RESUMO
E6AP dysfunction is associated with Angelman syndrome and Autism spectrum disorder. Additionally, the host E6AP is hijacked by the high-risk HPV E6 to aberrantly ubiquitinate the tumor suppressor p53, which is linked with development of multiple types of cancer, including most cervical cancers. Here we show that E6AP and the E6AP/E6 complex exist, respectively, as a monomer and a dimer of the E6AP/E6 protomer. The short α1-helix of E6AP transforms into a longer helical structure when in complex with E6. The extended α1-helices of the dimer intersect symmetrically and contribute to the dimerization. The two protomers sway around the crossed region of the two α1-helices to promote the attachment and detachment of substrates to the catalytic C-lobe of E6AP, thus facilitating ubiquitin transfer. These findings, complemented by mutagenesis analysis, suggest that the α1-helix, through conformational transformations, controls the transition between the inactive monomer and the active dimer of E6AP.
Assuntos
Multimerização Proteica , Ubiquitina-Proteína Ligases , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/genética , Humanos , Ubiquitina/metabolismo , Ubiquitina/química , Ubiquitinação , Modelos Moleculares , Cristalografia por Raios X , Proteínas Oncogênicas Virais/metabolismo , Proteínas Oncogênicas Virais/química , Proteínas Oncogênicas Virais/genética , Proteína Supressora de Tumor p53/metabolismo , Proteína Supressora de Tumor p53/química , Proteína Supressora de Tumor p53/genética , Ligação Proteica , Conformação Proteica em alfa-HéliceRESUMO
The portal-scaffold complex is believed to nucleate the assembly of herpesvirus procapsids. During capsid maturation, two events occur: scaffold expulsion and DNA incorporation. The portal-scaffold interaction and the conformational changes that occur to the portal during the different stages of capsid formation have yet to be elucidated structurally. Here we present high-resolution structures of the A- and B-capsids and in-situ portals of human cytomegalovirus. We show that scaffolds bind to the hydrophobic cavities formed by the dimerization and Johnson-fold domains of the major capsid proteins. We further show that 12 loop-helix-loop fragments-presumably from the scaffold domain-insert into the hydrophobic pocket of the portal crown domain. The portal also undergoes significant changes both positionally and conformationally as it accompanies DNA packaging. These findings unravel the mechanism by which the portal interacts with the scaffold to nucleate capsid assembly and further our understanding of scaffold expulsion and DNA incorporation.
Assuntos
Capsídeo , Herpesvirus Humano 1 , Humanos , Capsídeo/metabolismo , Microscopia Crioeletrônica , Citomegalovirus/genética , Proteínas Virais/metabolismo , Herpesvirus Humano 1/genética , Montagem de Vírus/genética , Proteínas do Capsídeo/metabolismo , DNA/metabolismoRESUMO
BACKGROUND: Three NBS-LRR genes, Rpi-blb2, Mi-1.2, and Cami, constitute a very special plant resistance gene family. These genes confer resistance against 4 distantly related pathogen species in 3 different Solanaceae hosts. To characterize this noted resistance, we conducted a series of studies on this gene family. RESULTS: First, homologs of this gene family were identified in the pepper, tomato and potato genomes. This revealed a large variation in copy number within this gene family among species and a great divergence was found both between and within species. To gain more information pertaining to gene resistance within this family, 121 LRR regions were cloned in 16 different wild/cultivated potato accessions. Again, frequent copy number variations and a high level of divergence between homolog were observed common among accessions. The divergence within species was so high that it reaches the level of divergence between species. Also, frequent frameshift mutations and abundant gene conversion events were identified in these LRR regions. CONCLUSIONS: Our findings suggest that this family harbors an unusually high level of genetic abundance, making it of particular interest. Together with other reported examples, our study also provides evidence that multi-resistance is a common trait in R gene families like this.
Assuntos
Genes de Plantas , Doenças das Plantas/genética , Doenças das Plantas/imunologia , Solanaceae/genética , Solanaceae/imunologia , Variações do Número de Cópias de DNA , Variação Genética , Filogenia , Phytophthora infestans/fisiologia , Doenças das Plantas/parasitologia , Solanaceae/classificação , Solanaceae/parasitologiaRESUMO
Late blight caused by the oomycete Phytophthora infestans is one of the most severe threats to potato production worldwide. Numerous studies suggest that the most effective protective strategy against the disease would be to provide potato cultivars with durable resistance (R) genes. However, little is known about the origin and evolutional history of these durable R-genes in potato. Addressing this might foster better understanding of the dynamics of these genes in nature and provide clues for identifying potential candidate R-genes. Here, a systematic survey was executed at RB/Rpi-blb1 locus, an exclusive broad-spectrum R-gene locus in potato. As indicated by synteny analysis, RB/Rpi-blb1 homologs were identified in all tested genomes, including potato, tomato, pepper, and Nicotiana, suggesting that the RB/Rpi-blb1 locus has an ancient origin. Two evolutionary patterns, similar to those reported on RGC2 in Lactuca, and Pi2/9 in rice, were detected at this locus. Type I RB/Rpi-blb1 homologs have frequent copy number variations and sequence exchanges, obscured orthologous relationships, considerable nucleotide divergence, and high non-synonymous to synonymous substitutions (Ka/Ks) between or within species, suggesting rapid diversification and balancing selection in response to rapid changes in the oomycete pathogen genomes. These characteristics may serve as signatures for cloning of late blight resistance genes.
