Social interactions in digital environments: a study on fashion blogs based on Goffman

Este artigo pretende abordar algumas dinâmicas de interação socialexistentes em ambientes digitais a partir da análise de uma ferramenta midiáticaespecífica: os blogs de moda. Páginas virtuais com esse perfil ganharamexpressividade, proporcionando o desenvolvimento de uma dinâmica interacionalrelevante e despertando muitos comentários com os mais diversos objetivos.Essa expressividade contribuiu para que blogs de moda com audiências ativas enumerosas ganhassem relevância no campo da moda, indicando o poder dessasmídias na atualidade. Nesse sentido, novas agentes sociais surgem – as blogueirasde moda –, motivando dinâmicas interacionais específicas. Para compreenderessa dinâmica, serão usados alguns conceitos e estudos desenvolvidos pelo autorcanadense Erving Goffman.The article intends to address some social interaction dynamics thatexists in digital environments, from the analysis of a specific media tool: fashionblogs. Web pages with this profile won expressiveness, allowing the developmentof relevant interational dynamics, arousing several comments with the mostdiverse goals. This expressiveness contributed to fashion blogs – with active andnumerous visitors – gain relevance in the fashion field, even outside the web,indicating the power of these media nowadays. In this sense, new social actorsemerge – the fashion female bloggers – motivating specific and interactivedynamics. To understand this dynamics, we used some concepts and studiesdeveloped by the Canadian author Erving Goffman

Heterochromatic siRNAs and DDM1 Independently Silence Aberrant 5S rDNA Transcripts in Arabidopsis

5S ribosomal RNA gene repeats are arranged in heterochromatic arrays (5S rDNA) situated near the centromeres of Arabidopsis chromosomes. The chromatin remodeling factor DDM1 is known to maintain 5S rDNA methylation patterns while silencing transcription through 5S rDNA intergenic spacers (IGS). We mapped small-interfering RNAs (siRNA) to a composite 5S rDNA repeat, revealing a high density of siRNAs matching silenced IGS transcripts. IGS transcript repression requires proteins of the heterochromatic siRNA pathway, including RNA polymerase IV (Pol IV), RNA-DEPENDENT RNA POLYMERASE 2 (RDR2) and DICER-LIKE 3 (DCL3). Using molecular and cytogenetic approaches, we show that the DDM1 and siRNA-dependent silencing effects are genetically independent. DDM1 suppresses production of the siRNAs, however, thereby limiting RNA-directed DNA methylation at 5S rDNA repeats. We conclude that DDM1 and siRNA-dependent silencing are overlapping processes that both repress aberrant 5S rDNA transcription and contribute to the heterochromatic state of 5S rDNA arrays

BOLSA FAMÍLIA X SALÁRIO NA REPRODUÇÃO SOCIAL DE FAMÍLIAS POBRES EM BELÉM (PA)

Este artigo apresenta os principais resultados e análises, provenientes de uma dissertação concluída no ano de 2015, cujo objetivo foi o de compreender como as rendas do trabalho e do Programa Bolsa Família (PBF) se combinam ou se conflitam na reprodução social dos benefi ciários e se a percepção da renda do PBF os afastam do trabalho. O método adotado foi o crítico-dialético. Para isso, realiza uma pesquisa qualitativa, com a utilização de entrevistas semiestruturadas com benefi ciárias e trabalhadores do PBF de Belém (Pa). A principal conclusão do estudo é que as famílias estudadas tendem a combinar a renda proveniente de distintas formas de trabalho à renda do PBF no processo de reprodução social, preferindo a primeira, devido o valor moral atribuído e que as percepções do PBF oscilam entre o favor clientelista e o direito cidadão.Palavras-chave: Trabalho, Programa Bolsa Família, reprodução social

A concerted DNA methylation/histone methylation switch regulates rDNA gene dosage control and nucleolar dominance

Eukaryotes regulate the effective dosage of their ribosomal RNA (rRNA) genes, expressing fewer than half of the genes at any one time. Likewise, genetic hybrids displaying nucleolar dominance transcribe rRNA genes inherited from one parent but silence the other paraental set.We show that rRNA gene dosage control and nucleolar dominance utilize a common mechanis

The Arabidopsis Chromatin-Modifying Nuclear siRNA Pathway Involves a Nucleolar RNA Processing Center

SummaryIn Arabidopsis thaliana, small interfering RNAs (siRNAs) direct cytosine methylation at endogenous DNA repeats in a pathway involving two forms of nuclear RNA polymerase IV (Pol IVa and Pol IVb), RNA-DEPENDENT RNA POLYMERASE 2 (RDR2), DICER-LIKE 3 (DCL3), ARGONAUTE4 (AGO4), the chromatin remodeler DRD1, and the de novo cytosine methyltransferase DRM2. We show that RDR2, DCL3, AGO4, and NRPD1b (the largest subunit of Pol IVb) colocalize with siRNAs within the nucleolus. By contrast, Pol IVa and DRD1 are external to the nucleolus and colocalize with endogenous repeat loci. Mutation-induced loss of pathway proteins causes downstream proteins to mislocalize, revealing their order of action. Pol IVa acts first, and its localization is RNA dependent, suggesting an RNA template. We hypothesize that maintenance of the heterochromatic state involves locus-specific Pol IVa transcription followed by siRNA production and assembly of AGO4- and NRPD1b-containing silencing complexes within nucleolar processing centers

A DNA 3′ Phosphatase Functions in Active DNA Demethylation in Arabidopsis

DNA methylation is an important epigenetic mark established by the combined actions of methylation and demethylation reactions. Plants use a base excision repair pathway for active DNA demethylation. After 5-methylcytosine removal, the Arabidopsis DNA glycosylase/lyase ROS1 incises the DNA backbone and part of the product has a single-nucleotide gap flanked by 3′- and 5′-phosphate termini. Here we show that the DNA phosphatase ZDP removes the blocking 3′ phosphate, allowing subsequent DNA polymerization and ligation steps needed to complete the repair reactions. ZDP and ROS1 interact in vitro and colocalize in vivo in nucleoplasmic foci. Extracts from zdp mutant plants are unable to complete DNA demethylation in vitro, and the mutations cause DNA hypermethylation and transcriptional silencing of a reporter gene. Genome-wide methylation analysis in zdp mutant plants identified hundreds of hypermethylated endogenous loci. Our results show that ZDP functions downstream of ROS1 in one branch of the active DNA demethylation pathway

DNA Topoisomerase 1α Promotes Transcriptional Silencing of Transposable Elements through DNA Methylation and Histone Lysine 9 Dimethylation in Arabidopsis

RNA-directed DNA methylation (RdDM) and histone H3K9 dimethylation (H3K9me2) are related transcriptional silencing mechanisms that target transposable elements (TEs) and repeats to maintain genome stability in plants. RdDM is mediated by small and long noncoding RNAs produced by the plant-specific RNA polymerases Pol IV and Pol V, respectively. Through a chemical genetics screen with a luciferase-based DNA methylation reporter, LUCL, we found that camptothecin, a compound with anti- cancer properties that targets DNA topoisomerase 1α (TOP1α) was able to de-repress LUCL by reducing its DNA methylation and H3K9me2 levels. Further studies with Arabidopsis top1α mutants showed that TOP1α silences endogenous RdDM loci by facilitating the production of Pol V-dependent long non-coding RNAs, AGONAUTE4 recruitment and H3K9me2 deposition at TEs and repeats. This study assigned a new role in epigenetic silencing to an enzyme that affects DNA topology.Fil: Dinh, Thanh Theresa. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados Unidos. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology. ChemGen IGERT program; Estados UnidosFil: Gao, Lei. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: Liu, Xigang . University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: Li, Dongming. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados Unidos. Lanzhou University. School of Life Sciences Plant Biology Laboratory; ChinaFil: Li, Shengben. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: Zhao, Yuanyuan. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: O'leary, Michael. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: Le, Brandon. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: Schmitz, Robert J.. The Salk Institute for Biological Studies. Plant Biology Laboratory; Estados UnidosFil: Manavella, Pablo Andrés. Max Planck Institute for Developmental Biology. Department of Molecular Biology; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Agrobiotecnologia del Litoral; ArgentinaFil: Li, Shaofang. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados UnidosFil: Weigel, Detlef. Max Planck Institute for Developmental Biology. Department of Molecular Biology; AlemaniaFil: Pontes, Olga. University of New Mexico. Department of Biology; Estados UnidosFil: Ecker, Joseph R.. The Salk Institute for Biological Studies. Howard Hughes Medical Institute; Estados Unidos. The Salk Institute for Biological Studies. Plant Biology Laboratory; Estados UnidosFil: Chen, Xuemei. University of California Riverside. Center for Plant Cell Biology, Institute of Integrative Genome Biology, Department of Botany and Plant Sciences; Estados Unidos. University of California Riverside. Howard Hughes Medical Institute, ; Estados Unido

A subgroup of SGS3-like proteins act redundantly in RNA-directed DNA methylation

Plant specific SGS3-like proteins are composed of various combinations of an RNA-binding XS domain, a zinc-finger zf-XS domain, a coil–coil domain and a domain of unknown function called XH. In addition to being involved in de novo 2 (IDN2) and SGS3, the Arabidopsis genome encodes 12 uncharacterized SGS3-like proteins. Here, we show that a group of SGS3-like proteins act redundantly in RNA-directed DNA methylation (RdDM) pathway in Arabidopsis. Transcriptome co-expression analyses reveal significantly correlated expression of two SGS3-like proteins, factor of DNA methylation 1 (FDM1) and FDM2 with known genes required for RdDM. The fdm1 and fdm2 double mutations but not the fdm1 or fdm2 single mutations significantly impair DNA methylation at RdDM loci, release transcriptional gene silencing and dramatically reduce the abundance of siRNAs originated from high copy number repeats or transposons. Like IDN2 and SGS3, FDM1 binds dsRNAs with 5′ overhangs. Double mutant analyses also reveal that IDN2 and three uncharacterized SGS3-like proteins FDM3, FDM4 and FDM5 have overlapping function with FDM1 in RdDM. Five FDM proteins and IDN2 define a group of SGS3-like proteins that possess all four-signature motifs in Arabidopsis. Thus, our results demonstrate that this group of SGS3-like proteins is an important component of RdDM. This study further enhances our understanding of the SGS3 gene family and the RdDM pathway

Postembryonic establishment of megabase-scale gene silencing in nucleolar dominance

Nucleolar dominance is an epigenetic phenomenon in plant and animal genetic hybrids that describes the expression of 45S ribosomal RNA genes (rRNA genes) inherited from only one progenitor due to the silencing of the other progenitor’s rRNA genes. rRNA genes are tandemly arrayed at nucleolus organizer regions (NORs) that span millions of basepairs, thus gene silencing in nucleolar dominance occurs on a scale second only to X-chromosome inactivation in female mammals. In Arabidopsis suecica, the allotetraploid hybrid of A. thaliana and A. arenosa, theA. thaliana –derived rRNA genes are subjected to nucleolar dominance and are silenced via repressive chromatin modifications. However, the developmental stage at which nucleolar dominance is established in A. suecica is currently unknown. We show that nucleolar dominance is not apparent in seedling cotyledons formed during embryogenesis but becomes progressively established during early postembryonic development in tissues derived from both the shoot and root apical meristems. The progressive silencing of A. thaliana rRNA genes correlates with the transition of A. thaliana NORs from a decondensed euchromatic state associated with histone H3 that is trimethylated on lysine 4 (H3K4me3) to a highly condensed heterochromatic state in which the NORs are associated with H3K9me2 and 5-methylcytosine-enriched chromocenters. In RNAi-lines in which the histone deacetylases HDA6 and HDT1 are knocked down, the developmentally regulated condensation and inactivation of A. thaliana NORs is disrupted. Collectively, these data demonstrate that HDA6 and HDT1 function in the postembryonic establishment of nucleolar dominance, a process which recurs in each generatio