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The to and fro of RNA polymerase RNA polymerase II (RNA pol II) moves forwards along the DNA strand during gene transcription, synthesizing messenger RNA as it goes. It can also move backwards and stall — a useful property for regulatory purposes or if it hits an obstacle such as a nucleosome. This arrested state is reactivated by transcription factor IIS (TFIIS). Now, the crystal structure of a backtracked yeast RNA pol II complex containing observable backtracked RNA has been determined at 3.3 Å resolution, as well as the structure of a backtracked complex containing TFIIS. The structures reveal possible mechanisms of transcriptional stalling and transcription reactivation. During gene transcription, RNA polymerase (Pol) II moves forward along DNA and synthesizes mRNA. However, Pol II can also move backwards and stall, which is important for regulatory purposes or when the polymerase hits an obstacle such as a nucleosome. This arrested state is reactivated by the transcription factor TFIIS. Here, a crystal structure is presented of a backtracked yeast Pol II complex in which the backtracked RNA can be observed, plus a structure of a backtracked complex that contains TFIIS. A model is presented for Pol II backtracking, arrest and reactivation during transcription elongation. During gene transcription, RNA polymerase (Pol) II moves forwards along DNA and synthesizes messenger RNA. However, at certain DNA sequences, Pol II moves backwards, and such backtracking can arrest transcription. Arrested Pol II is reactivated by transcription factor IIS (TFIIS), which induces RNA cleavage that is required for cell viability 1 . Pol II arrest and reactivation are involved in transcription through nucleosomes 2 , 3 and in promoter-proximal gene regulation 4 , 5 , 6 . Here we present X-ray structures at 3.3 Å resolution of an arrested Saccharomyces cerevisiae Pol II complex with DNA and RNA, and of a reactivation intermediate that additionally contains TFIIS. In the arrested complex, eight nucleotides of backtracked RNA bind a conserved ‘backtrack site’ in the Pol II pore and funnel, trapping the active centre trigger loop and inhibiting mRNA elongation. In the reactivation intermediate, TFIIS locks the trigger loop away from backtracked RNA, displaces RNA from the backtrack site, and complements the polymerase active site with a basic and two acidic residues that may catalyse proton transfers during RNA cleavage. The active site is demarcated from the backtrack site by a ‘gating tyrosine’ residue that probably delimits backtracking. These results establish the structural basis of Pol II backtracking, arrest and reactivation, and provide a framework for analysing gene regulation during transcription elongation.

Gene transcription by RNA polymerase II is regulated by activator proteins that recruit the coactivator complexes SAGA (Spt–Ada–Gcn5–acetyltransferase) 1 , 2 and transcription factor IID (TFIID) 2 – 4 . SAGA is required for all regulated transcription 5 and is conserved among eukaryotes 6 . SAGA contains four modules 7 – 9 : the activator-binding Tra1 module, the core module, the histone acetyltransferase (HAT) module and the histone deubiquitination (DUB) module. Previous studies provided partial structures 10 – 14 , but the structure of the central core module is unknown. Here we present the cryo-electron microscopy structure of SAGA from the yeast Saccharomyces cerevisiae and resolve the core module at 3.3 Å resolution. The core module consists of subunits Taf5, Sgf73 and Spt20, and a histone octamer-like fold. The octamer-like fold comprises the heterodimers Taf6–Taf9, Taf10–Spt7 and Taf12–Ada1, and two histone-fold domains in Spt3. Spt3 and the adjacent subunit Spt8 interact with the TATA box-binding protein (TBP) 2 , 7 , 15 – 17 . The octamer-like fold and its TBP-interacting region are similar in TFIID, whereas Taf5 and the Taf6 HEAT domain adopt distinct conformations. Taf12 and Spt20 form flexible connections to the Tra1 module, whereas Sgf73 tethers the DUB module. Binding of a nucleosome to SAGA displaces the HAT and DUB modules from the core-module surface, allowing the DUB module to bind one face of an ubiquitinated nucleosome. Structural studies on the yeast transcription coactivator complex SAGA (Spt–Ada–Gcn5–acetyltransferase) provide insights into the mechanism of initiation of regulated transcription by this multiprotein complex, which is conserved among eukaryotes.

Previous reviews have synthesized the impacts of universal school-based social emotional learning (SEL) programs. However, they have yet to attempt a meta-analytic approach with rigorous inclusion criteria to identify the key SEL components and explore what make these programs work. This study aims to fill that gap by examining the impacts of SEL programs and exploring the moderating effects of methodological characteristics, implementation features, and program components on SEL effectiveness. The final sample consisted of 12 high-quality SEL programs, 59 studies, and 83,233 participants, with an overall effect size of 0.15. Meta-regression results indicated that these SEL programs could significantly improve youth social emotional skills, reinforce affect and attitudes, promote academic performance, increase prosocial behaviors, and reduce antisocial behaviors. Training teachers’ social emotional skills and reducing cognitive elements in SEL curricula were found to be effective components of SEL programs, whereas pedagogical activities, climate support, and family engagement were not. Large-scale studies of SEL programs tended to generate smaller effect sizes, and those with low program dosages were found to be less effective than those approaching the recommended dosage. Policy and practical implications on how to scale SEL programs are discussed.

As evidence becomes increasingly important in educational policy, it is essential to understand how research design might contribute to reported effect sizes in experiments evaluating educational programs. A total of 645 studies from 12 recent reviews of evaluations of preschool, reading, mathematics, and science programs were studied. Effect sizes were roughly twice as large for published articles, small-scale trials, and experimenter-made measures, compared to unpublished documents, large-scale studies, and independent measures, respectively. Effect sizes were significantly higher in quasiexperiments than in randomized experiments. Excluding tutoring studies, there were no significant differences in effect sizes between elementary and middle/high studies. Regression analyses found that effects of all factors maintained after controlling for all other factors. Explanations for the effects of methodological features on effect sizes are discussed, as are implications for evidence-based policy.

NuA4 is a highly conserved histone acetyltransferase complex that functions in transcription and DNA repair. Four groups have recently determined the structure of NuA4 from two different yeasts using cryo-EM, revealing important mechanistic details of its function and allowing a detailed comparison to the related SAGA complex.

COPII mediates Endoplasmic Reticulum to Golgi trafficking of thousands of cargoes. Five essential proteins assemble into a two-layer architecture, with the inner layer thought to regulate coat assembly and cargo recruitment, and the outer coat forming cages assumed to scaffold membrane curvature. Here we visualise the complete, membrane-assembled COPII coat by cryo-electron tomography and subtomogram averaging, revealing the full network of interactions within and between coat layers. We demonstrate the physiological importance of these interactions using genetic and biochemical approaches. Mutagenesis reveals that the inner coat alone can provide membrane remodelling function, with organisational input from the outer coat. These functional roles for the inner and outer coats significantly move away from the current paradigm, which posits membrane curvature derives primarily from the outer coat. We suggest these interactions collectively contribute to coat organisation and membrane curvature, providing a structural framework to understand regulatory mechanisms of COPII trafficking and secretion. Cytosolic coat proteins capture secretory cargo and sculpt membrane carriers for intracellular transport, such as COPII which mediates Endoplasmic Reticulum to Golgi trafficking of thousands of cargoes. Here authors visualise the complete, membrane-assembled COPII coat by cryo-electron tomography and subtomogram averaging, revealing the full network of interactions within and between coat layers.

Related RNA polymerases (RNAPs) carry out cellular gene transcription in all three kingdoms of life. The universal conservation of the transcription machinery extends to a single RNAP‐associated factor, Spt5 (or NusG in bacteria), which renders RNAP processive and may have arisen early to permit evolution of long genes. Spt5 associates with Spt4 to form the Spt4/5 heterodimer. Here, we present the crystal structure of archaeal Spt4/5 bound to the RNAP clamp domain, which forms one side of the RNAP active centre cleft. The structure revealed a conserved Spt5–RNAP interface and enabled modelling of complexes of Spt4/5 counterparts with RNAPs from all kingdoms of life, and of the complete yeast RNAP II elongation complex with bound Spt4/5. The N‐terminal NGN domain of Spt5/NusG closes the RNAP active centre cleft to lock nucleic acids and render the elongation complex stable and processive. The C‐terminal KOW1 domain is mobile, but its location is restricted to a region between the RNAP clamp and wall above the RNA exit tunnel, where it may interact with RNA and/or other factors. Spt5 and NusG play a conserved role in stimulating RNA polymerase II transcription elongation and processivity. Here, the crystal structure of Spt4/5 bound to the RNA polymerase clamp domain reveals that the factor binds above DNA and RNA in the active centre cleft preventing premature dissociation of the polymerase.

Eukaryotic origin firing depends on assembly of the Cdc45-MCM-GINS (CMG) helicase. A key step is the recruitment of GINS that requires the leading-strand polymerase Pol epsilon, composed of Pol2, Dpb2, Dpb3, Dpb4. While a truncation of the catalytic N-terminal Pol2 supports cell division, Dpb2 and C-terminal Pol2 (C-Pol2) are essential for viability. Dpb2 and C-Pol2 are non-catalytic modules, shown or predicted to be related to an exonuclease and DNA polymerase, respectively. Here, we present the cryo-EM structure of the isolated C-Pol2/Dpb2 heterodimer, revealing that C-Pol2 contains a DNA polymerase fold. We also present the structure of CMG/C-Pol2/Dpb2 on a DNA fork, and find that polymerase binding changes both the helicase structure and fork-junction engagement. Inter-subunit contacts that keep the helicase-polymerase complex together explain several cellular phenotypes. At least some of these contacts are preserved during Pol epsilon-dependent CMG assembly on path to origin firing, as observed with DNA replication reconstituted in vitro. Eukaryotic origin firing depends on assembly of the Cdc45-MCM-GINS (CMG) helicase, which requires the leading-strand polymerase Pol ɛ. Here the authors present a structural analysis of a CMG Pol ɛ on a DNA fork, providing insight on the steps leading productive helicase engagement to the DNA junction.

As learners are able to perceive interactivity when interacting with instructors or peer learners in traditional learning environments, learners are similarly able to perceive interactivity when interacting with artificial intelligence (AI) in AI-supported learning environments. Advancements in AI, such as generative AI including ChatGPT and Midjourney, enhance learners’ perceived interactivity, thereby facilitating learning through AI-enabled interaction. However, there is no scale in education for measuring perceived interactivity of learner-AI interaction. This study develops a 17-item scale to assess the extent to which a learner perceives interactivity with AI from four dimensions: responsiveness, personalization, learner control, and learning engagement. The sample group included 422 Chinese university students for the first application and 306 university students for the second application. Both the exploratory factor analysis and the confirmatory factor analysis verified the factor structure of the scale. The Cronbach’s alpha value for the whole scale was 0.948, whereas the Cronbach’s alpha values for the four dimensions ranged between 0.820 and 0.915. Results suggested that this scale was a reliable and valid instrument. This study also found that perceived interactivity of learner-AI interaction was significantly associated with AI tools, learners’ behavioral intentions to use AI in learning, months of using AI in learning, and average duration of using AI in learning each time, and not associated with ages, genders, education levels, and fields of education. Finally, theoretical and practical implications are discussed.

Transcription of ribosomal RNA by RNA polymerase (Pol) I initiates ribosome biogenesis and regulates eukaryotic cell growth. The crystal structure of Pol I from the yeast Saccharomyces cerevisiae at 2.8 Å resolution reveals all 14 subunits of the 590-kilodalton enzyme, and shows differences to Pol II. An ‘expander’ element occupies the DNA template site and stabilizes an expanded active centre cleft with an unwound bridge helix. A ‘connector’ element invades the cleft of an adjacent polymerase and stabilizes an inactive polymerase dimer. The connector and expander must detach during Pol I activation to enable transcription initiation and cleft contraction by convergent movement of the polymerase ‘core’ and ‘shelf’ modules. Conversion between an inactive expanded and an active contracted polymerase state may generally underlie transcription. Regulatory factors can modulate the core–shelf interface that includes a ‘composite’ active site for RNA chain initiation, elongation, proofreading and termination. The crystal structure of the complete 14-subunit RNA polymerase (Pol) I from yeast is determined, providing insights into its unique architecture and the possible functional roles of its components. Pol I structure determined RNA polymerase I (Pol I) transcribes ribosomal RNA which is critically required for ribosome assembly, and the enzyme is therefore a major determinant of protein biosynthesis and cell growth. Mis-regulation of Pol I has been associated with several types of cancer, and Pol I is an emerging target for anticancer drugs. In this issue of Nature , two groups, working independently, present the X-ray crystal structure of the complete 14-subunit Pol I from yeast, determined at 3.0 Å and 2.8 Å resolution. The basic architecture of Pol I resembles those of Pol II and Pol III, but its DNA-binding cleft adopts a wider conformation than seen in the other RNA polymerases, and other unique features also provide insights into the functional roles of its components.