The dynamic architecture of Map1- and NatB-ribosome complexes coordinates the sequential modifications of nascent polypeptide chains.

Cotranslational modification of the nascent polypeptide chain is one of the first events during the birth of a new protein. In eukaryotes, methionine aminopeptidases (MetAPs) cleave off the starter methionine, whereas N-acetyl-transferases (NATs) catalyze N-terminal acetylation. MetAPs and NATs compete with other cotranslationally acting chaperones, such as ribosome-associated complex (RAC), protein targeting and translocation factors (SRP and Sec61) for binding sites at the ribosomal tunnel exit. Yet, whereas well-resolved structures for ribosome-bound RAC, SRP and Sec61, are available, structural information on the mode of ribosome interaction of eukaryotic MetAPs or of the five cotranslationally active NATs is only available for NatA. Here, we present cryo-EM structures of yeast Map1 and NatB bound to ribosome-nascent chain complexes. Map1 is mainly associated with the dynamic rRNA expansion segment ES27a, thereby kept at an ideal position below the tunnel exit to act on the emerging substrate nascent chain. For NatB, we observe two copies of the NatB complex. NatB-1 binds directly below the tunnel exit, again involving ES27a, and NatB-2 is located below the second universal adapter site (eL31 and uL22). The binding mode of the two NatB complexes on the ribosome differs but overlaps with that of NatA and Map1, implying that NatB binds exclusively to the tunnel exit. We further observe that ES27a adopts distinct conformations when bound to NatA, NatB, or Map1, together suggesting a contribution to the coordination of a sequential activity of these factors on the emerging nascent chain at the ribosomal exit tunnel.

HIV pre-exposure prophylaxis was associated with no impact on sexually transmitted infection prevalence in a high-prevalence population of predominantly men who have sex with men, Germany, 2018 to 2019.

IntroductionDespite increased use of pre-exposure prophylaxis (PrEP) in Germany, HIV infection rates are not declining and little is known about how this prevention method affects the prevalence of sexually transmitted infections (STI) among men who have sex with men (MSM).AimWe studied, in a large multicentre cohort, STI point prevalence, co-infection rates, anatomical location and influence of PrEP.MethodsThe BRAHMS study was a prospective cohort study conducted at 10 sites in seven major German cities that enrolled MSM reporting increased sexual risk behaviour. At screening visits, MSM were tested for Mycoplasma genitalium (MG), Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Treponema pallidum (TP), and given a behavioural questionnaire. With binomial regression, we estimated prevalence ratios (PR) and 95% confidence intervals (CI) for the association of PrEP and STI.ResultsWe screened 1,043 MSM in 2018 and 2019, with 53.0% currently using PrEP. At screening, 370 participants (35.5%) had an STI. The most common pathogen was MG in 198 (19.0%) participants, followed by CT (n = 133; 12.8%), NG (n = 105; 10.1%) and TP (n = 37; 3.5%). Among the 370 participants with at least one STI, 14.6% (n = 54) reported STI-related symptoms. Infection prevalence was highest at anorectal site (13.4% MG, 6.5% NG, 10.2% CT). PrEP use was not statistically significant in adjusted models for STI (PR: 1.10; 95% CI: 0.91-1.32), NG/CT, only NG or only CT.ConclusionsPrevalence of asymptomatic STI was high, and PrEP use did not influence STI prevalence in MSM eligible for PrEP according to national guidelines.

Establishing a Valid, Reliable, and Efficient Chart Review Process for Research in Pediatric Integrated Primary Care Psychology.

Retrospective chart review is an accessible form of research that is commonly used across medical fields but is underutilized in behavioral health. As a relatively newer area of research, the field of pediatric integrated primary care (IPC) would particularly benefit from guidelines for conducting a methodologically sound chart review study. Here, we use our experiences building a chart review procedure for a pediatric IPC research project to offer strategies for optimizing reliability (consistency), validity (accuracy), and efficiency. We aim to provide guidance for conducting a chart review study in the specific setting of pediatric IPC so that researchers can apply this methodology toward generating research in this field.

Ribosome-NatA architecture reveals that rRNA expansion segments coordinate N-terminal acetylation.

The majority of eukaryotic proteins are N-terminally α-acetylated by N-terminal acetyltransferases (NATs). Acetylation usually occurs co-translationally and defects have severe consequences. Nevertheless, it is unclear how these enzymes act in concert with the translating ribosome. Here, we report the structure of a native ribosome-NatA complex from Saccharomyces cerevisiae. NatA (comprising Naa10, Naa15 and Naa50) displays a unique mode of ribosome interaction by contacting eukaryotic-specific ribosomal RNA expansion segments in three out of four binding patches. Thereby, NatA is dynamically positioned directly underneath the ribosomal exit tunnel to facilitate modification of the emerging nascent peptide chain. Methionine amino peptidases, but not chaperones or signal recognition particle, would be able to bind concomitantly. This work assigns a function to the hitherto enigmatic ribosomal RNA expansion segments and provides mechanistic insights into co-translational protein maturation by N-terminal acetylation.

Lithium and glutamine synthetase: Protective effects following stress.

Even though lithium is widely used as treatment for mood disorders, the exact mechanisms of lithium in the brain remain unknown. A potential mechanism affects the downstream target of the Wnt/ß-catenin signaling pathway, specifically glutamine synthetase (GS). Here, we investigate the effect of lithium on GS-promoter activity in the brain. Over seven days, B6C3H-Glultm(T2A-LacZ) mice that carry LacZ as a reporter gene fused to the GS-promotor received either daily intraperitoneal injections of lithium carbonate (25 mg/kg) or NaCl, or no treatment. Following histochemical staining of ß-galactosidase relative GS-promotor activity was measured by analyzing the intensity of the staining. Furthermore cell counts were conducted. GS-promotor activity was significantly decreased in female compared to male mice. Treatment group differences were only found in male hippocampi, with increased activity after NaCl treatment compared to both the lithium treatment and no treatment. Lithium treatment increased the overall number of cells in the CA1 region in males. Daily injections of NaCl might have been sufficient to induce stress-related GS-promotor activity changes in male mice; however, lithium was able to reverse the effect. Taken together, the current study indicates that lithium acts to prevent stress, rather affecting general GS-promoter activity.

Interleukin-4 is a participant in the regulation of depressive-like behavior.

Inflammatory immune activation has been frequently associated with the development of major depression. Microglia might serve as an important interface in this immune system-to-brain communication. Interleukin-4, the major Th2 type cytokine, might be protective against depression due to its ability to counter-regulate inflammation and to inhibit serotonin transporter activity. By using an Interferon-α mouse model, we show that a decreased IL-4 responsiveness of microglia was specifically related to the development of depressive-like behavior. IL-4 deficient mice in a BALB/cJ background showed a considerable increase of depressive-like behavior in the forced swim (FST) and tail suspension test (TST) and reduced avoidance behavior in an active avoidance task. Prior conditioning with unescapable foot shocks further decreased avoidance behavior (learned helplessness) but to a similar level as in the wild type strain. IFN-α treatment was not able to further enhance the already increased level of depressive-like behavior in the FST and TST. Thus, IL-4 seems to be a critical participant in the regulation of depressive-like behavior in an untreated baseline condition. Increase of depressive-like behavior during inflammation in wild-type mice might be mediated to some extent by a reduction of IL-4 signaling.