66,016 research outputs found
Fluorescent protein tagging confirms the presence of ribosomal proteins atDrosophilapolytene chromosomes
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Most ribosomal proteins (RPs) are stoichiometrically incorporated into ribosomal subunits and play essential roles in ribosome biogenesis and function. However, a number of RPs appear to have non-ribosomal functions, which involve direct association with pre-mRNA and transcription factors at transcription sites. The consensus is that the RPs found at these sites are off ribosomal subunits, but observation that different RPs are usually found together suggests that ribosomal or ribosomal-like subunits might be present. Notably, it has previously been reported that antibodies against 20 different RPs stain the same Pol II transcription sites in Drosophila polytene chromosomes. Some concerns, however, were raised about the specificity of the antibodies. To investigate further whether RPs are present at transcription sites in Drosophila, we have generated several transgenic flies expressing RPs (RpS2, RpS5a, RpS9, RpS11, RpS13, RpS18, RpL8, RpL11, RpL32, and RpL36) tagged with either green or red fluorescent protein. Imaging of salivary gland cells showed that these proteins are, as expected, abundant in the cytoplasm as well as in the nucleolus. However, these RPs are also apparent in the nucleus in the region occupied by the chromosomes. Indeed, polytene chromosome immunostaining of a representative subset of tagged RPs confirms the association with transcribed loci. Furthermore, characterization of a strain expressing RpL41 functionally tagged at its native genomic locus with YFP, also showed apparent nuclear accumulation and chromosomal association, suggesting that such a nuclear localization pattern might be a shared feature of RPs and is biologically important. We anticipate that the transgenes described here should provide a useful research tool to visualize ribosomal subunits in Drosophila tissues and to study the non-ribosomal functions of RPs.\u
Survival of Massive Star-forming Galaxies in Cluster Cores Drives Gas-Phase Metallicity Gradients : The Effects of Ram Pressure Stripping
Recent observations of galaxies in a cluster at z=0.35 show that their
integrated gas-phase metallicities increase with decreasing cluster-centric
distance. To test if ram pressure stripping (RPS) is the underlying cause, we
use a semi-analytic model to quantify the "observational bias" that RPS
introduces into the aperture-based metallicity measurements. We take integral
field spectroscopy of local galaxies, remove gas from their outer galactic
disks via RPS, and then conduct mock slit observations of cluster galaxies at
z=0.35. Our RPS model predicts a typical cluster-scale metallicity gradient of
-0.03 dex/Mpc. By removing gas from the outer galactic disks, RPS introduces a
mean metallicity enhancement of +0.02 dex at a fixed stellar mass. This gas
removal and subsequent quenching of star formation preferentially removes low
mass cluster galaxies from the observed star-forming population. As only the
more massive star-forming galaxies survive to reach the cluster core, RPS
produces a cluster-scale stellar mass gradient of -0.05 log(M_*/M_sun)/Mpc.
This mass segregation drives the predicted cluster-scale metallicity gradient
of -0.03 dex/Mpc. However, the effects of RPS alone can not explain the higher
metallicities measured in cluster galaxies at z=0.35. We hypothesize that
additional mechanisms including steep internal metallicity gradients and
self-enrichment due to gas strangulation are needed to reproduce our
observations at z=0.35.Comment: 17 pages, 21 figures, accepted for publication Ap
An HPSG approach to Welsh unbounded dependencies
Welsh is a language in which unbounded dependency constructions involve both gaps and resumptive pronouns (RPs). Gaps and RPs appear in disjoint sets of environments. Otherwise, however, they are quite similar. This suggests that they involve the same mechanism, and in HPSG that they involve the SLASH feature. It is possible to provide an analysis in which RPs are associated with the SLASH feature but are also the ordinary pronouns which they appear to be
Brain Trust: Students for Students: VCU to RPS Mentorship Program
As a public, urban research institution, Virginia Commonwealth University embraces the importance of developing university-community partnerships that generate innovative solutions to societal challenges and prepare engaged citizens of tomorrow. The Students for Students: VCU to RPS Mentorship Program provides a model that will connect current VCU students to current Richmond Public Schools (RPS) students through a formal, multi-year mentorship. The ultimate goal of this program is to support and positively influence RPS students, while providing current VCU students with an opportunity to give back to the community while developing their mentorship skills. The mentoring relationship will seek to motivate RPS sophomores, juniors and seniors to improve school performance, graduate on time, and craft a post-high school path
Differential stoichiometry among core ribosomal proteins
Understanding the regulation and structure of ribosomes is essential to
understanding protein synthesis and its deregulation in disease. While
ribosomes are believed to have a fixed stoichiometry among their core ribosomal
proteins (RPs), some experiments suggest a more variable composition. Testing
such variability requires direct and precise quantification of RPs. We used
mass-spectrometry to directly quantify RPs across monosomes and polysomes of
mouse embryonic stem cells (ESC) and budding yeast. Our data show that the
stoichiometry among core RPs in wild-type yeast cells and ESC depends both on
the growth conditions and on the number of ribosomes bound per mRNA.
Furthermore, we find that the fitness of cells with a deleted RP-gene is
inversely proportional to the enrichment of the corresponding RP in polysomes.
Together, our findings support the existence of ribosomes with distinct protein
composition and physiological function.Comment: 31 pages, 8 figure
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