RESUMEN
A proper balance between the repair of DNA double-strand breaks (DSBs) by homologous recombination and nonhomologous end joining is critical for maintaining genome integrity and preventing tumorigenesis. This balance is regulated and fine-tuned by a variety of factors, including cell cycle and the chromatin environment. The histone acetyltransferase TIP60 was previously shown to suppress pathological end joining and promote homologous recombination. However, it is unknown how regulatory posttranslational modifications impact TIP60 acetyltransferase activity to influence the outcome of DSB responses. In this study, we report that phosphorylation of TIP60 on serines 90 and 86 is important for limiting the accumulation of the pro-end joining factor 53BP1 at DSBs in S and G2 cell cycle phases. Mutation of these sites disrupts histone acetylation changes in response to DNA damage, BRCA1 localization to DSBs, and poly(ADP-ribose) polymerase (PARP) inhibitor resistance. These findings reveal that phosphorylation directs TIP60-dependent acetylation to promote homologous recombination and maintain genome stability.
Asunto(s)
Reparación del ADN/genética , Lisina Acetiltransferasa 5/genética , Transactivadores/genética , Proteína 1 de Unión al Supresor Tumoral P53/genética , Animales , Cromatina/metabolismo , Roturas del ADN de Doble Cadena , Reparación del ADN por Unión de Extremidades/genética , Inestabilidad Genómica/genética , Histonas/metabolismo , Recombinación Homóloga/genética , Ratones Transgénicos , Fosforilación , Procesamiento Proteico-Postraduccional/genéticaRESUMEN
Primary cilia are polarized organelles that allow detection of extracellular signals such as Hedgehog (Hh). How the cytoskeleton supporting the cilium generates and maintains a structure that finely tunes cellular response remains unclear. Here, we find that regulation of actin polymerization controls primary cilia and Hh signaling. Disrupting actin polymerization, or knockdown of N-WASp/Arp3, increases ciliation frequency, axoneme length, and Hh signaling. Cdc42, a potent actin regulator, recruits both atypical protein pinase C iota/lambda (aPKC) and Missing-in-Metastasis (MIM) to the basal body to maintain actin polymerization and restrict axoneme length. Transcriptome analysis implicates the Src pathway as a major aPKC effector. aPKC promotes whereas MIM antagonizes Src activity to maintain proper levels of primary cilia, actin polymerization, and Hh signaling. Hh pathway activation requires Smoothened-, Gli-, and Gli1-specific activation by aPKC. Surprisingly, longer axonemes can amplify Hh signaling, except when aPKC is disrupted, reinforcing the importance of the Cdc42-aPKC-Gli axis in actin-dependent regulation of primary cilia signaling.
Asunto(s)
Actinas/metabolismo , Cilios/metabolismo , Proteínas Hedgehog/metabolismo , Proteína de Unión al GTP cdc42/metabolismo , Células 3T3 , Proteína 3 Relacionada con la Actina/genética , Animales , Axonema/fisiología , Cuerpos Basales/metabolismo , Línea Celular , Activación Enzimática/fisiología , Regulación de la Expresión Génica/fisiología , Ratones , Proteínas de Microfilamentos/metabolismo , Proteínas de Neoplasias/metabolismo , Polimerizacion , Proteína Quinasa C/metabolismo , Transducción de Señal/fisiología , Proteína Neuronal del Síndrome de Wiskott-Aldrich/genética , Proteína con Dedos de Zinc GLI1/metabolismo , Familia-src Quinasas/metabolismoRESUMEN
DNA double-strand breaks are repaired by nonhomologous end-joining (NHEJ) and homologous recombination (HR). Disrupting the balance between these pathways results in toxic chromosomal rearrangements. Several recent studies are revealing that dynamic changes in chromatin conformation can regulate DNA repair pathway choice both spatially and temporally.
Asunto(s)
Proteína BRCA1/fisiología , Histonas/fisiología , HumanosRESUMEN
Growth of basal cell carcinomas (BCCs) requires high levels of hedgehog (HH) signalling through the transcription factor GLI. Although inhibitors of membrane protein smoothened (SMO) effectively suppress HH signalling, early tumour resistance illustrates the need for additional downstream targets for therapy. Here we identify atypical protein kinase C ι/λ (aPKC-ι/λ) as a novel GLI regulator in mammals. aPKC-ι/λ and its polarity signalling partners co-localize at the centrosome and form a complex with missing-in-metastasis (MIM), a scaffolding protein that potentiates HH signalling. Genetic or pharmacological loss of aPKC-ι/λ function blocks HH signalling and proliferation of BCC cells. Prkci is a HH target gene that forms a positive feedback loop with GLI and exists at increased levels in BCCs. Genome-wide transcriptional profiling shows that aPKC-ι/λ and SMO control the expression of similar genes in tumour cells. aPKC-ι/λ functions downstream of SMO to phosphorylate and activate GLI1, resulting in maximal DNA binding and transcriptional activation. Activated aPKC-ι/λ is upregulated in SMO-inhibitor-resistant tumours and targeting aPKC-ι/λ suppresses signalling and growth of resistant BCC cell lines. These results demonstrate that aPKC-ι/λ is critical for HH-dependent processes and implicates aPKC-ι/λ as a new, tumour-selective therapeutic target for the treatment of SMO-inhibitor-resistant cancers.
Asunto(s)
Carcinoma Basocelular/metabolismo , Carcinoma Basocelular/patología , Isoenzimas/metabolismo , Factores de Transcripción de Tipo Kruppel/metabolismo , Proteína Quinasa C/metabolismo , Factores de Transcripción/metabolismo , Animales , Carcinoma Basocelular/tratamiento farmacológico , Carcinoma Basocelular/enzimología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Centrosoma/metabolismo , Resistencia a Antineoplásicos , Retroalimentación Fisiológica , Proteínas Hedgehog/metabolismo , Humanos , Isoenzimas/antagonistas & inhibidores , Isoenzimas/genética , Queratinocitos/metabolismo , Factores de Transcripción de Tipo Kruppel/genética , Ratones , Fosforilación , Proteína Quinasa C/antagonistas & inhibidores , Proteína Quinasa C/genética , Receptores Acoplados a Proteínas G/antagonistas & inhibidores , Receptores Acoplados a Proteínas G/metabolismo , Transducción de Señal/efectos de los fármacos , Receptor Smoothened , Proteína con Dedos de Zinc GLI1RESUMEN
BRCA1 and BRCA2 are two major breast and ovarian cancer susceptibility genes. BRCA1 was the first discovered and has been a focus of research for these cancers. BRCA1 mediates tumor suppression in part through pleiotropic interactions with a network of DNA repair proteins on chromatin. BRCA1 mutations cause homologous recombination (HR)-mediated DNA repair deficiency, genomic instability, and DNA-damaging agent hypersensitivity. Although BRCA1 and BRCA2 have some shared functions in cancer predisposition and therapy response, there are also key differences indicating divergent roles for each protein. This review summarizes and highlights recent insights into the molecular events responsible for BRCA1 tumor suppression, emphasizing the DNA repair function of BRCA1 as a nexus between its roles in cancer development and therapy.
Asunto(s)
Proteína BRCA1/genética , Genoma , Neoplasias/genética , Animales , Proteína BRCA1/química , Proteína BRCA1/metabolismo , Daño del ADN , Reparación del ADN , ADN de Neoplasias/genética , HumanosRESUMEN
The primary cilium is critical for transducing Sonic hedgehog (Shh) signaling, but the mechanisms of its transient assembly are poorly understood. Previously we showed that the actin regulatory protein Missing-in-Metastasis (MIM) regulates Shh signaling, but the nature of MIM's role was unknown. Here we show that MIM is required at the basal body of mesenchymal cells for cilia maintenance, Shh responsiveness, and de novo hair follicle formation. MIM knockdown results in increased Src kinase activity and subsequent hyperphosphorylation of the actin regulator Cortactin. Importantly, inhibition of Src or depletion of Cortactin compensates for the cilia defect in MIM knockdown cells, whereas overexpression of Src or phospho-mimetic Cortactin is sufficient to inhibit ciliogenesis. Our results suggest that MIM promotes ciliogenesis by antagonizing Src-dependent phosphorylation of Cortactin and describe a mechanism linking regulation of the actin cytoskeleton with ciliogenesis and Shh signaling during tissue regeneration.