highly conserved in the eukaryotic kingdom. MOBs represent globular scaffold proteins without any known enzymatic activities. They can act as signal transducers in essential intracellular pathways. MOBs have diverse cancer-associated cellular functions through regulatory interactions with members of the NDR/LATS kinase family. By forming additional complexes with serine/threonine protein kinases of the germinal centre kinase families, other enzymes and scaffolding factors, MOBs appear to be linked to an even broader disease spectrum. Here, we review our current understanding of this emerging protein family, with emphases on post-translational modifications, protein-protein interactions, and cellular processes that are possibly linked to cancer and other diseases. In particular, we summarise the roles of MOBs as core components of the Hippo tissue growth and regeneration pathway.

Roles of the MST1-JNK signaling pathway in apoptosis of colorectal cancer cells induced by Taurine

The aim of this study was to observe the impact of the mammalian sterile 20-like kinase 1-c-Jun N-terminal kinase (MST1-JNK) signaling pathway on apoptosis in colorectal cancer (CRC) cells induced by Taurine (Tau). Caco-2 and SW620 cells transfected with p-enhanced green fluorescent protein (EGFP)-MST1 or short interfering RNA (siRNA)-MST1 were treated with Tau for 48 h. Apoptosis was detected by flow cytometry, and the levels of MST1 and JNK were detected by western blotting. Compared with the control group, 80 mM Tau could significantly induce apoptosis of CRC cells, and the apoptotic rate increased with increasing Tau concentration (P < 0.01). Meanwhile, the protein levels of MST1 and phosphorylated (p)-JNK in Caco-2 cells increased significantly (P < 0.01). The apoptotic rate of the p-EGFP-MST1 plasmid-transfected cancer cells was significantly higher than that of the control group (P < 0.05); however, the apoptotic rate of the p-EGFP-MST1+Tau group was increased further (P < 0.01). Silencing the MST1 gene could decrease the apoptotic rate of cancer cells, and Tau treatment could reverse this decrease. Blocking the JNK signaling pathway significantly reduced the Tau-induced apoptotic rate of CRC cells. Thus, the MST1-JNK pathway plays an important role in Tau-induced apoptosis of CRC cells.

The MST4-MOB4 complex disrupts the MST1-MOB1 complex in the Hippo-YAP pathway and plays a pro-oncogenic role in pancreatic cancer

The mammalian STE20-like protein kinase 1 (MST1)-MOB kinase activator 1 (MOB1) complex has been shown to suppress the oncogenic activity of Yes-associated protein (YAP) in the mammalian Hippo pathway, which is involved in the development of multiple tumors, including pancreatic cancer (PC). However, it remains unclear whether other MST-MOB complexes are also involved in regulating Hippo-YAP signaling and have potential roles in PC. Here, we report that mammalian STE20-like kinase 4 (MST4), a distantly related ortholog of the MST1 kinase, forms a complex with MOB4 in a phosphorylation-dependent manner. We found that the overall structure of the MST4-MOB4 complex resembles that of the MST1-MOB1 complex, even though the two complexes exhibited opposite biological functions in PC. In contrast to the tumor-suppressor effect of the MST1-MOB1 complex, the MST4-MOB4 complex promoted growth and migration of PANC-1 cells. Moreover, expression levels of MST4 and MOB4 were elevated in PC and were positively correlated with each other, whereas MST1 expression was down-regulated. Because of divergent evolution of key interface residues, MST4 and MOB4 could disrupt assembly of the MST1-MOB1 complex through alternative pairing and thereby increased YAP activity. Collectively, these findings identify the MST4-MOB4 complex as a noncanonical regulator of the Hippo-YAP pathway with an oncogenic role in PC. Our findings highlight that although MST-MOB complexes display some structural conservation, they functionally diverged during their evolution.

The Possible Crosstalk of MOB2 With NDR1/2 Kinases in Cell Cycle and DNA Damage Signaling

This article is the authors' opinion of the roles of the signal transducer Mps one binder 2 (MOB2) in the control of cell cycle progression and the DNA Damage Response (DDR). We recently found that endogenous MOB2 is required to prevent the accumulation of endogenous DNA damage in order to prevent the undesired, and possibly detrimental, activation of cell cycle checkpoints. In this regard, it is noteworthy that MOB2 has been linked biochemically to the regulation of the NDR1/2 (aka STK38/STK38L) protein kinases, which themselves have functions at different steps of the cell cycle. Therefore, we are speculating in this article about the possible connections of MOB2 with NDR1/2 kinases in cell cycle and DDR Signaling.

Significance of expression of MST1 in homocysteine-induced hepatocyte apoptosis

AIM: To study the role of the mammalian sterile 20-like kinase 1 (MST1) gene in homocysteine-induced hepatocyte apoptosis.

METHODS: Five-week-old C57BL/6J mice of SPF grade were divided into four groups: a normal control group, an ApoE^-/- group, a high methionine diet group, and an intervention group (n = 12 each). In the normal control group, normal mice were fed a normal diet. In the ApoE^-/- group, male ApoE^-/- mice were fed a normal diet. In the high methionine diet group, male ApoE^-/- mice were fed a high methionine diet. In the intervention group, male ApoE^-/- mice were fed a high methionine diet plus folic acid and vitamin B₁₂. Transmission electron microscopy and DAPI staining were used to determine the level of apoptosis in hepatic tissue. qRT-PCR and Western blot were used to determine the expression of MST1. Hepatocytes were then cultured in the presence or absence of homocysteine (100 μmol/L) alone or 100 μmol/L homocysteine plus folic acid and vitamin B₁₂; flow cytometry was used to determine the level of hepatocytes apoptosis, and the expression of MST1 was detected by qRT-PCR and Western blot.

RESULTS: After the mice were fed for 14 wk, serum homocysteine level in the high methionine diet group was 2.3 and 1.9 times as high as that in the normal control group and the ApoE^-/- group (P < 0.01), respectively. Serum homocysteine level in the intervention group was 28% lower than that in the high methionine diet group (P < 0.01). These findings suggest that the model was successfully established. Electron microscopy showed that in the high methionine diet group, there were chromosome swelling or condensation, mitochondrial swelling, marked endoplasmic reticulum swelling and break, which suggested the trend of cell apoptosis in hepatic tissue. Compared with the normal control group and ApoE^-/- group, hepatic apoptosis level in the high methionine diet group was higher. However, hepatic apoptosis level in the intervention group was lower than that in the high methionine diet group. Compared with the normal control group and ApoE^-/- group, the expression of MST1 mRNA and protein in heapatic tissue in the high methionine diet group was upregulated (P < 0.05 or P < 0.01); however, MST1 expression in the intervention group was significantly lower than that in the high methionine diet group (P < 0.05). In vitro, compared with the normal control group, hepatocytes apoptosis level in the homocysteine alone group was significantly higher (P < 0.01); however, hepatocytes apoptosis level in the intervention group was significantly lower than that in the homocysteine alone group (P < 0.05). Compared with the normal control group, the expression of MST1 mRNA and protein in the homocysteine alone group was upregulated (P < 0.01); however, MST1 expression in the intervention group was significantly lower than that in the homocysteine alone group (P < 0.05).

CONCLUSION: MST1 expression is upregulated in homocysteine-induced hepatocyte apoptosis, and folic acid and vitamin B₁₂ can suppress the up-regulation of MST1.

Regulation of DNA damage responses and cell cycle progression by hMOB2

Mps one binder proteins (MOBs) are conserved regulators of essential signalling pathways. Biochemically, human MOB2 (hMOB2) can inhibit NDR kinases by competing with hMOB1 for binding to NDRs. However, biological roles of hMOB2 have remained enigmatic. Here, we describe novel functions of hMOB2 in the DNA damage response (DDR) and cell cycle regulation. hMOB2 promotes DDR signalling, cell survival and cell cycle arrest after exogenously induced DNA damage. Under normal growth conditions in the absence of exogenously induced DNA damage hMOB2 plays a role in preventing the accumulation of endogenous DNA damage and a subsequent p53/p21-dependent G1/S cell cycle arrest. Unexpectedly, these molecular and cellular phenotypes are not observed upon NDR manipulations, indicating that hMOB2 performs these functions independent of NDR signalling. Thus, to gain mechanistic insight, we screened for novel binding partners of hMOB2, revealing that hMOB2 interacts with RAD50, facilitating the recruitment of the MRE11-RAD50-NBS1 (MRN) DNA damage sensor complex and activated ATM to DNA damaged chromatin. Taken together, we conclude that hMOB2 supports the DDR and cell cycle progression.