RESUMO
In this issue of Molecular Cell, Yata et al. (2012) show that the mitotic kinase and cell-cycle regulator Plk1 can directly stimulate the DNA repair process, providing a potential mechanism of crosstalk between DNA repair and cell-cycle signaling.
Assuntos
Caseína Quinase II/metabolismo , Proteínas de Ciclo Celular/metabolismo , Quebras de DNA de Cadeia Dupla , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Rad51 Recombinase/metabolismo , Reparo de DNA por Recombinação , Humanos , Quinase 1 Polo-LikeRESUMO
Tyr142, the C-terminal amino acid of histone variant H2A.X is phosphorylated by WSTF (Williams-Beuren syndrome transcription factor), a component of the WICH complex (WSTF-ISWI chromatin-remodeling complex), under basal conditions in the cell. In response to DNA double-strand breaks (DSBs), H2A.X is instantaneously phosphorylated at Ser139 by the kinases ATM and ATR and is progressively dephosphorylated at Tyr142 by the Eya1 and Eya3 tyrosine phosphatases, resulting in a temporal switch from a postulated diphosphorylated (pSer139, pTyr142) to monophosphorylated (pSer139) H2A.X state. How mediator proteins interpret these two signals remains a question of fundamental interest. We provide structural, biochemical, and cellular evidence that Microcephalin (MCPH1), an early DNA damage response protein, can read both modifications via its tandem BRCA1 C-terminal (BRCT) domains, thereby emerging as a versatile sensor of H2A.X phosphorylation marks. We show that MCPH1 recruitment to sites of DNA damage is linked to both states of H2A.X.
Assuntos
Reparo do DNA/fisiologia , Histonas/metabolismo , Modelos Moleculares , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/metabolismo , Fosfosserina/metabolismo , Fosfotirosina/metabolismo , Calorimetria , Proteínas de Ciclo Celular , Clonagem Molecular , Cristalografia por Raios X , Proteínas do Citoesqueleto , Dano ao DNA/fisiologia , Escherichia coli , Vetores Genéticos/genética , Humanos , Microscopia de Fluorescência , Proteínas do Tecido Nervoso/genéticaRESUMO
The LIN-1 ETS transcription factor plays a pivotal role in controlling cell fate decisions during development of the Caenorhabditis elegans vulva. Prior to activation of the RTK/Ras/ERK-signaling pathway, LIN-1 functions as a SUMOylated transcriptional repressor that inhibits vulval cell fate. Here we demonstrate using the yeast two-hybrid system that SUMOylation of LIN-1 mediates interactions with a protein predicted to be involved in transcriptional repression: the RAD-26 Mi-2ß/CHD4 component of the nucleosome remodeling and histone deacetylation (NuRD) transcriptional repression complex. Genetic studies indicated that rad-26 functions to inhibit vulval cell fates in worms. Using the yeast two-hybrid system, we showed that the EGL-27/MTA1 component of the NuRD complex binds the carboxy-terminus of LIN-1 independently of LIN-1 SUMOylation. EGL-27 also binds UBC-9, an enzyme involved in SUMOylation, and MEP-1, a zinc-finger protein previously shown to bind LIN-1. Genetic studies indicate that egl-27 inhibits vulval cell fates in worms. These results suggest that LIN-1 recruits multiple proteins that repress transcription via both the SUMOylated amino-terminus and the unSUMOylated carboxy-terminus. Assays in cultured cells showed that the carboxy-terminus of LIN-1 was converted to a potent transcriptional activator in response to active ERK. We propose a model in which LIN-1 recruits multiple transcriptional repressors to inhibit the 1° vulval cell fate, and phosphorylation by ERK converts LIN-1 to a transcriptional activator that promotes the 1° vulval cell fate.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Regulação da Expressão Gênica , Proteínas Repressoras/metabolismo , Transativadores/metabolismo , Fatores de Transcrição/metabolismo , Animais , Proteínas de Caenorhabditis elegans/genética , Feminino , Complexo Mi-2 de Remodelação de Nucleossomo e Desacetilase/metabolismo , Fosforilação , Proteínas Repressoras/genética , Sumoilação , Transativadores/genética , Fatores de Transcrição/genética , Técnicas do Sistema de Duplo-Híbrido , Enzimas de Conjugação de Ubiquitina/metabolismo , Vulva/fisiologiaAssuntos
Proteínas de Ciclo Celular/metabolismo , Proteínas de Drosophila , Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Fuso Acromático/metabolismo , Proteínas de Xenopus/metabolismo , Animais , Ciclina B/metabolismo , Drosophila/genética , Drosophila/metabolismo , Humanos , Mitose , Modelos Moleculares , Fosforilação , Proteínas Serina-Treonina Quinases/genética , Estrutura Terciária de Proteína , Proteínas Proto-Oncogênicas , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Fosfatases cdc25/metabolismo , Quinase 1 Polo-LikeRESUMO
The DNA damage response depends on the concerted activity of protein serine/threonine kinases and modular phosphoserine/threonine-binding domains to relay the damage signal and recruit repair proteins. The PIKK family of protein kinases, which includes ATM/ATR/DNA-PK, preferentially phosphorylate Ser-Gln sites, while their basophilic downstream effecter kinases, Chk1/Chk2/MK2 preferentially phosphorylate hydrophobic-X-Arg-X-X-Ser/Thr-hydrophobic sites. A subset of tandem BRCT domains act as phosphopeptide binding modules that bind to ATM/ATR/DNA-PK substrates after DNA damage. Conversely, 14-3-3 proteins interact with substrates of Chk1/Chk2/MK2. FHA domains have been shown to interact with substrates of ATM/ATR/DNA-PK and CK2. In this review we consider how substrate phosphorylation together with BRCT domains, FHA domains and 14-3-3 proteins function to regulate ionizing radiation-induced nuclear foci and help to establish the G(2)/M checkpoint. We discuss the role of MDC1 a molecular scaffold that recruits early proteins to foci, such as NBS1 and RNF8, through distinct phosphodependent interactions. In addition, we consider the role of 14-3-3 proteins and the Chk2 FHA domain in initiating and maintaining cell cycle arrest.