Structural snapshots of R-loop formation by a type I-C CRISPR Cascade.

Type I CRISPR-Cas systems employ multi-subunit Cascade effector complexes to target foreign nucleic acids for destruction. Here, we present structures of D. vulgaris type I-C Cascade at various stages of double-stranded (ds)DNA target capture, revealing mechanisms that underpin PAM recognition and Cascade allosteric activation. We uncover an interesting mechanism of non-target strand (NTS) DNA stabilization via stacking interactions with the "belly" subunits, securing the NTS in place. This "molecular seatbelt" mechanism facilitates efficient R-loop formation and prevents dsDNA reannealing. Additionally, we provide structural insights into how two anti-CRISPR (Acr) proteins utilize distinct strategies to achieve a shared mechanism of type I-C Cascade inhibition by blocking PAM scanning. These observations form a structural basis for directional R-loop formation and reveal how different Acr proteins have converged upon common molecular mechanisms to efficiently shut down CRISPR immunity.

Access to nutrition advice and knowledge, attitudes and practices of pregnant women in Ireland: A cross-sectional study.

BACKGROUND: Healthy nutritional status, appropriate gestational weight gain and a balanced diet are important predictors of perinatal health outcomes. However, gaps exist in the translation of nutrition recommendations into dietary practices of women before and during pregnancy. The present study explored the relationship between access to nutrition advice, nutrition knowledge, attitudes and practices among pregnant women. METHODS: Pregnant women aged > 18 years in Ireland were eligible to complete a self-administered survey consisting of four subsections (demographics, nutrition knowledge, attitudes and practices) delivered online through Qualtrics. RESULTS: In this convenience sample (n = 334, median [interquartile range] gestation, 25.0 [16.0, 34.0] weeks), 85% had at least an honours bachelor degree and 88.9% planned their pregnancy. Two out of five women received nutrition advice during their pregnancy, mostly from a midwife. Based on the percentage of correct answers (of 15 questions), women with previous nutrition education (e.g., school home economics) had better median [interquartile range] nutrition knowledge than those with none (80.0% [66.7, 86.7%] vs. 73.3% [60.0, 80.0%], p < 0.001). Those who received nutrition advice during pregnancy did not score higher than those who did not (73.3% [66.7, 80.0%] vs. 73.3% [66.7, 80.0%], p = 0.6). Over three-quarters of participants considered nutritional supplement use to be very or extremely important. Although 73.6% and 92.4% took supplements prior to and during pregnancy, only 25.7% reported compliance with periconceptional folic acid supplementation guidelines. Half of respondents considered healthy eating during pregnancy as very or extremely important. CONCLUSIONS: Access to nutrition advice during pregnancy was inadequate with poor nutrition knowledge, attitudes and practices observed. Accessible, evidence-based nutrition education for women prior to and during pregnancy is required.

Structural basis for assembly of non-canonical small subunits into type I-C Cascade.

Bacteria and archaea employ CRISPR (clustered, regularly, interspaced, short palindromic repeats)-Cas (CRISPR-associated) systems as a type of adaptive immunity to target and degrade foreign nucleic acids. While a myriad of CRISPR-Cas systems have been identified to date, type I-C is one of the most commonly found subtypes in nature. Interestingly, the type I-C system employs a minimal Cascade effector complex, which encodes only three unique subunits in its operon. Here, we present a 3.1 Å resolution cryo-EM structure of the Desulfovibrio vulgaris type I-C Cascade, revealing the molecular mechanisms that underlie RNA-directed complex assembly. We demonstrate how this minimal Cascade utilizes previously overlooked, non-canonical small subunits to stabilize R-loop formation. Furthermore, we describe putative PAM and Cas3 binding sites. These findings provide the structural basis for harnessing the type I-C Cascade as a genome-engineering tool.