TRIB2 regulates normal and stress-induced thymocyte proliferation

Tribbles Genes in Gastric Cancer: A Tumor-Suppressive Role for TRIB2

Tribbles pseudokinases (TRIB1-3) are important signaling modulators involved in several cancers. However, their function in gastric cancer (GC) remains undefined. GC is still a deadly disease since the lack of sensitive and specific biomarkers for early diagnosis and therapy response prediction negatively affects patients' outcome. The identification of novel molecular players may lead to more effective diagnostic and therapeutic avenues. Therefore, we investigated the role of TRIB genes in gastric tumorigenesis. Data mining of the TCGA dataset revealed that chromosomal instability (CIN) tumors have lower TRIB2 and higher TRIB3 expression versus microsatellite instability (MSI)-high tumors, while TRIB1 levels are similar in both tumor types. Moreover, in CIN tumors, low TRIB2 expression is significantly associated with aggressive stage IV disease. As no studies on TRIB2 in GC are available, we focused on this gene for further in vitro analyses. We checked the effect of TRIB2 overexpression (OE) on MKN45 and NCI-N87 CIN GC cell lines. In MKN45 cells, TRIB2 OE reduced proliferation and colony formation ability and induced G2/M arrest, while it decreased the proliferation and cell motility of NCI-N87 cells. These effects were not mediated by the MAPK pathway. Our results suggest a tumor-suppressive function of TRIB2 in GC with a CIN phenotype.

TRIB2 safeguards naive T cell homeostasis during aging

Naive CD4+ T cells are more resistant to age-related loss than naive CD8+ T cells, suggesting mechanisms that preferentially protect naive CD4+ T cells during aging. Here, we show that TRIB2 is more abundant in naive CD4+ than CD8+ T cells and counteracts quiescence exit by suppressing AKT activation. TRIB2 deficiency increases AKT activity and accelerates proliferation and differentiation in response to interleukin-7 (IL-7) in humans and during lymphopenia in mice. TRIB2 transcription is controlled by the lineage-determining transcription factors ThPOK and RUNX3. Ablation of Zbtb7b (encoding ThPOK) and Cbfb (obligatory RUNT cofactor) attenuates the difference in lymphopenia-induced proliferation between naive CD4+ and CD8+ cells. In older adults, ThPOK and TRIB2 expression wanes in naive CD4+ T cells, causing loss of naivety. These findings assign TRIB2 a key role in regulating T cell homeostasis and provide a model to explain the lesser resilience of CD8+ T cells to undergo changes with age.

A miRNAs catalogue from third-stage larvae and extracellular vesicles of Anisakis pegreffii provides new clues for host-parasite interplay

Anisakids are widespread marine parasites of medical, veterinary and economic relevance. They infect marine natural hosts but humans can accidentally acquire the fish-borne zoonosis anisakiasis by ingesting infected raw fishes or mollusks. Among the several species described, Anisakis pegreffii is one of the main etiological agent of the disease, in particular in the Mediterranean area. Despite the growing evidence of miRNAs involvement in host-parasite interplay, and the emerging role of exosomal microvesicles in shuttling them between different cell types (and sometime across species), no information on miRNAs from any Anisakis species is presently available. In this study we isolated extracellular vesicles (EVs) released by Anisakis pegreffii infective third-stage larvae (L3) and analyzed by RNA-seq small RNAs from both L3 and EVs. We showed by nanoparticle tracking analysis that L3 release in culture medium particles of size compatible with the one of extracellular vesicles. A catalogue of 156 miRNAs from A. pegreffii was compiled by sequence comparison to evolutionary close species and miRNA prediction software. Using differential expression analysis, we identified a small number of highly abundant miRNAs in larvae and extracellular vesicles fractions whose potential biological relevance may deserve future investigation. Finally, A. pegreffii miRNAs were compared to those described in other parasitic helminths and predicted targets among human genes were searched, suggesting their potential involvement during infection.

Expression and Related Mechanisms of miR-100 and TRIB2 in COPD Patients

Background

Chronic obstructive pulmonary disease (COPD) is one of the most common chronic respiratory diseases in the world. COPD is a general term for a class of lung diseases, including emphysema, chronic bronchitis, and refractory asthma. It is characterized by irreversible airflow obstruction and chronic tracheal inflammation.

Objective

This study aimed to investigate the expression and related mechanisms of miR-100 and TRIB2 in patients with COPD.

Methods

We collected the serum of patients admitted to our hospital and healthy volunteers undergoing physical examination at the same time, pulmonary fibroblasts were purchased for the experiments, miR-100 was overexpressed, and TRIB2 expression was inhibited in cells. The miR-100 and TRIB2 expression levels in serum and cells were detected by qRT-PCR and Western blot, cell proliferation and apoptosis were detected by CCK-8 and flow cytometry, and the relationship between miR-100 and TRIB2 was explored by the dual-luciferase report.

Results

The miR-100 expression in the serum of the COPD group was expressed normally, while the TRIB2 expression was expressed abnormally (p < 0.05). The AUC of serum miR-146a and TRIB2 for COPD diagnosis were 0.965 and 0.954, respectively. Overexpressing miR-100 and inhibiting the TRIB2 expression could decrease cell proliferation and increase apoptosis rate. According to the dual-luciferase report, miR-100 and TRIB2 had a targeted regulatory relationship. Rescue experiments showed that overexpressing TRIB2 could reverse the changes of cell proliferation and apoptosis caused by overexpression of miR-100.

Conclusion

miR-100 and TRIB2 were expressed abnormally in serum of COPD patients, and miR-100 could inhibit proliferation of pulmonary fibroblasts and promote their apoptosis.

The Pseudokinase TRIB1 in Immune Cells and Associated Disorders

Simple Summary

TRIB1 is at the center of major cell signaling pathways. In this review, we describe its role in immune cells and highlight TRIB1 interacting partners which suggests cell-specific functions and that TRIB1 is involved in cellular homeostasis and also in different cancers and immune-related disorders.

Abstract

Research advances in Tribbles homolog (TRIB) genes have established the consensus that this protein family plays roles in diverse biological conditions and regulates intracellular signaling networks and several human diseases. In this review, we focus on one member of the family, TRIB1, and its role at the crossroads of immune signaling. TRIB1 directly interacts with transcription factors such as FOXP3 and C/EBPα, with several signaling molecules such as MEK1 and MALT1 and directly acts on key cell signaling pathways such as the MAPK and NF-κB pathways. Altogether, these interactions emphasize that TRIB1 is at the center of major cell signaling pathways while TRIB1 has cell-specific roles, potentially depending on the expressing cells and binding partners. In this review, we describe its roles in immune cells and highlight the interacting partners explaining these functions which suggests TRIB1 as a precise mediator of cellular homeostasis as well as in different cancers and immune-related disorders.

Structure vs. Function of TRIB1-Myeloid Neoplasms and Beyond

The Tribbles family of proteins-comprising TRIB1, TRIB2, TRIB3 and more distantly related STK40-play important, but distinct, roles in differentiation, development and oncogenesis. Of the four Tribbles proteins, TRIB1 has been most well characterised structurally and plays roles in diverse cancer types. The most well-understood role of TRIB1 is in acute myeloid leukaemia, where it can regulate C/EBP transcription factors and kinase pathways. Structure-function studies have uncovered conformational switching of TRIB1 from an inactive to an active state when it binds to C/EBPα. This conformational switching is centred on the active site of TRIB1, which appears to be accessible to small-molecule inhibitors in spite of its inability to bind ATP. Beyond myeloid neoplasms, TRIB1 plays diverse roles in signalling pathways with well-established roles in tumour progression. Thus, TRIB1 can affect both development and chemoresistance in leukaemia; glioma; and breast, lung and prostate cancers. The pervasive roles of TRIB1 and other Tribbles proteins across breast, prostate, lung and other cancer types, combined with small-molecule susceptibility shown by mechanistic studies, suggests an exciting potential for Tribbles as direct targets of small molecules or biomarkers to predict treatment response.

The Critical Role of TRIB2 in Cancer and Therapy Resistance

Simple Summary

The Tribbles proteins are members of CAMK Ser/Thr protein kinase family. They are evolutionary conserved pseudokinases found in most tissues of eukaryotic organisms. This ubiquitously expressed protein family is characterized by containing a catalytically deficient kinase domain which lacks amino acid residues required for the productive interaction with ATP and metal ions. Tribbles proteins exert their biological functions mainly through direct interaction with MAPKK and AKT proteins, therefore regulating important pathways involved in cell proliferation, apoptosis and differentiation. Due to the role of MAPKK and AKT signalling in the context of cancer development, Tribbles proteins have been recently considered as biomarkers of cancer progression. Furthermore, as the atypical pseudokinase domain retains a binding platform for substrates, Tribbles targeting provides an attractive opportunity for drug development.

Abstract

The Tribbles pseudokinases family consists of TRIB1, TRIB2, TRIB3 and STK40 and, although evolutionarily conserved, they have distinctive characteristics. Tribbles members are expressed in a context and cell compartment-dependent manner. For example, TRIB1 and TRIB2 have potent oncogenic activities in vertebrate cells. Since the identification of Tribbles proteins as modulators of multiple signalling pathways, recent studies have linked their expression with several pathologies, including cancer. Tribbles proteins act as protein adaptors involved in the ubiquitin-proteasome degradation system, as they bridge the gap between substrates and E3 ligases. Between TRIB family members, TRIB2 is the most ancestral member of the family. TRIB2 is involved in protein homeostasis regulation of C/EBPα, β-catenin and TCF4. On the other hand, TRIB2 interacts with MAPKK, AKT and NFkB proteins, involved in cell survival, proliferation and immune response. Here, we review the characteristic features of TRIB2 structure and signalling and its role in many cancer subtypes with an emphasis on TRIB2 function in therapy resistance in melanoma, leukemia and glioblastoma. The strong evidence between TRIB2 expression and chemoresistance provides an attractive opportunity for targeting TRIB2.

Tribbles homolog 2 promotes hepatic fibrosis and hepatocarcinogenesis through phosphatase 1A-Mediated stabilization of yes-associated protein

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) play critical roles in liver fibrosis and hepatocellular carcinoma (HCC). Tribbles homolog 2 (TRIB2) is an oncogene implicated in a variety of cancers, including liver cancer. However, the biological function and regulatory mechanism of TRIB2 in HSCs are poorly understood. In addition, little is known about its role in liver fibrosis progression to HCC. Here, we revealed the clinical significance of TRIB2 in liver fibrosis and HCC development.

METHODS

We investigated TRIB2 promoting liver fibrosis in vitro and in vivo. In mouse model of liver fibrosis and HCC, we measured hepatic fibrosis and HCC level through knockdown TRIB2 with shRNA. In addition, we performed western blotting, real-time quantitative PCR, immunofluorescence and co-immunoprecipitation assay to study TRIB2 function in LX-2 cells.

RESULTS

TRIB2 expression was strongly upregulated in human fibrotic liver tissues and HCC tissues. TRIB2 colocalized with α-smooth muscle actin (α-SMA) in fibrotic and HCC liver tissues. Knockdown of TRIB2 inhibited HSC activation and liver fibrosis in vitro and in vivo. TRIB2 promoted Yes-associated protein (YAP) stabilization, nuclear localization, and subsequent fibrotic gene expression independent of the MST-LATS phosphorylation cascade in HSCs. TRIB2 interacted with YAP to recruit phosphatase 1A (PP1A), promoting PP1A-mediated YAP dephosphorylation. TRIB2 knockdown potently attenuated the development of fibrosis-associated liver cancer.

CONCLUSIONS

TRIB2 is an attractive target for hepatic fibrosis and fibrosis-associated liver cancer treatment.

Tribbles homolog 2 (Trib2), a pseudo serine/threonine kinase in tumorigenesis and stem cell fate decisions

The family of Tribbles proteins play many critical nonenzymatic roles and regulate a wide range of key signaling pathways. Tribbles homolog 2 (Trib2) is a pseudo serine/threonine kinase that functions as a scaffold or adaptor in various physiological and pathological processes. Trib2 can interact with E3 ubiquitin ligases and control protein stability of downstream effectors. This protein is induced by mitogens and enhances the propagation of several cancer cells, including myeloid leukemia, liver, lung, skin, bone, brain, and pancreatic. Thus, Trib2 can be a predictive and valuable biomarker for the diagnosis and treatment of cancer. Recent studies have illustrated that Trib2 plays a major role in cell fate determination of stem cells. Stem cells have the capacity to self-renew and differentiate into specific cell types. Stem cells are important sources for cell-based regenerative medicine and drug screening. Trib2 has been found to increase the self-renewal ability of embryonic stem cells, the reprogramming efficiency of somatic cells, and chondrogenesis. In this review, we will focus on the recent advances of Trib2 function in tumorigenesis and stem cell fate decisions.

Trib1 regulates T cell differentiation during chronic infection by restraining the effector program

In chronic infections, the immune response fails to control virus, leading to persistent antigen stimulation and the progressive development of T cell exhaustion. T cell effector differentiation is poorly understood in the context of exhaustion, but targeting effector programs may provide new strategies for reinvigorating T cell function. We identified Tribbles pseudokinase 1 (Trib1) as a central regulator of antiviral T cell immunity, where loss of Trib1 led to a sustained enrichment of effector-like KLRG1⁺ T cells, enhanced function, and improved viral control. Single-cell profiling revealed that Trib1 restrains a population of KLRG1⁺ effector CD8 T cells that is transcriptionally distinct from exhausted cells. Mechanistically, we identified an interaction between Trib1 and the T cell receptor (TCR) signaling activator, MALT1, which disrupted MALT1 signaling complexes. These data identify Trib1 as a negative regulator of TCR signaling and downstream function, and reveal a link between Trib1 and effector versus exhausted T cell differentiation that can be targeted to improve antiviral immunity.

TRIB3 promotes MYC-associated lymphoma development through suppression of UBE3B-mediated MYC degradation

The transcription factor MYC is deregulated in almost all human cancers, especially in aggressive lymphomas, through chromosomal translocation, amplification, and transcription hyperactivation. Here, we report that high expression of tribbles homologue 3 (TRIB3) positively correlates with elevated MYC expression in lymphoma specimens; TRIB3 deletion attenuates the initiation and progression of MYC-driven lymphoma by reducing MYC expression. Mechanistically, TRIB3 interacts with MYC to suppress E3 ubiquitin ligase UBE3B-mediated MYC ubiquitination and degradation, which enhances MYC transcriptional activity, causing high proliferation and self-renewal of lymphoma cells. Use of a peptide to disturb the TRIB3-MYC interaction together with doxorubicin reduces the tumor burden in Myc^Eμ mice and patient-derived xenografts. The pathophysiological relevance of UBE3B, TRIB3 and MYC is further demonstrated in human lymphoma. Our study highlights a key mechanism for controlling MYC expression and a potential therapeutic option for treating lymphomas with high TRIB3-MYC expression.

c-MYC is often deregulated in human cancers including lymphomas. Here, the authors show that a member of the pseudokinase family, tribbles homologue 3 (TRIB3), interacts with c-MYC to suppress c-MYC ubiquitination and degradation, leading to increased proliferation and self-renewal of lymphoma cells.

Functional effects of Tribbles homolog 2 in bovine ovarian granulosa cells†

Tribbles homologs (TRIB) 1, 2, and 3 represent atypical members of the serine/threonine kinase superfamily. We previously identified TRIB2 as a differentially expressed gene in granulosa cells (GCs) of bovine preovulatory follicles. The current study aimed to further investigate TRIB2 regulation and study its function in the ovary. GCs were collected from follicles at different developmental stages: small antral follicles (SF), dominant follicles (DF) at day 5 of the estrous cycle, and hCG-induced ovulatory follicles (OFs). RT-qPCR analyses showed greater expression of TRIB2 in GC of DF as compared to OF and a significant downregulation of TRIB2 steady-state mRNA amounts by hCG/LH, starting at 6 h through 24 h post-hCG as compared to 0 h. Specific anti-TRIB2 polyclonal antibodies were generated and western blot analysis confirmed TRIB2 downregulation by hCG at the protein level. In vitro studies showed that FSH stimulates TRIB2 expression in GC. Inhibition of TRIB2 using CRISPR/Cas9 resulted in a significant increase in PCNA expression and an increase in steroidogenic enzyme CYP19A1 expression, while TRIB2 overexpression tended to decrease GC proliferation. TRIB2 inhibition also resulted in a decrease in transcription factors connective tissue growth factor (CTGF) and ankyrin repeat domain-containing protein 1 (ANKRD1) expression, while TRIB2 overexpression increased CTGF and ANKRD1. Additionally, western blot analyses showed reduction in ERK1/2 (MAPK3/1) and p38MAPK (MAPK14) phosphorylation levels following TRIB2 inhibition, while TRIB2 overexpression increased p-ERK1/2 and p-p38MAPK. These results provide evidence that TRIB2 modulates MAPK signaling in GC and that TRIB2 could act as a regulator of GC proliferation and function, which could affect steroidogenesis during follicular development.

Pseudokinases: a tribble-edged sword

Advances in the understanding of the Tribbles family of pseudokinases (TRIB1, TRIB2 and TRIB3) reveal these proteins as potentially valuable biomarkers of disease diagnosis, prognosis, prediction and clinical strategy. In their role as signalling mediators and scaffolding proteins, TRIBs lead to changes in protein stability and activity, which impact on diverse cellular processes such as proliferation, differentiation, cell cycle and cell death. We review the role of TRIB proteins as promising therapeutic targets, with an emphasis on their role in cancer, and as biomarkers, with potential application across diverse pathological processes.

TRIB2 regulates the differentiation of MLL-TET1 transduced myeloid progenitor cells

The function and mechanism of action of MLL-TET1 (MT1) fusion protein in hematological cells are unclear and require further investigation. In the present study, we found that the MT1 fusion protein attenuated the expression of Cebpa, Csf1r, and Cd11b and inhibited the differentiation of myeloid progenitor cells. Increased binding of the MT1 fusion protein to the Trib2 promoter upregulated Trib2 mRNA and protein expression and downregulated Cebpa expression. Trib2 knockdown relieved the inhibition of myeloid cell differentiation induced by the MT1 fusion protein. Thus, TRIB2 is important for the survival of leukemia cells during MT1-related leukemogenesis and is important in maintaining differentiation blockade of leukemic cells. KEY MESSAGES: • MLL-TET1 fusion decreases the 5-hmC levels in the myeloid progenitor cells. • MLL-TET1 fusion inhibits myeloid differentiation through decreased expression of Cebpa. • MLL-TET1 fusion blocks the differentiation of the myeloid progenitor cells by overexpressing Trib2. • Knockdown of Trib2 in MLL-TET1 transduced cells induces myeloid differentiation.

Substrate binding allosterically relieves autoinhibition of the pseudokinase TRIB1

The Tribbles family of pseudokinases recruits substrates to the ubiquitin ligase COP1 to facilitate ubiquitylation. CCAAT/enhancer-binding protein (C/EBP) family transcription factors are crucial Tribbles substrates in adipocyte and myeloid cell development. We found that the TRIB1 pseudokinase was able to recruit various C/EBP family members and that the binding of C/EBPβ was attenuated by phosphorylation. To explain the mechanism of C/EBP recruitment, we solved the crystal structure of TRIB1 in complex with C/EBPα, which revealed that TRIB1 underwent a substantial conformational change relative to its substrate-free structure and bound C/EBPα in a pseudosubstrate-like manner. Crystallographic analysis and molecular dynamics and subsequent biochemical assays showed that C/EBP binding triggered allosteric changes that link substrate recruitment to COP1 binding. These findings offer a view of pseudokinase regulation with striking parallels to bona fide kinase regulation-by means of the activation loop and αC helix-and raise the possibility of small molecules targeting either the activation "loop-in" or "loop-out" conformations of Tribbles pseudokinases.

Oncogenic transcriptional program driven by TAL1 in T-cell acute lymphoblastic leukemia

TAL1/SCL is a prime example of an oncogenic transcription factor that is abnormally expressed in acute leukemia due to the replacement of regulator elements. This gene has also been recognized as an essential regulator of hematopoiesis. TAL1 expression is strictly regulated in a lineage- and stage-specific manner. Such precise control is crucial for the switching of the transcriptional program. The misexpression of TAL1 in immature thymocytes leads to a widespread series of orchestrated downstream events that affect several different cellular machineries, resulting in a lethal consequence, namely T-cell acute lymphoblastic leukemia (T-ALL). In this article, we will discuss the transcriptional regulatory network and downstream target genes, including protein-coding genes and non-coding RNAs, controlled by TAL1 in normal hematopoiesis and T-cell leukemogenesis.

Inverse and correlative relationships between TRIBBLES genes indicate non-redundant functions during normal and malignant hemopoiesis

TRIBBLES pseudokinases (TRIB1, TRIB2, and TRIB3) are important regulators of normal and malignant hemopoiesis. The relative abundance of each TRIBBLES family member may be important for distinct oncogenic or tumor suppressor functions. We map the expression profiles of TRIB1, TRIB2, and TRIB3 in human and murine hemopoietic stem, progenitor and mature cells, and in human leukemia datasets. Our data show that TRIB1-TRIB2 have an inverse expression relationship in normal hemopoiesis, whereas TRIB1-TRIB3 have a positive correlation. We reveal that TRIB3 expression is high in the dormant hemopoietic stem cell (HSC) population, implicating a novel role for TRIB3 in stem cell quiescence. These analyses support a non-redundant role for each TRIBBLES member during normal hemopoietic differentiation. We show that TRIB1-TRIB2 display a significant negative correlation in myelodysplastic syndrome and acute myeloid leukemia (AML) subtypes, but not in acute lymphoid leukemia. This inverse relationship is specific to certain subtypes of AML. A positive correlation exists in different leukemia subtypes between TRIB1-TRIB3. The TRIB1-TRIB2 and TRIB1-TRIB3 correlations are consistent with a correlative relationship with C/EBP transcription factor family members. Our results have implications for the development of strategies to therapeutically target these genes in different types of leukemia.

A Trib2-p38 axis controls myeloid leukaemia cell cycle and stress response signalling

Trib2 pseudokinase is involved in the etiology of a number of cancers including leukaemia, melanoma, ovarian, lung and liver cancer. Both high and low Trib2 expression levels correlate with different types of cancer. Elevated Trib2 expression has oncogenic properties in both leukaemia and lung cancer dependent on interactions with proteasome machinery proteins and degradation of transcription factors. Here, we demonstrated that Trib2 deficiency conferred a growth and survival advantage both at steady state and in stress conditions in leukaemia cells. In response to stress, wild type leukaemia cells exited the cell cycle and underwent apoptosis. In contrast, Trib2 deficient leukaemia cells continued to enter mitosis and survive. We showed that Trib2 deficient leukaemia cells had defective MAPK p38 signalling, which associated with a reduced γ-H2Ax and Chk1 stress signalling response, and continued proliferation following stress, associated with inefficient activation of cell cycle inhibitors p21, p16 and p19. Furthermore, Trib2 deficient leukaemia cells were more resistant to chemotherapy than wild type leukaemia cells, having less apoptosis and continued propagation. Trib2 re-expression or pharmacological activation of p38 in Trib2 deficient leukaemia cells sensitised the cells to chemotherapy-induced apoptosis comparable with wild type leukaemia cells. Our data provide evidence for a tumour suppressor role of Trib2 in myeloid leukaemia via activation of p38 stress signalling. This newly identified role indicates that Trib2 may counteract the propagation and chemotherapy resistance of leukaemia cells.

Trib2 expression in granulocyte-monocyte progenitors drives a highly drug resistant acute myeloid leukaemia linked to elevated Bcl2

Trib2 pseudokinase has oncogenic and tumour suppressive functions depending on the cellular context. We investigated the ability of Trib2 to transform different haemopoietic stem and progenitor cells (HSPCs). Our study identified the granulocyte-macrophage progenitor (GMP) subpopulation as a potent leukaemia initiating cell of Trib2-driven AML in vivo. Trib2 transformed GMPs generated a fully penetrant and short latency AML. AML cells expressing elevated Trib2 led to a chemoresistant phenotype following chemotherapy treatment. We show that Trib2 overexpression results in an increase in BCL2 expression, and high Trib2 expressing cells are highly sensitive to cell killing by BCL2 inhibition (ABT199). Combined treatment with chemotherapeutic agents and BCL2 inhibition resulted in synergistic killing of Trib2+ AML cells. Trib2 transformed GMP AML cells showed more chemoresistance compared with HSPC derived Trib2 AML cells associated with higher Bcl2 expression. There is significant correlation of high TRIB2 and BCL2 expression in patient derived human AML cells. These data demonstrate that the cell of origin influences the leukaemic profile and chemotherapeutic response of Trib2+ AML. Combined TRIB2 and BCL2 expression in AML cells may have clinical utility relevant for monitoring drug resistance and disease relapse.

Identifying Genetic Differences Between Dongxiang Blue-Shelled and White Leghorn Chickens Using Sequencing Data

The Dongxiang Blue-shelled chicken is one of the most valuable Chinese indigenous poultry breeds. However, compared to the Italian native White Leghorn, although this Chinese breed possesses numerous favorable characteristics, it also exhibits lower growth performance and fertility. Here, we utilized genotyping sequencing data obtained via genome reduction on a sequencing platform to detect 100,114 single nucleotide polymorphisms and perform further biological analysis and functional annotation. We employed cross-population extended haplotype homozygosity, eigenvector decomposition combined with genome-wide association studies (EigenGWAS), and efficient mixed-model association expedited methods to detect areas of the genome that are potential selected regions (PSR) in both chicken breeds, and performed gene ontology (GO) enrichment and quantitative trait loci (QTL) analyses annotating using the Kyoto Encyclopedia of Genes and Genomes. The results of this study revealed a total of 2424 outlier loci (p-value <0.01), of which 2144 occur in the White Leghorn breed and 280 occur in the Dongxiang Blue-shelled chicken. These correspond to 327 and 94 PSRs containing 297 and 54 genes, respectively. The most significantly selected genes in Blue-shelled chicken are TMEM141 and CLIC3, while the SLCO1B3 gene, related to eggshell color, was identified via EigenGWAS. We show that the White Leghorn genes JARID2, RBMS3, GPC3, TRIB2, ROBO1, SAMSN1, OSBP2, and IGFALS are involved in immunity, reproduction, and growth, and thus might represent footprints of the selection process. In contrast, we identified six significantly enriched pathways in the Dongxiang Blue-shelled chicken that are related to amino acid and lipid metabolism as well as signal transduction. Our results also reveal the presence of a GO term associated with cell metabolism that occurs mainly in the White Leghorn breed, while the most significant QTL regions mapped to the Chicken QTL Database (GG_4.0) for the Dongxiang Blue-shelled breed are predominantly related to lesions, bone mineral content, and other related traits compared to tibia length and body weight (i.e., at 14, 28, 42, and 70 d) in the White Leghorn. The results of this study highlight differences in growth, immunity, and egg quality traits between the two breeds, and provide a foundation for the exploration of their genetic mechanisms.

TRIB3 Promotes APL Progression through Stabilization of the Oncoprotein PML-RARα and Inhibition of p53-Mediated Senescence

Acute promyelocytic leukemia (APL) is driven by the oncoprotein PML-RARα, which antagonizes myeloid differentiation and promotes APL-initiating cell self-renewal. Combined all-trans retinoic acid (ATRA) with arsenic trioxide (As₂O₃) or chemotherapy dramatically improves the prognosis of APL patients. Here we report that expression of pseudokinase Tribble 3 (TRIB3) associates positively with APL progression and therapeutic resistance. The elevated TRIB3 expression promotes APL by interacting with PML-RARα and suppressing its sumoylation, ubiquitylation, and degradation. This represses PML nuclear body assembly, p53-mediated senescence, and cell differentiation, and supports cellular self-renewal. Genetically inhibiting TRIB3 expression or combination of a peptide disturbing TRIB3/PML-RARα interaction with ATRA/As₂O₃ eradicates APL by accelerating PML-RARα degradation. Our study provides insight into APL pathogenesis and a potential therapeutic option against APL.

Tribbles in the 21st Century: The Evolving Roles of Tribbles Pseudokinases in Biology and Disease

The Tribbles (TRIB) pseudokinases control multiple aspects of eukaryotic cell biology and evolved unique features distinguishing them from all other protein kinases. The atypical pseudokinase domain retains a regulated binding platform for substrates, which are ubiquitinated by context-specific E3 ligases. This plastic configuration has also been exploited as a scaffold to support the modulation of canonical MAPK and AKT modules. In this review, we discuss the evolution of TRIBs and their roles in vertebrate cell biology. TRIB2 is the most ancestral member of the family, whereas the emergence of TRIB3 homologs in mammals supports additional biological roles, many of which are currently being dissected. Given their pleiotropic role in diseases, the unusual TRIB pseudokinase conformation provides a highly attractive opportunity for drug design.

Pseudoenzymes are inactive counterparts of classical enzymes and have evolved in all kingdoms of life, where they regulate a vast array of biological processes. The pseudokinases are one of the best-studied families of human pseudoenzymes.

Eukaryotic TRIB pseudokinases evolved from a common ancestor (the human TRIB2 homolog), and contain a highly atypical pseudokinase domain fused to a unique docking site in an extended C tail that binds to ubiquitin E3 ligases.

TRIB evolution has led to the appearance of three mammalian TRIB pseudokinases, termed TRIB1, TRIB2, and TRIB3, which contain both unique and shared features.

In cells, TRIB pseudokinases act as modulators of substrate ubiquitination and as molecular scaffolds for the assembly and regulation of signaling modules, including the C/EBPα transcription factor and AKT and ERK networks.

TRIB1 and TRIB2 have potent oncogenic activities in vertebrate cells, and recent evidence also suggests that TRIB2 acts as a tumour suppressor, consistent with the requirement for balanced TRIB signaling in the regulation of transcription, differentiation, proliferation, and apoptosis.

Human TRIB2 Oscillates during the Cell Cycle and Promotes Ubiquitination and Degradation of CDC25C

Tribbles homolog 2 (TRIB2) is a member of the mammalian Tribbles family of serine/threonine pseudokinases (TRIB1-3). Studies of TRIB2 indicate that many of the molecular interactions between the single Drosophila Tribbles (Trbl) protein and interacting partners are evolutionary conserved. In this study, we examined the relationship between TRIB2 and cell division cycle 25 (CDC25) family of dual-specificity protein phosphatases (mammalian homologues of Drosophila String), which are key physiological cell cycle regulators. Using co-immunoprecipitation we demonstrate that TRIB2 interacts with CDC25B and CDC25C selectively. Forced overexpression of TRIB2 caused a marked decrease in total CDC25C protein levels. Following inhibition of the proteasome, CDC25C was stabilized in the nuclear compartment. This implicates TRIB2 as a regulator of nuclear CDC25C turnover. In complementary ubiquitination assays, we show that TRIB2-mediated degradation of CDC25C is associated with lysine-48-linked CDC25C polyubiquitination driven by the TRIB2 kinase-like domain. A cell cycle associated role for TRIB2 is further supported by the cell cycle regulated expression of TRIB2 protein levels. Our findings reveal mitotic CDC25C as a new target of TRIB2 that is degraded via the ubiquitin proteasome system. Inappropriate CDC25C regulation could mechanistically underlie TRIB2 mediated regulation of cellular proliferation in neoplastic cells.