Which yeast species shall I choose? Saccharomyces cerevisiae versus Pichia pastoris (review)

Having decided on yeast as a production host, the choice of species is often the first question any researcher new to the field will ask. With over 500 known species of yeast to date, this could pose a significant challenge. However, in reality, only very few species of yeast have been employed as host organisms for the production of recombinant proteins. The two most widely used, Saccharomyces cerevisiae and Pichia pastoris, are compared and contrasted here

Understanding the yeast host cell response to recombinant membrane protein production

Membrane proteins are drug targets for a wide range of diseases. Having access to appropriate samples for further research underpins the pharmaceutical industry's strategy for developing new drugs. This is typically achieved by synthesizing a protein of interest in host cells that can be cultured on a large scale, allowing the isolation of the pure protein in quantities much higher than those found in the protein's native source. Yeast is a popular host as it is a eukaryote with similar synthetic machinery to that of the native human source cells of many proteins of interest, while also being quick, easy and cheap to grow and process. Even in these cells, the production of human membrane proteins can be plagued by low functional yields; we wish to understand why. We have identified molecular mechanisms and culture parameters underpinning high yields and have consolidated our findings to engineer improved yeast host strains. By relieving the bottlenecks to recombinant membrane protein production in yeast, we aim to contribute to the drug discovery pipeline, while providing insight into translational processes

Evaluating the Effects of SARS-CoV-2 Spike Mutation D614G on Transmissibility and Pathogenicity

Global dispersal and increasing frequency of the SARS-CoV-2 spike protein variant D614G are suggestive of a selective advantage but may also be due to a random founder effect. We investigate the hypothesis for positive selection of spike D614G in the United Kingdom using more than 25,000 whole genome SARS-CoV-2 sequences. Despite the availability of a large dataset, well represented by both spike 614 variants, not all approaches showed a conclusive signal of positive selection. Population genetic analysis indicates that 614G increases in frequency relative to 614D in a manner consistent with a selective advantage. We do not find any indication that patients infected with the spike 614G variant have higher COVID-19 mortality or clinical severity, but 614G is associated with higher viral load and younger age of patients. Significant differences in growth and size of 614G phylogenetic clusters indicate a need for continued study of this variant

Stable DNA triple helix formation using oligonucleotides containing 2'-aminoethoxy,5-propargylamino-U

We have prepared oligonucleotides containing the novel base analogue 2'-aminoethoxy,5-proparaylamino-U in place of thymidine and examined their ability to form intermolecular and intramolecular triple helices by DNase I footprinting and thermal melting studies. The results were compared with those for oligonucleotides containing 5-propargylamino-dU and 2'-aminoethoxy-T. We find that the bis-substituted derivative produces a large increase in triplex stability, much greater than that produced by either of the monosubstituted analogues, which are roughly equipotent with each other. Intermolecular triplexes with 9-mer oligonucleotides containing three or four base modifications generate footprints at submicromolar concentrations even at pH 7.5, in contrast to the unmodified oligonucleotide, which failed to produce a footprint at pH 5.0, even at 30 muM. UV- and fluorescence melting studies with intramolecular triplexes confirmed that the bis-modified base produces a much greater increase in T-m than either modification alone

Measuring spirometry in a lung cancer screening cohort highlights possible underdiagnosis and misdiagnosis of COPD

Introduction COPD is underdiagnosed, and measurement of spirometry alongside low-dose computed tomography (LDCT) screening for lung cancer is one strategy to increase earlier diagnosis of this disease. Methods Ever-smokers at high risk of lung cancer were invited to the Yorkshire Lung Screening Trial for a lung health check (LHC) comprising LDCT screening, pre-bronchodilator spirometry and a smoking cessation service. In this cross-sectional study we present data on participant demographics, respiratory symptoms, lung function, emphysema on imaging and both self-reported and primary care diagnoses of COPD. Multivariable logistic regression analysis identified factors associated with possible underdiagnosis and misdiagnosis of COPD in this population, with airflow obstruction defined as forced expiratory volume in 1 s/forced vital capacity ratio <0.70. Results Out of 3920 LHC attendees undergoing spirometry, 17% had undiagnosed airflow obstruction with respiratory symptoms, representing potentially undiagnosed COPD. Compared to those with a primary care COPD code, this population had milder symptoms, better lung function and were more likely to be current smokers (p≤0.001 for all comparisons). Out of 836 attendees with a primary care COPD code who underwent spirometry, 19% did not have airflow obstruction, potentially representing misdiagnosed COPD, although symptom burden was high. Discussion Spirometry offered alongside LDCT screening can potentially identify cases of undiagnosed and misdiagnosed COPD. Future research should assess the downstream impact of these findings to determine whether any meaningful changes to treatment and outcomes occur, and to assess the impact on co-delivering spirometry on other parameters of LDCT screening performance such as participation and adherence. Additionally, work is needed to better understand the aetiology of respiratory symptoms in those with misdiagnosed COPD, to ensure that this highly symptomatic group receive evidence-based interventions

Participation in community-based lung cancer screening: the Yorkshire Lung Screening Trial

BACKGROUND: Screening with low-dose computed tomography (LDCT) reduces lung cancer mortality; however, the most effective strategy for optimising participation is unknown. Here we present data from the Yorkshire Lung Screening Trial, including response to invitation, screening eligibility and uptake of community-based LDCT screening. METHODS: Individuals aged 55–80 years, identified from primary care records as having ever smoked, were randomised prior to consent to invitation to telephone lung cancer risk assessment or usual care. The invitation strategy included general practitioner endorsement, pre-invitation and two reminder invitations. After telephone triage, those at higher risk were invited to a Lung Health Check (LHC) with immediate access to a mobile CT scanner. RESULTS: Of 44 943 individuals invited, 50.8% (n=22 815) responded and underwent telephone-based risk assessment (16.7% and 7.3% following first and second reminders, respectively). A lower response rate was associated with current smoking status (adjusted OR 0.44, 95% CI 0.42–0.46) and socioeconomic deprivation (adjusted OR 0.58, 95% CI 0.54–0.62 for the most versus the least deprived quintile). Of those responding, 34.4% (n=7853) were potentially eligible for screening and offered a LHC, of whom 86.8% (n=6819) attended. Lower uptake was associated with current smoking status (adjusted OR 0.73, 95% CI 0.62–0.87) and socioeconomic deprivation (adjusted OR 0.78, 95% CI 0.62–0.98). In total, 6650 individuals had a baseline LDCT scan, representing 99.7% of eligible LHC attendees. CONCLUSIONS: Telephone risk assessment followed by a community-based LHC is an effective strategy for lung cancer screening implementation. However, lower participation associated with current smoking status and socioeconomic deprivation underlines the importance of research to ensure equitable access to screening