SAGA Is a General Cofactor for RNA Polymerase II Transcription

Prior studies suggested that SAGA and TFIID are alternative factors that promote RNA polymerase II transcription, with about 10% of genes in S. cerevisiae dependent on SAGA. We reassessed the role of SAGA by mapping its genome-wide location and role in global transcription in budding yeast. We find that SAGA maps to the UAS elements of most genes, overlapping with Mediator binding and irrespective of previous designations of SAGA- or TFIID-dominated genes. Disruption of SAGA through mutation or rapid subunit depletion reduces transcription from nearly all genes, measured by newly synthesized RNA. We also find that the acetyltransferase Gcn5 synergizes with Spt3 to promote global transcription and that Spt3 functions to stimulate TBP recruitment at all tested genes. Our data demonstrate that SAGA acts as a general cofactor required for essentially all RNA polymerase II transcription and is not consistent with the previous classification of SAGA- and TFIID-dominated genes. Baptista et al. show that SAGA, a transcriptional coactivator conserved in all eukaryotes, is involved in overall RNA polymerase II transcription in budding yeast. Using ChEC-seq, SAGA was shown to be recruited to both TATA-containing and TATA-less genes. In agreement, inactivation of SAGA leads to dramatic effects on nascent transcription

Detection of siderophores in endophytic bacteria Methylobacterium spp. associated with Xylella fastidiosa subsp. pauca Detecção de sideróforos nas bactérias endofíticas Methylobacterium spp. associadas com Xylella fastidiosa subsp. pauca

The objective of this work was to study the production of siderophores by endophytic bacteria Methylobacterium spp., which occupy the same ecological niche as Xylella fastidiosa subsp. pauca (Xfp) in citrus plants. The siderophore production of Methylobacterium strains was tested according to chromeazurol agar assay test (CAS), Csáky test (hydroxamate-type) and Arnow test (catechol-type). In addition, the ability of Xfp to use siderophores, in vitro, produced by endophytic bacteria as source of iron, was evaluated. All 37 strains of Methylobacterium spp. tested were CAS-positive for siderophore production. Methylobacterium spp. produced hydroxamate-type, but not catechol-type siderophores. In vitro growth of Xfp was stimulated by the presence of supernatant siderophores of endophytic Methylobacterium mesophilicum.<br>O objetivo deste trabalho foi estudar a produção de sideróforos pelas bactérias endofíticas Methylobacterium spp., que ocupam o mesmo nicho ecológico que Xylella fastidiosa subsp. pauca (Xfp), em plantas cítricas. A produção de sideróforos, pelas linhagens de Methylobacterium, foi testada por meio do ensaio de cromoazarol-ágar (chromeazurol agar assay-CAS), teste de Csáky (tipo hidroxamato) e do teste de Arnow (tipo catecol). Além disso, a habilidade de Xfp em utilizar sideróforos produzidos por bactérias endofíticas, como fonte de ferro, in vitro, foi avaliada. Todas as 37 linhagens de Methylobacterium spp. testadas foram positivas para a produção de sideróforos, pelo teste CAS-ágar. Methylobacterium spp. foram capazes de produzir sideróforos do tipo hidroxamato, mas não do tipo catecol. O crescimento in vitro de Xfp foi estimulado pela presença de sideróforos no sobrenadante de Methylobacterium mesophilicum endofítica

De Novo Heterozygous POLR2A Variants Cause a Neurodevelopmental Syndrome with Profound Infantile-Onset Hypotonia

The RNA polymerase II complex (pol II) is responsible for transcription of all ∼21,000 human protein-encoding genes. Here, we describe sixteen individuals harboring de novo heterozygous variants in POLR2A, encoding RPB1, the largest subunit of pol II. An iterative approach combining structural evaluation and mass spectrometry analyses, the use of S. cerevisiae as a model system, and the assessment of cell viability in HeLa cells allowed us to classify eleven variants as probably disease-causing and four variants as possibly disease-causing. The significance of one variant remains unresolved. By quantification of phenotypic severity, we could distinguish mild and severe phenotypic consequences of the disease-causing variants. Missense variants expected to exert only mild structural effects led to a malfunctioning pol II enzyme, thereby inducing a dominant-negative effect on gene transcription. Intriguingly, individuals carrying these variants presented with a severe phenotype dominated by profound infantile-onset hypotonia and developmental delay. Conversely, individuals carrying variants expected to result in complete loss of function, thus reduced levels of functional pol II from the normal allele, exhibited the mildest phenotypes. We conclude that subtle variants that are central in functionally important domains of POLR2A cause a neurodevelopmental syndrome characterized by profound infantile-onset hypotonia and developmental delay through a dominant-negative effect on pol-II-mediated transcription of DNA