The trans-activation domain of the sporulation response regulator Spo0A revealed by X-ray crystallography

Sporulation in Bacillus involves the induction of scores of genes in a temporally and spatially co-ordinated programme of cell development. Its initiation is under the control of an expanded two-component signal transduction system termed a phosphorelay. The master control element in the decision to sporulate is the response regulator, Spo0A, which comprises a receiver or phosphoacceptor domain and an effector or transcription activation domain. The receiver domain of Spo0A shares sequence similarity with numerous response regulators, and its structure has been determined in phosphorylated and unphosphorylated forms. However, the effector domain (C-Spo0A) has no detectable sequence similarity to any other protein, and this lack of structural information is an obstacle to understanding how DNA binding and transcription activation are controlled by phosphorylation in Spo0A. Here, we report the crystal structure of C-Spo0A from Bacillus stearothermophilus revealing a single alpha -helical domain comprising six alpha -helices in an unprecedented fold. The structure contains a helix-turn-helix as part of a three alpha -helical bundle reminiscent of the catabolite gene activator protein (CAP), suggesting a mechanism for DNA binding. The residues implicated in forming the sigma (A)-activating region clearly cluster in a flexible segment of the polypeptide on the opposite side of the structure from that predicted to interact with DNA. The structural results are discussed in the context of the rich array of existing mutational data

Genetic analysis of the large subunit of yeast transcription factor IIE reveals two regions with distinct functions.

Biochemical analysis of proteins necessary for transcription initiation by eukaryotic RNA polymerase II (pol II) has identified transcription factor IIE (TFIIE) as an essential component of the reaction. To better understand the role of TFIIE in transcription, we isolated conditional alleles of TFA1, the gene encoding the large subunit of TFIIE in the yeast Saccharomyces cerevisiae. The mutant Tfa1 proteins fall into two classes. The first class causes thermosensitive growth due to single amino acid substitutions of the cysteines comprising the Zn-binding motif. The second mutant class is made up of proteins that are C-terminally truncated and that cause a cold-sensitive growth phenotype. The behavior of these mutants suggests that Tfa1p possesses at least two domains with genetically distinct functions. The mutations in the Zn-binding motif do not affect the mutant protein's stability at the nonpermissive temperature or its ability to associate with the small subunit of TFIIE. Our studies further determined that wild-type TFIIE can bind to single-stranded DNA in vitro. However, this property is unaffected in the mutant TFIIE complexes. Finally, we have demonstrated the biological importance of TFIIE in pol II-mediated transcription by depleting the Tfa1 protein from the cells and observing a concomitant decrease in total poly(A)+ mRNA

Introducing Pre-university Students to Primary Scientific Literature Through Argumentation Analysis

<p>Primary scientific literature is one of the most important means of communication in science, written for peers in the scientific community. Primary literature provides an authentic context for showing students how scientists support their claims. Several teaching strategies have been proposed using (adapted) scientific publications, some for secondary education, but none of these strategies focused specifically on scientific argumentation. The purpose of this study is to evaluate a strategy for teaching pre-university students to read unadapted primary scientific literature, translated into students' native language, based on a new argumentation analysis framework. This framework encompasses seven types of argumentative elements: motive, objective, main conclusion, implication, support, counterargument and refutation. During the intervention, students studied two research articles. We monitored students' reading comprehension and their opinion on the articles and activities. After the intervention, we measured students' ability to identify the argumentative elements in a third unadapted and translated research article. The presented framework enabled students to analyse the article by identifying the motive, objective, main conclusion and implication and part of the supports. Students stated that they found these activities useful. Most students understood the text on paragraph level and were able to read the article with some help for its vocabulary. We suggest that primary scientific literature has the potential to show students important aspects of the scientific process and to learn scientific vocabulary in an authentic context.</p>

Transcriptional activation by recruitment

The recruitment model for gene activation stipulates that an activator works by bringing the transcriptional machinery to the DNA. Recent experiments in bacteria and yeast indicate that many genes can be activated by this mechanism. These findings have implications for our understanding of the nature of activating regions and their targets, and for the role of histones in gene regulation