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Biomedical subjects

Rachel Green

Publications and source records attributed to Rachel Green.

At least 19 recordsLinked to original sources
PubMed2026

Reported exposure to news portrayals about mental health problems and their impact: Findings from the 2025 National Survey of Stigma and Discrimination.

OBJECTIVE: Media portrayals of people with mental illness have the power to mitigate or perpetuate stigma related to mental health. This study aimed to investigate reported real-world exposure to news media portrayals about people with mental health problems in the past 12 months and the impact of these. METHODS: Data were from a nationally representative survey of 6032 Australians exploring attitudes towards people with mental health problems. Participants were asked about their exposure to positive news stories about a person with a mental health problem, as well as negative portrayals, in which someone was harmed by a person with a mental health problem. Further questions covered the sources (traditional or social media) and impact of these exposures. RESULTS: Regression models were used to explore sociodemographic predictors of impact. Most participants reported exposure to negative news portrayals (68.4%, 95% confidence interval = [66.9, 69.8]), while fewer reported exposure to positive news stories (33.7%, 95% confidence interval = [32.3, 35.2]). Most people exposed to the negative news stories reported a negative impact (69.0%, 95% confidence interval = [67.2, 70.7]), and most exposed to positive news stories reported a positive impact (80.2%, 95% confidence interval = [77.6, 82.5]). Age and gender were associated with reported impact but not lived experience of mental illness. CONCLUSIONS: Exposure to negative news stories about mental health problems was prevalent. Given their impact on news audiences broadly, negative news stories need to be accurate and responsible to mitigate negative impacts. A renewed focus on generating and promoting positive and stigma-challenging news stories is needed to increase subsequent positive impacts.

Humans↗
PubMed2006

Mutational analysis reveals two independent molecular requirements during transfer RNA selection on the ribosome.

Accurate discrimination between cognate and near-cognate aminoacyl-tRNAs during translation relies on the specific acceleration of forward rate constants for cognate tRNAs. Such specific rate enhancement correlates with conformational changes in the tRNA and small ribosomal subunit that depend on an RNA-specific type of interaction, the A-minor motif, between universally conserved 16S ribosomal RNA nucleotides and the cognate codon-anticodon helix. We show that perturbations of these two components of the A-minor motif, the conserved rRNA bases and the codon-anticodon helix, result in distinct outcomes. Although both cause decreases in the rates of tRNA selection that are rescued by aminoglycoside antibiotics, only disruption of the codon-anticodon helix is overcome by a miscoding tRNA variant. On this basis, we propose that two independent molecular requirements must be met to allow tRNAs to proceed through the selection pathway, providing a mechanism for exquisite control of fidelity during this step in gene expression.

Aminoglycosides↗
PubMed2006

A genomewide screen for components of the RNAi pathway in Drosophila cultured cells.

Posttranscriptional silencing by RNAi is initiated by dsRNAs that are processed into siRNAs that ultimately target homologous mRNAs for degradation. We used luciferase reporter constructs and a cultured cell-based assay to perform a genomewide screen for components of the RNAi pathway in Drosophila melanogaster. The screen identified seven genes that affect the RNAi response, five with previously described function (AGO2, Tis11, Hsc70-3, Hsc70-4, and hdc) and two annotated genes (CG17265 and CG10883).

Animals↗
PubMed2006

The hybrid state of tRNA binding is an authentic translation elongation intermediate.

The GTPase elongation factor (EF)-G is responsible for promoting the translocation of the messenger RNA-transfer RNA complex on the ribosome, thus opening up the A site for the next aminoacyl-tRNA. Chemical modification and cryo-EM studies have indicated that tRNAs can bind the ribosome in an alternative 'hybrid' state after peptidyl transfer and before translocation, though the relevance of this state during translation elongation has been a subject of debate. Here, using pre-steady-state kinetic approaches and mutant analysis, we show that translocation by EF-G is most efficient when tRNAs are bound in a hybrid state, supporting the argument that this state is an authentic intermediate during translation.

Escherichia coli↗
PubMed2006

The interaction between C75 of tRNA and the A loop of the ribosome stimulates peptidyl transferase activity.

Ribosomal variants carrying mutations in active site nucleotides are severely compromised in their ability to catalyze peptide bond formation (PT) with minimal aminoacyl tRNA substrates such as puromycin. However, catalysis of PT by these same ribosomes with intact aminoacyl tRNA substrates is uncompromised. These data suggest that these active site nucleotides play an important role in the positioning of minimal aminoacyl tRNA substrates but are not essential for catalysis per se when aminoacyl tRNAs are positioned by more remote interactions with the ribosome. Previously reported biochemical studies and atomic resolution X-ray structures identified a direct Watson-Crick interaction between C75 of the A-site substrate and G2553 of the 23S rRNA. Here we show that the addition of this single cytidine residue (the C75 equivalent) to puromycin is sufficient to suppress the deficiencies of active site ribosomal variants, thus restoring "tRNA-like" behavior to this minimal substrate. Studies of the binding parameters and the pH-dependence of catalysis with this minimal substrate indicate that the interaction between C75 and the ribosomal A loop is an essential feature for robust catalysis and further suggest that the observed effects of C75 on peptidyl transfer activity reflect previously reported conformational rearrangements in this active site.

Binding Sites↗
PubMed2006

Research papers submitted to Australian Family Physician - types and timelines.

BACKGROUND: Articles published in the research section of Australian Family Physician (AFP) are subject to an editorial process comprising several stages. METHOD: Timelines tracking the movement of each research manuscript submitted to AFP from 2002-2004 through all stages of the editorial process were constructed. Of 179 papers, 130 had sufficiently progressed to be included in this study. Manuscripts were grouped by subject matter into eight categories. RESULTS: Waiting for authors' responses to editorial feedback (with reviewers' reports) was the greatest cause of delay to AFP editorial processes. Peer reviewers took 43 (SD: 102) days to return their report. Authors took 67 (SD: 76) days to resubmit their paper following initial feedback, and a further 48 (SD: 79) days after it had been edited. Mean accumulated time between receipt of a manuscript by AFP and sending it to peer review was 15 days. Once the editorial process was completed, articles were usually published within 3 months. Most research (64%) was on the topic of health services research rather than clinical research (36%). The most common research method was observational (78%) rather than experimental (22%). DISCUSSION: There is less clinical research submitted to AFP than expected for a clinical discipline. Authors and reviewers cause the most delay in manuscripts' passage through the editorial process.

Australia↗
PubMed2006

The fate of papers rejected by Australian Family Physician.

BACKGROUND: Research papers submitted to Australian Family Physician (AFP) are accepted or rejected on the judgment of the research editor with advice from expert reviewers. Rejection can be outright (e.g., when research is "fatally flawed") or, more often, conditional (when authors are invited to respond to criticisms). Sometimes authors fail to resubmit. The fate of both groups of papers is unknown, as are the reasons for failing to resubmit. METHOD: We sent an explanatory email to all authors who submitted a paper to the AFP research section between 2002 and 2004, with a simple eight question survey (plus 1-2 additional questions for authors of rejected/withdrawn articles. RESULTS: Of 123 requests sent, 50 were returned (41% response rate). These were supplemented by an extra 19 papers identified by literature searching. Authors of accepted papers were more likely to participate than those whose papers were rejected or withdrawn. Most papers (28/47, 60%) submitted to AFP were written specifically for the journal. Those that were published underwent major change from the original submitted. Three out of 11 papers rejected by AFP were published in another journal. Authors who failed to resubmit (or withdrew) their paper usually cited being too busy. The editorial and peer review process was considered valuable by 74% of responders. Most accepted papers (20/37, 54%) underwent one revision; rejected articles were usually rejected outright (9/11, 82%). DISCUSSION: That authors often lose interest in getting their paper published after preparing it for submission is curious. Most authors consider peer and editorial review to be valuable.

Australia↗
PubMed2005

High affinity ligands for the alpha7 nicotinic receptor that show no cross-reactivity with the 5-HT3 receptor.

Potent and selective ligands of the alpha7 nicotinic acetylcholine receptor are required to understand the pharmacological effect of alpha7 activation. A common cross-reactivity occurs with serotonergic 5-HT3 receptors with which alpha7 receptors have a high sequence homology. We demonstrate that certain quinuclidine 3-biaryl carboxamides are high affinity alpha7 ligands with an excellent binding selectivity over 5-HT3 receptors.

Amides↗
PubMed2005

An active role for tRNA in decoding beyond codon:anticodon pairing.

During transfer RNA (tRNA) selection, a cognate codon:anticodon interaction triggers a series of events that ultimately results in the acceptance of that tRNA into the ribosome for peptide-bond formation. High-fidelity discrimination between the cognate tRNA and near- and noncognate ones depends both on their differential dissociation rates from the ribosome and on specific acceleration of forward rate constants by cognate species. Here we show that a mutant tRNA(Trp) carrying a single substitution in its D-arm achieves elevated levels of miscoding by accelerating these forward rate constants independent of codon:anticodon pairing in the decoding center. These data provide evidence for a direct role for tRNA in signaling its own acceptance during decoding and support its fundamental role during the evolution of protein synthesis.

Anticodon↗
PubMed2005

Multiple effects of S13 in modulating the strength of intersubunit interactions in the ribosome during translation.

The ribosomal protein S13 is found in the head region of the small subunit, where it interacts with the central protuberance of the large ribosomal subunit and with the P site-bound tRNA through its extended C terminus. The bridging interactions between the large and small subunits are dynamic, and are thought to be critical in orchestrating the molecular motions of the translation cycle. S13 provides a direct link between the tRNA-binding site and the movements in the head of the small subunit seen during translocation, thereby providing a possible pathway of signal transduction. We have created and characterized an rpsM(S13)-deficient strain of Escherichia coli and have found significant defects in subunit association, initiation and translocation through in vitro assays of S13-deficient ribosomes. Targeted mutagenesis of specific bridge and tRNA contact elements in S13 provides evidence that these two interaction domains play critical roles in maintaining the fidelity of translation. This ribosomal protein thus appears to play a non-essential, yet important role by modulating subunit interactions in multiple steps of the translation cycle.

Biological Assay↗
PubMed2005

Affinity purification of in vivo-assembled ribosomes for in vitro biochemical analysis.

As it has become increasingly clear that the RNA components of the ribosome are central to its function, the in vitro analysis of mutations in the ribosomal RNAs has become an important tool for understanding the molecular details of ribosome function. However, the frequent dominant lethal phenotypes of mutations at interesting rRNA residues has long presented a hurdle to this analysis, as their lethality has rendered it impossible to generate pure populations of in vivo-derived ribosomes for study. We present here the details of a method for affinity purification of ribosomes bearing any mutation in the 16S or 23S rRNA and demonstrate that ribosomes purified using this technology are highly active in the several steps of translation we have examined.

Base Sequence↗
PubMed2004

RNA chaperone activity of large ribosomal subunit proteins from Escherichia coli.

The ribosome is a highly dynamic ribonucleoprotein machine. During assembly and during translation the ribosomal RNAs must routinely be prevented from falling into kinetic folding traps. Stable occupation of these trapped states may be prevented by proteins with RNA chaperone activity. Here, ribosomal proteins from the large (50S) ribosome subunit of Escherichia coli were tested for RNA chaperone activity in an in vitro trans splicing assay. Nearly a third of the 34 large ribosomal subunit proteins displayed RNA chaperone activity. We discuss a possible role of this function during ribosome assembly and during translation.

Escherichia coli↗
PubMed2004

Substrate-assisted catalysis of peptide bond formation by the ribosome.

The ribosome accelerates the rate of peptide bond formation by at least 10(7)-fold, but the catalytic mechanism remains controversial. Here we report evidence that a functional group on one of the tRNA substrates plays an essential catalytic role in the reaction. Substitution of the P-site tRNA A76 2' OH with 2' H or 2' F results in at least a 10(6)-fold reduction in the rate of peptide bond formation, but does not affect binding of the modified substrates. Such substrate-assisted catalysis is relatively uncommon among modern protein enzymes, but it is a property predicted to be essential for the evolution of enzymatic function. These results suggest that substrate assistance has been retained as a catalytic strategy during the evolution of the prebiotic peptidyl transferase center into the modern ribosome.

Base Sequence↗
PubMed2004

The active site of the ribosome is composed of two layers of conserved nucleotides with distinct roles in peptide bond formation and peptide release.

Peptide bond formation and peptide release are catalyzed in the active site of the large subunit of the ribosome where universally conserved nucleotides surround the CCA ends of the peptidyl- and aminoacyl-tRNA substrates. Here, we describe the use of an affinity-tagging system for the purification of mutant ribosomes and analysis of four universally conserved nucleotides in the innermost layer of the active site: A2451, U2506, U2585, and A2602. While pre-steady-state kinetic analysis of the peptidyl transferase activity of the mutant ribosomes reveals substantially reduced rates of peptide bond formation using the minimal substrate puromycin, their rates of peptide bond formation are unaffected when the substrates are intact aminoacyl-tRNAs. These mutant ribosomes do, however, display substantial defects in peptide release. These results reveal a view of the catalytic center in which an inner shell of conserved nucleotides is pivotal for peptide release, while an outer shell is responsible for promoting peptide bond formation.

Base Sequence↗
PubMed2004

Isolation of antibiotic resistance mutations in the rRNA by using an in vitro selection system.

Genetic, biochemical, and structural data support an essential role for the ribosomal RNA in all steps of the translation process. Although in vivo genetic selection techniques have been used to identify mutations in the rRNAs that result in various miscoding phenotypes and resistance to known ribosome-targeted antibiotics, these are limited because the resulting mutant ribosomes must be only marginally disabled if they are able to support growth of the cell. Furthermore, in vivo, it is not possible to control the environment in precise ways that might allow for the isolation of certain types of rRNA variants. To overcome these limitations, we have developed an in vitro selection system for the isolation of functionally competent ribosomal particles from populations containing variant rRNAs. Here, we describe this system and present an example of its application to the selection of antibiotic resistance mutations. From a pool of 4,096 23S rRNA variants, a double mutant (A2058U/A2062G) was isolated after iteration of the selection process. This mutant was highly resistant to clindamycin in in vitro translation reactions and yet was not viable in Escherichia coli. These data establish that this system has the potential to identify mutations in the rRNA not readily accessed by comparable in vivo systems, thus allowing for more exhaustive ribosomal genetic screens.

Clindamycin↗