Blanks, a nuclear siRNA/dsRNA-binding complex component, is required for Drosophila spermiogenesis

Small RNAs and a diverse array of protein partners control gene expression in eukaryotes through a variety of mechanisms. By combining siRNA affinity chromatography and mass spectrometry, we have identified the double-stranded RNA-binding domain protein Blanks to be an siRNA- and dsRNA-binding protein from Drosophila S2 cells. We find that Blanks is a nuclear factor that contributes to the efficiency of RNAi. Biochemical fractionation of a Blanks-containing complex shows that the Blanks complex is unlike previously described RNA-induced silencing complexes and associates with the DEAD-box helicase RM62, a protein previously implicated in RNA silencing. In flies, Blanks is highly expressed in testes tissues and is necessary for postmeiotic spermiogenesis, but loss of Blanks is not accompanied by detectable transposon derepression. Instead, genes related to innate immunity pathways are up-regulated in blanks mutant testes. These results reveal Blanks to be a unique component of a nuclear siRNA/dsRNA-binding complex that contributes to essential RNA silencing-related pathways in the male germ line

The Lyman Continuum escape fraction of galaxies at z=3.3 in the VUDS-LBC/COSMOS field

The Lyman continuum (LyC) flux escaping from high-z galaxies into the IGM is a fundamental quantity to understand the physical processes involved in the reionization epoch. We have investigated a sample of star-forming galaxies at z~3.3 in order to search for possible detections of LyC photons escaping from galaxy halos. UV deep imaging in the COSMOS field obtained with the prime focus camera LBC at the LBT telescope was used together with a catalog of spectroscopic redshifts obtained by the VIMOS Ultra Deep Survey (VUDS) to build a sample of 45 galaxies at z~3.3 with L>0.5L*. We obtained deep LBC images of galaxies with spectroscopic redshifts in the interval 3.27<z<3.40 both in the R and deep U bands. A sub-sample of 10 galaxies apparently shows escape fractions>28% but a detailed analysis of their properties reveals that, with the exception of two marginal detections (S/N~2) in the U band, all the other 8 galaxies are most likely contaminated by the UV flux of low-z interlopers located close to the high-z targets. The average escape fraction derived from the stacking of the cleaned sample was constrained to fesc_rel<2%. The implied HI photo-ionization rate is a factor two lower than that needed to keep the IGM ionized at z~3, as observed in the Lyman forest of high-z QSO spectra or by the proximity effect. These results support a scenario where high redshift, relatively bright (L>0.5L*) star-forming galaxies alone are unable to sustain the level of ionization observed in the cosmic IGM at z~3. Star-forming galaxies at higher redshift and at fainter luminosities (L<<L*) can be the major contributors to the reionization of the Universe only if their physical properties are subject to rapid changes from z~3 to z~6-10. Alternatively, ionizing sources could be discovered looking for fainter sources among the AGN population at high-z.Comment: 21 pages, 9 figures. Accepted for publication in A&

Mental health training for secondary school teachers in Haiti: a mixed methods, prospective, formative research study of feasibility, acceptability, and effectiveness in knowledge acquisition

Background: Engagement and training of educators in student mental health holds promise for promoting access to care as a task sharing strategy but has not been well-studied in low-income regions. Methods: We used a prospective and convergent mixed methods design to evaluate a customized school mental health 2½ day training for teachers in rural Haiti (n = 22) as the initial component of formative research developing a school-based intervention to promote student mental health. Training prepared teachers to respond to student mental health needs by providing psychoeducational and practical support to facilitate access to care. We examined level of participation and evaluated feasibility, acceptability, and perceived effectiveness by calculating mean scores on self-report Likert-style items eliciting participant experience. We examined effectiveness of the training on improving mental health knowledge and attitudes by comparing mean scores on an assessment administered pre- and post-training. Finally, we examined self-report written open-ended responses and focus group discussion (FGD) interview data bearing on perceived feasibility, acceptability, and effectiveness to contextualize participant ratings of training and to identify recommendations for enhancing the utility of mental health training locally for educators. Results: Mean scores of knowledge and attitudes significantly improved between the pre-test and post-tests; e.g., knowledge improved from 58% correct at baseline to 68% correct on the second post-test (p = 0.039). Mean ratings of the training were favorable across all categories and FGD data demonstrated widespread participant endorsement of training acceptability and effectiveness; participants recommended extending the duration and number of training sessions. Conclusions: Findings support feasibility, acceptability, and a limited scope of effectiveness of brief mental health training for secondary school teachers in Haiti. Further development of approaches to engage teachers in promoting school mental health through training is warranted

Rational Extension of the Ribosome Biogenesis Pathway Using Network-Guided Genetics

Gene networks are an efficient route for associating candidate genes with biological processes. Here, networks are used to discover more than 15 new genes for ribosomal subunit maturation, rRNA processing, and ribosomal export from the nucleus

Trypanosomatid RACK1 Orthologs Show Functional Differences Associated with Translation Despite Similar Roles in Leishmania Pathogenesis

RACK1 proteins belong to the eukaryote WD40-repeat protein family and function as spatial regulators of multiple cellular events, including signaling pathways, the cell cycle and translation. For this latter role, structural and genetic studies indicate that RACK1 associates with the ribosome through two conserved positively charged amino acids in its first WD40 domain. Unlike RACK1s, including Trypanosoma brucei RACK1 (TbRACK1), only one of these two positively-charged residues is conserved in the first WD40 domain of the Leishmania major RACK1 ortholog, LACK. We compared virulence-attenuated LACK single copy (LACK/-) L. major, with L. major expressing either two LACK copies (LACK/LACK), or one copy each of LACK and TbRACK1 (LACK/TbRACK1), to evaluate the function of these structurally distinct RACK1 orthologs with respect to translation, viability at host temperatures and pathogenesis. Our results indicate that although the ribosome-binding residues are not fully conserved in LACK, both LACK and TbRACK1 co-sedimented with monosomes and polysomes in LACK/LACK and LACK/TbRACK1 L. major, respectively. LACK/LACK and LACK/TbRACK1 strains differed in their sensitivity to translation inhibitors implying that minor sequence differences between the RACK1 proteins can alter their functional properties. While biochemically distinguishable, both LACK/LACK and LACK/TbRACK1 lines were more tolerant of elevated temperatures, resistant to translation inhibitors, and displayed robust pathogenesis in vivo, contrasting to LACK/- parasites

Yeast Asc1p and Mammalian RACK1 Are Functionally Orthologous Core 40S Ribosomal Proteins That Repress Gene Expression

Translation of mRNA into protein is a fundamental step in eukaryotic gene expression requiring the large (60S) and small (40S) ribosome subunits and associated proteins. By modern proteomic approaches, we previously identified a novel 40S-associated protein named Asc1p in budding yeast and RACK1 in mammals. The goals of this study were to establish Asc1p or RACK1 as a core conserved eukaryotic ribosomal protein and to determine the role of Asc1p or RACK1 in translational control. We provide biochemical, evolutionary, genetic, and functional evidence showing that Asc1p or RACK1 is indeed a conserved core component of the eukaryotic ribosome. We also show that purified Asc1p-deficient ribosomes have increased translational activity compared to that of wild-type yeast ribosomes. Further, we demonstrate that asc1Δ null strains have increased levels of specific proteins in vivo and that this molecular phenotype is complemented by either Asc1p or RACK1. Our data suggest that one of Asc1p's or RACK1's functions is to repress gene expression