RESUMEN
Specific functions of the immune system are essential to protect us from infections caused by pathogens such as viruses and bacteria. However, as we age, the immune system shows a functional decline that can be attributed in large part to age-associated defects in hematopoietic stem cells (HSCs)-the cells at the apex of the immune cell hierarchy. Here, we find that the Hippo pathway coactivator TAZ is potently induced in old HSCs and protects these cells from functional decline. We identify Clca3a1 as a TAZ-induced gene that allows us to trace TAZ activity in vivo. Using CLCA3A1 as a marker, we can isolate "young-like" HSCs from old mice. Mechanistically, Taz acts as coactivator of PU.1 and to some extent counteracts the gradual loss of PU.1 expression during HSC aging. Our work thus uncovers an essential role for Taz in a previously undescribed fail-safe mechanism in aging HSCs.
Asunto(s)
Envejecimiento , Células Madre Hematopoyéticas , Envejecimiento/fisiología , Animales , Células Madre Hematopoyéticas/metabolismo , RatonesRESUMEN
Controlling cell proliferation is critical for organism development, tissue homeostasis, disease, and regeneration. IQGAP3 has been shown to be required for proper cell proliferation and migration, and is associated to a number of cancers. Moreover, its expression is inversely correlated with the overall survival rate in the majority of cancers. Here, we show that IQGAP3 expression is elevated in cervical cancer and that in these cancers IQGAP3 high expression is correlated with an increased lethality. Furthermore, we demonstrate that IQGAP3 is a target of YAP, a regulator of cell cycle gene expression. IQGAP3 knockdown resulted in an increased percentage of HeLa cells in S phase, delayed progression through mitosis, and caused multipolar spindle formation and consequentially aneuploidy. Protein-protein interaction studies revealed that IQGAP3 interacts with MMS19, which is known in Drosophila to permit, by competitive binding to Xpd, Cdk7 to be fully active as a Cdk-activating kinase (CAK). Notably, IQGAP3 knockdown caused decreased MMS19 protein levels and XPD knockdown partially rescued the reduced proliferation rate upon IQGAP3 knockdown. This suggests that IQGAP3 modulates the cell cycle via the MMS19/XPD/CAK axis. Thus, in addition to governing proliferation and migration, IQGAP3 is a critical regulator of mitotic progression and genome stability. IMPLICATIONS: Our data indicate that, while IQGAP3 inhibition might be initially effective in decreasing cancer cell proliferation, this approach harbors the risk to promote aneuploidy and, therefore, the formation of more aggressive cancers.
Asunto(s)
Proteínas de Ciclo Celular/genética , Ciclo Celular/genética , Proteínas Activadoras de GTPasa/genética , Inestabilidad Genómica/genética , Factores de Transcripción/genética , Animales , Línea Celular , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular/genética , Drosophila/genética , Células HCT116 , Células HEK293 , Células HeLa , Humanos , Mitosis/genética , Mapas de Interacción de Proteínas/genética , Transducción de Señal/genéticaRESUMEN
The Hippo signalling pathway and its central effector YAP regulate proliferation of cardiomyocytes and growth of the heart. Using genetic models in mice we show that the increased proliferation of embryonal and postnatal cardiomyocytes due to loss of the Hippo-signaling component SAV1 depends on the Myb-MuvB (MMB) complex. Similarly, proliferation of postnatal cardiomyocytes induced by constitutive active YAP requires MMB. Genome studies revealed that YAP and MMB regulate an overlapping set of cell cycle genes in cardiomyocytes. Protein-protein interaction studies in cell lines and with recombinant proteins showed that YAP binds directly to B-MYB, a subunit of MMB, in a manner dependent on the YAP WW domains and a PPXY motif in B-MYB. Disruption of the interaction by overexpression of the YAP binding domain of B-MYB strongly inhibits the proliferation of cardiomyocytes. Our results point to MMB as a critical downstream effector of YAP in the control of cardiomyocyte proliferation.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/química , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas de Ciclo Celular/genética , Miocitos Cardíacos/citología , Transactivadores/química , Transactivadores/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Animales Recién Nacidos , Sitios de Unión , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Proliferación Celular , Regulación de la Expresión Génica , Células HEK293 , Células HeLa , Humanos , Ratones , Complejos Multiproteicos/química , Complejos Multiproteicos/genética , Complejos Multiproteicos/metabolismo , Miocitos Cardíacos/química , Regiones Promotoras Genéticas , Ratas , Proteínas Señalizadoras YAPRESUMEN
YAP and TAZ, downstream effectors of the Hippo pathway, are important regulators of proliferation. Here, we show that the ability of YAP to activate mitotic gene expression is dependent on the Myb-MuvB (MMB) complex, a master regulator of genes expressed in the G2/M phase of the cell cycle. By carrying out genome-wide expression and binding analyses, we found that YAP promotes binding of the MMB subunit B-MYB to the promoters of mitotic target genes. YAP binds to B-MYB and stimulates B-MYB chromatin association through distal enhancer elements that interact with MMB-regulated promoters through chromatin looping. The cooperation between YAP and B-MYB is critical for YAP-mediated entry into mitosis. Furthermore, the expression of genes coactivated by YAP and B-MYB is associated with poor survival of cancer patients. Our findings provide a molecular mechanism by which YAP and MMB regulate mitotic gene expression and suggest a link between two cancer-relevant signaling pathways.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Adenocarcinoma del Pulmón/patología , Proteínas de Ciclo Celular/metabolismo , Ciclo Celular , Cromatina/metabolismo , Regulación de la Expresión Génica , Mitosis/genética , Transactivadores/metabolismo , Factores de Transcripción/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Adenocarcinoma del Pulmón/genética , Adenocarcinoma del Pulmón/metabolismo , Animales , Mama/citología , Mama/metabolismo , Proteínas de Ciclo Celular/genética , Células Cultivadas , Cromatina/genética , Elementos de Facilitación Genéticos , Femenino , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Ratones , Pronóstico , Regiones Promotoras Genéticas , Tasa de Supervivencia , Transactivadores/genética , Factores de Transcripción/genética , Proteínas Señalizadoras YAPRESUMEN
GAS2L3 is a recently identified cytoskeleton-associated protein that interacts with actin filaments and tubulin. The in vivo function of GAS2L3 in mammals remains unknown. Here, we show that mice deficient in GAS2L3 die shortly after birth because of heart failure. Mammalian cardiomyocytes lose the ability to proliferate shortly after birth, and further increase in cardiac mass is achieved by hypertrophy. The proliferation arrest of cardiomyocytes is accompanied by binucleation through incomplete cytokinesis. We observed that GAS2L3 deficiency leads to inhibition of cardiomyocyte proliferation and to cardiomyocyte hypertrophy during embryonic development. Cardiomyocyte-specific deletion of GAS2L3 confirmed that the phenotype results from the loss of GAS2L3 in cardiomyocytes. Cardiomyocytes from Gas2l3-deficient mice exhibit increased expression of a p53-transcriptional program including the cell cycle inhibitor p21. Furthermore, loss of GAS2L3 results in premature binucleation of cardiomyocytes accompanied by unresolved midbody structures. Together these results suggest that GAS2L3 plays a specific role in cardiomyocyte cytokinesis and proliferation during heart development.