Predicting translational progress in biomedical research.

Fundamental scientific advances can take decades to translate into improvements in human health. Shortening this interval would increase the rate at which scientific discoveries lead to successful treatment of human disease. One way to accomplish this would be to identify which advances in knowledge are most likely to translate into clinical research. Toward that end, we built a machine learning system that detects whether a paper is likely to be cited by a future clinical trial or guideline. Despite the noisiness of citation dynamics, as little as 2 years of postpublication data yield accurate predictions about a paper's eventual citation by a clinical article (accuracy = 84%, F1 score = 0.56; compared to 19% accuracy by chance). We found that distinct knowledge flow trajectories are linked to papers that either succeed or fail to influence clinical research. Translational progress in biomedicine can therefore be assessed and predicted in real time based on information conveyed by the scientific community's early reaction to a paper.

The NIH Open Citation Collection: A public access, broad coverage resource.

Citation data have remained hidden behind proprietary, restrictive licensing agreements, which raises barriers to entry for analysts wishing to use the data, increases the expense of performing large-scale analyses, and reduces the robustness and reproducibility of the conclusions. For the past several years, the National Institutes of Health (NIH) Office of Portfolio Analysis (OPA) has been aggregating and enhancing citation data that can be shared publicly. Here, we describe the NIH Open Citation Collection (NIH-OCC), a public access database for biomedical research that is made freely available to the community. This dataset, which has been carefully generated from unrestricted data sources such as MedLine, PubMed Central (PMC), and CrossRef, now underlies the citation statistics delivered in the NIH iCite analytic platform. We have also included data from a machine learning pipeline that identifies, extracts, resolves, and disambiguates references from full-text articles available on the internet. Open citation links are available to the public in a major update of iCite (https://icite.od.nih.gov).

Relative Citation Ratio (RCR): A New Metric That Uses Citation Rates to Measure Influence at the Article Level.

Despite their recognized limitations, bibliometric assessments of scientific productivity have been widely adopted. We describe here an improved method to quantify the influence of a research article by making novel use of its co-citation network to field-normalize the number of citations it has received. Article citation rates are divided by an expected citation rate that is derived from performance of articles in the same field and benchmarked to a peer comparison group. The resulting Relative Citation Ratio is article level and field independent and provides an alternative to the invalid practice of using journal impact factors to identify influential papers. To illustrate one application of our method, we analyzed 88,835 articles published between 2003 and 2010 and found that the National Institutes of Health awardees who authored those papers occupy relatively stable positions of influence across all disciplines. We demonstrate that the values generated by this method strongly correlate with the opinions of subject matter experts in biomedical research and suggest that the same approach should be generally applicable to articles published in all areas of science. A beta version of iCite, our web tool for calculating Relative Citation Ratios of articles listed in PubMed, is available at https://icite.od.nih.gov.

National Institutes of Health Funding for Surgeon-Scientists in the US-An Update and an Expanded Landscape.

Importance: Current reports suggest that the surgeon-scientist phenotype is significantly threatened. However, a significant increase in the proportion of surgeons in the workforce funded by the National Institutes of Health (NIH) from 2010 (0.5%) to 2020 (0.7%) was recently reported and showed that surgeons primarily performed basic science research (78% in 2010; 73% in 2020) rather than clinical research. Objective: To provide an update on the status of surgeons funded by the NIH for fiscal year (FY) 2022. Evidence Review: NIH-funded surgeons were identified in FY2012 and FY2022, including those who were awarded grants with more than 1 principal investigator (PI) by querying the internal database at the NIH. The main outcome for this study was the total number of NIH-funded surgeons in FY2012 and FY2022, including total grant costs and number of grants. The secondary analysis included self-reported demographic characteristics of the surgeons in FY2022. The research type (basic science vs clinical) of R01 grants was also examined. Findings: Including multiple PI grants, 1324 surgeon-scientists were awarded $1.3 billion in FY2022. Women surgeons increased to 31.3% (339 of 1084) of the population of surgeon PIs in FY2022 compared with 21.0% (184 of 876) in FY2012. Among surgeon PIs awarded grants, a total of 200 (22.8%) were Asian, 35 (4.0%) were Black or African American, 18 (2.1%) were another race (including American Indian or Alaska Native, Native Hawaiian or Other Pacific Islander, and more than 1 race), and 623 (71.1%) were White. A total of 513 of 689 R01 grants (74.5%) were for basic science, 131 (19.0%) were for clinical trials, and 45 (6.5%) were for outcomes research. Conclusions and Relevance: NIH-funded surgeons are increasing in number and grant costs, including the proportion of women surgeon PIs, and are representative of the diversity among US academic surgical faculty. The results of this study suggest that despite the many obstacles surgeon-scientists face, their research portfolio continues to grow, they perform a myriad of mostly basic scientific research as both independent PIs and on multidisciplinary teams.

Glucose signaling in Saccharomyces cerevisiae.

Eukaryotic cells possess an exquisitely interwoven and fine-tuned series of signal transduction mechanisms with which to sense and respond to the ubiquitous fermentable carbon source glucose. The budding yeast Saccharomyces cerevisiae has proven to be a fertile model system with which to identify glucose signaling factors, determine the relevant functional and physical interrelationships, and characterize the corresponding metabolic, transcriptomic, and proteomic readouts. The early events in glucose signaling appear to require both extracellular sensing by transmembrane proteins and intracellular sensing by G proteins. Intermediate steps involve cAMP-dependent stimulation of protein kinase A (PKA) as well as one or more redundant PKA-independent pathways. The final steps are mediated by a relatively small collection of transcriptional regulators that collaborate closely to maximize the cellular rates of energy generation and growth. Understanding the nuclear events in this process may necessitate the further elaboration of a new model for eukaryotic gene regulation, called "reverse recruitment." An essential feature of this idea is that fine-structure mapping of nuclear architecture will be required to understand the reception of regulatory signals that emanate from the plasma membrane and cytoplasm. Completion of this task should result in a much improved understanding of eukaryotic growth, differentiation, and carcinogenesis.

Chemical inhibition of CaaX protease activity disrupts yeast Ras localization.

Proteins possessing a C-terminal CaaX motif, such as the Ras GTPases, undergo extensive post-translational modification that includes attachment of an isoprenoid lipid, proteolytic processing and carboxylmethylation. Inhibition of the enzymes involved in these processes is considered a cancer-therapeutic strategy. We previously identified nine in vitro inhibitors of the yeast CaaX protease Rce1p in a chemical library screen (Manandhar et al., 2007). Here, we demonstrate that these agents disrupt the normal plasma membrane distribution of yeast GFP-Ras reporters in a manner that pharmacologically phenocopies effects observed upon genetic loss of CaaX protease function. Consistent with Rce1p being the in vivo target of the inhibitors, we observe that compound-induced delocalization is suppressed by increasing the gene dosage of RCE1. Moreover, we observe that Rce1p biochemical activity associated with inhibitor-treated cells is inversely correlated with compound dose. Genetic loss of CaaX proteolysis results in mistargeting of GFP-Ras2p to subcellular foci that are positive for the endoplasmic reticulum marker Sec63p. Pharmacological inhibition of CaaX protease activity also delocalizes GFP-Ras2p to foci, but these foci are not as strongly positive for Sec63p. Lastly, we demonstrate that heterologously expressed human Rce1p can mediate proper targeting of yeast Ras and that its activity can also be perturbed by some of the above inhibitors. Together, these results indicate that disrupting the proteolytic modification of Ras GTPases impacts their in vivo trafficking.

Heterologous expression studies of Saccharomyces cerevisiae reveal two distinct trypanosomatid CaaX protease activities and identify their potential targets.

The CaaX tetrapeptide motif typically directs three sequential posttranslational modifications, namely, isoprenylation, proteolysis, and carboxyl methylation. In all eukaryotic systems evaluated to date, two CaaX proteases (Rce1 and Ste24/Afc1) have been identified. Although the Trypanosoma brucei genome also encodes two putative CaaX proteases, the lack of detectable T. brucei Ste24 activity in trypanosome cell extracts has suggested that CaaX proteolytic activity within this organism is solely attributed to T. brucei Rce1 (J. R. Gillespie et al., Mol. Biochem. Parasitol. 153:115-124. 2007). In this study, we demonstrate that both T. brucei Rce1 and T. brucei Ste24 are enzymatically active when heterologously expressed in yeast. Using a-factor and GTPase reporters, we demonstrate that T. brucei Rce1 and T. brucei Ste24 possess partially overlapping specificities much like, but not identical to, their fungal and human counterparts. Of interest, a CaaX motif found on a trypanosomal Hsp40 protein was not cleaved by either T. brucei CaaX protease when examined in the context of the yeast a-factor reporter but was cleaved by both in the context of the Hsp40 protein itself when evaluated using an in vitro radiolabeling assay. We further demonstrate that T. brucei Rce1 is sensitive to small molecules previously identified as inhibitors of the yeast and human CaaX proteases and that a subset of these compounds disrupt T. brucei Rce1-dependent localization of our GTPase reporter in yeast. Together, our results suggest the conserved presence of two CaaX proteases in trypanosomatids, identify an Hsp40 protein as a substrate of both T. brucei CaaX proteases, support the potential use of small molecule CaaX protease inhibitors as tools for cell biological studies on the trafficking of CaaX proteins, and provide evidence that protein context influences T. brucei CaaX protease specificity.

Topic choice contributes to the lower rate of NIH awards to African-American/black scientists.

Despite efforts to promote diversity in the biomedical workforce, there remains a lower rate of funding of National Institutes of Health R01 applications submitted by African-American/black (AA/B) scientists relative to white scientists. To identify underlying causes of this funding gap, we analyzed six stages of the application process from 2011 to 2015 and found that disparate outcomes arise at three of the six: decision to discuss, impact score assignment, and a previously unstudied stage, topic choice. Notably, AA/B applicants tend to propose research on topics with lower award rates. These topics include research at the community and population level, as opposed to more fundamental and mechanistic investigations; the latter tend to have higher award rates. Topic choice alone accounts for over 20% of the funding gap after controlling for multiple variables, including the applicant's prior achievements. Our findings can be used to inform interventions designed to close the funding gap.

Glucose-responsive regulators of gene expression in Saccharomyces cerevisiae function at the nuclear periphery via a reverse recruitment mechanism.

Regulation of gene transcription is a key feature of developmental, homeostatic, and oncogenic processes. The reverse recruitment model of transcriptional control postulates that eukaryotic genes become active by moving to contact transcription factories at nuclear substructures; our previous work showed that at least some of these factories are tethered to nuclear pores. We demonstrate here that the nuclear periphery is the site of key events in the regulation of glucose-repressed genes, which together compose one-sixth of the Saccharomyces cerevisiae genome. We also show that the canonical glucose-repressed gene SUC2 associates tightly with the nuclear periphery when transcriptionally active but is highly mobile when repressed. Strikingly, SUC2 is both derepressed and confined to the nuclear rim in mutant cells where the Mig1 repressor is nuclear but not perinuclear. Upon derepression all three subunits (alpha, beta, and gamma) of the positively acting Snf1 kinase complex localize to the nuclear periphery, resulting in phosphorylation of Mig1 and its export to the cytoplasm. Reverse recruitment therefore appears to explain a fundamental pathway of eukaryotic gene regulation.

Article-level assessment of influence and translation in biomedical research.

Given the vast scale of the modern scientific enterprise, it can be difficult for scientists to make judgments about the work of others through careful analysis of the entirety of the relevant literature. This has led to a reliance on metrics that are mathematically flawed and insufficiently diverse to account for the variety of ways in which investigators contribute to scientific progress. An urgent, critical first step in solving this problem is replacing the Journal Impact Factor with an article-level alternative. The Relative Citation Ratio (RCR), a metric that was designed to serve in that capacity, measures the influence of each publication on its respective area of research. RCR can serve as one component of a multifaceted metric that provides an effective data-driven supplement to expert opinion. Developing validated methods that quantify scientific progress can help to optimize the management of research investments and accelerate the acquisition of knowledge that improves human health.

The global transcriptional activator of Saccharomyces cerevisiae, Gcr1p, mediates the response to glucose by stimulating protein synthesis and CLN-dependent cell cycle progression.

Growth of Saccharomyces cerevisiae requires coordination of cell cycle events (e.g., new cell wall deposition) with constitutive functions like energy generation and duplication of protein mass. The latter processes are stimulated by the phosphoprotein Gcr1p, a transcriptional activator that operates through two different Rap1p-mediated mechanisms to boost expression of glycolytic and ribosomal protein genes, respectively. Simultaneous disruption of both mechanisms results in a loss of glucose responsiveness and a dramatic drop in translation rate. Since a critical rate of protein synthesis (CRPS) is known to mediate passage through Start and determine cell size by modulating levels of Cln3p, we hypothesized that GCR1 regulates cell cycle progression by coordinating it with growth. We therefore constructed and analyzed gcr1delta cln3delta and gcr1delta cln1delta cln2delta strains. Both strains are temperature and cold sensitive; interestingly, they exhibit different arrest phenotypes. The gcr1delta cln3delta strain becomes predominantly unbudded with 1N DNA content (G1 arrest), whereas gcr1delta cln1delta cln2delta cells exhibit severe elongation and apparent M phase arrest. Further analysis demonstrated that the Rap1p/Gcr1p complex mediates rapid growth in glucose by stimulating both cellular metabolism and CLN transcription.

The nuclear pore complex mediates binding of the Mig1 repressor to target promoters.

All eukaryotic cells alter their transcriptional program in response to the sugar glucose. In Saccharomyces cerevisiae, the best-studied downstream effector of this response is the glucose-regulated repressor Mig1. We show here that nuclear pore complexes also contribute to glucose-regulated gene expression. NPCs participate in glucose-responsive repression by physically interacting with Mig1 and mediating its function independently of nucleocytoplasmic transport. Surprisingly, despite its abundant presence in the nucleus of glucose-grown nup120Δ or nup133Δ cells, Mig1 has lost its ability to interact with target promoters. The glucose repression defect in the absence of these nuclear pore components therefore appears to result from the failure of Mig1 to access its consensus recognition sites in genomic DNA. We propose that the NPC contributes to both repression and activation at the level of transcription.

Coiled coil structures and transcription: an analysis of the S. cerevisiae coilome.

The alpha-helical coiled coil is a simple but widespread motif that is an integral feature of many cellular structures. Coiled coils allow monomeric building blocks to form complex assemblages that can serve as molecular motors and springs. Previous parametrically delimited analyses of the distribution of coiled coils in the genomes of diverse organisms, including Escherichia coli, Saccharomyces cerevisiae, Arabidopsis thaliana, Caenorhabditis elegans and Homo sapiens, have identified conserved biological processes that make use of this versatile motif. Here we present a comprehensive inventory of the set of coiled coil proteins in S. cerevisiae by combining multiple coiled coil prediction algorithms with extensive literature curation. Our analysis of this set of proteins, which we call the coilome, reveals a wider role for this motif in transcription than was anticipated, particularly with respect to the category that includes nucleocytoplasmic shuttling factors involved in transcriptional regulation. We also show that the constitutively nuclear yeast transcription factor Gcr1 is homologous to the mammalian transcription factor MLL3, and that two coiled coil domains conserved between these homologs are important for Gcr1 dimerization and function. These data support the hypothesis that coiled coils are required to assemble structures essential for proper functioning of the transcriptional machinery.

The transcription factor Gcr1 stimulates cell growth by participating in nutrient-responsive gene expression on a global level.

Transcriptomic reprogramming is critical to the coordination between growth and cell cycle progression in response to changing extracellular conditions. In Saccharomyces cerevisiae, the transcription factor Gcr1 contributes to this coordination by supporting maximum expression of G1 cyclins in addition to regulating both glucose-induced and glucose-repressed genes. We report here the comprehensive genome-wide expression profiling of gcr1Delta cells. Our data show that reduced expression of ribosomal protein genes in gcr1Delta cells is detectable both 20 min after glucose addition and in steady-state cultures of raffinose-grown cells, showing that this defect is not the result of slow growth or growth on a repressing sugar. However, the large cell phenotype of the gcr1Delta mutant occurs only in the presence of repressing sugars. GCR1 deletion also results in aberrant derepression of numerous glucose repressed loci; glucose-grown gcr1Delta cells actively respire, demonstrating that this global alteration in transcription corresponds to significant changes at the physiological level. These data offer an insight into the coordination of growth and cell division by providing an integrated view of the transcriptomic, phenotypic, and metabolic consequences of GCR1 deletion.

Reverse recruitment: the Nup84 nuclear pore subcomplex mediates Rap1/Gcr1/Gcr2 transcriptional activation.

The recruitment model for gene activation presumes that DNA is a platform on which the requisite components of the transcriptional machinery are assembled. In contrast to this idea, we show here that Rap1/Gcr1/Gcr2 transcriptional activation in yeast cells occurs through a large anchored protein platform, the Nup84 nuclear pore subcomplex. Surprisingly, Nup84 and associated subcomplex components activate transcription themselves in vivo when fused to a heterologous DNA-binding domain. The Rap1 coactivators Gcr1 and Gcr2 form an important bridge between the yeast nuclear pore complex and the transcriptional machinery. Nucleoporin activation may be a widespread eukaryotic phenomenon, because it was first detected as a consequence of oncogenic rearrangements in acute myeloid leukemia and related syndromes in humans. These chromosomal translocations fuse a homeobox DNA-binding domain to the human homolog (hNup98) of a transcriptionally active component of the yeast Nup84 subcomplex. We conclude that Rap1 target genes are activated by moving to contact compartmentalized nuclear assemblages, rather than through recruitment of the requisite factors to chromatin by means of diffusion. We term this previously undescribed mechanism "reverse recruitment" and discuss the possibility that it is a central feature of eukaryotic gene regulation. Reverse recruitment stipulates that activators work by bringing the DNA to an nuclear pore complex-tethered platform of assembled transcriptional machine components.