RecQ-core of BLM unfolds telomeric G-quadruplex in the absence of ATP

Various helicases and single-stranded DNA (ssDNA) binding proteins are known to destabilize G-quadruplex (GQ) structures, which otherwise result in genomic instability. Bulk biochemical studies have shown that Bloom helicase (BLM) unfolds both intermolecular and intramolecular GQ in the presence of ATP. Using single molecule FRET, we show that binding of RecQ-core of BLM (will be referred to as BLM) to ssDNA in the vicinity of an intramolecular GQ leads to destabilization and unfolding of the GQ in the absence of ATP. We show that the efficiency of BLM-mediated GQ unfolding correlates with the binding stability of BLM to ssDNA overhang, as modulated by the nucleotide state, ionic conditions, overhang length and overhang directionality. In particular, we observed enhanced GQ unfolding by BLM in the presence of non-hydrolysable ATP analogs, which has implications for the underlying mechanism. We also show that increasing GQ stability, via shorter loops or higher ionic strength, reduces BLM-mediated GQ unfolding. Finally, we show that while WRN has similar activity as BLM, RecQ and RECQ5 helicases do not unfold GQ in the absence of ATP at physiological ionic strength. In summary, our study points to a novel and potentially very common mechanism of GQ destabilization mediated by proteins binding to the vicinity of these structures.     

When the Body Hides the Ancestry: Phylogeny of Morphologically Modified Epizoic Earwigs Based on Molecular Evidence

Here, we present a study regarding the phylogenetic positions of two enigmatic earwig lineages whose unique phenotypic traits evolved in connection with ectoparasitic relationships with mammals. Extant earwigs (Dermaptera) have traditionally been divided into three suborders: the Hemimerina, Arixeniina, and Forficulina. While the Forficulina are typical, well-known, free-living earwigs, the Hemimerina and Arixeniina are unusual epizoic groups living on molossid bats (Arixeniina) or murid rodents (Hemimerina). The monophyly of both epizoic lineages is well established, but their relationship to the remainder of the Dermaptera is controversial because of their extremely modified morphology with paedomorphic features. We present phylogenetic analyses that include molecular data (18S and 28S ribosomal DNA and histone-3) for both Arixeniina and Hemimerina for the first time. This data set enabled us to apply a rigorous cladistics approach and to test competing hypotheses that were previously scattered in the literature. Our results demonstrate that Arixeniidae and Hemimeridae belong in the dermapteran suborder Neodermaptera, infraorder Epidermaptera, and superfamily Forficuloidea. The results support the sister group relationships of Arixeniidae+Chelisochidae and Hemimeridae+Forficulidae. This study demonstrates the potential for rapid and substantial macroevolutionary changes at the morphological level as related to adaptive evolution, in this case linked to the utilization of a novel trophic niche based on an epizoic life strategy. Our results also indicate that the evolutionary consequences of the transition to an ectoparazitic mode of living, which is extremely rare in earwigs, have biased previous morphology-based hypotheses regarding the phylogeny of this insect group.     

Tissue and serum levels of principal androgens in benign prostatic hyperplasia and prostate cancer

Androgens are considered to play a substantial role in pathogenesis of both benign prostatic hyperplasia (BPH) and prostate cancer. The importance of determination of androgen levels in tissue and serum for cancer progression and prognosis has been poorly understood. The aim of study was to find out hormonal differences in both diseases, their correlations between intraprostatic and serum levels and predicted value of their investigation. Testosterone, dihydrotestosterone, androstenedione and also epitestosterone were determined in prostate tissue from 57 patients who underwent transvesical prostatectomy for BPH and 121 patients after radical prostatectomy for prostate cancer. In 75 subjects with cancer and 51 with BPH the serum samples were analyzed for testosterone, dihydrotestosterone and SHBG. Significantly higher intraprostatic androgen concentrations, i.e. 8.85+/-6.77 versus 6.44+/-6.43 pmol/g, p<0.01 for dihydrotestosterone, and 4.61+/-7.02 versus 3.44+/-4.53 pmol/g, p<0.05 for testosterone, respectively, were found in patients with prostate cancer than in BPH. Higher levels in cancer tissue were found also for epitestosterone. However, no differences were found in serum levels. Highly significant correlations occurred between all pairs of intraprostatic androgens and also epitestosterone as well as between serum testosterone and dihydrotestosterone (p<0.001) in both BPH and cancer groups. Correlation was not found between corresponding tissue and serum testosterone and dihydrotestosterone, either in benign or cancer samples. The results point to importance of intraprostatic hormone levels for evaluation of androgen status of patients, contrasting to a low value of serum hormone measurement.     

Membrane microdomains in immunoreceptor signaling

Membrane microdomains denoted commonly as lipid rafts (or membrane rafts) have been implicated in T-cell receptor (TCR), and more generally immunoreceptor, signaling for over 25 years. However, this area of research has been complicated by doubts about the real nature (and even existence) of these membrane entities, especially because of methodological problems connected with possible detergent artefacts. Recent progress in biophysical approaches and functional studies of raft resident proteins apparently clarified many controversial aspects in this area. At present, the prevailing view is that these membrane microdomains are indeed involved in many aspects of cell biology, including immunoreceptor signaling. Moreover, several other types of raft-like microdomains (perhaps better termed nanodomains) have been described, which apparently also play important biological roles.     

Chromosome-wide characterization of meiotic noncrossovers (gene conversions) in mouse hybrids

During meiosis, the recombination-initiating DNA double-strand breaks (DSBs) are repaired by crossovers or noncrossovers (gene conversions). While crossovers are easily detectable, noncrossover identification is hampered by the small size of their converted tracts and the necessity of sequence polymorphism. We report identification and characterization of a mouse chromosome-wide set of noncrossovers by next-generation sequencing of 10 mouse intersubspecific chromosome substitution strains. Based on 94 identified noncrossovers, we determined the mean length of a conversion tract to be 32 bp. The spatial chromosome-wide distribution of noncrossovers and crossovers significantly differed, although both sets overlapped the known hotspots of PRDM9-directed histone methylation and DNA DSBs, thus supporting their origin in the standard DSB repair pathway. A significant deficit of noncrossovers descending from asymmetric DSBs proved their proposed adverse effect on meiotic recombination and pointed to sister chromatids as an alternative template for their repair. The finding has implications for the molecular mechanism of hybrid sterility in mice from crosses between closely related Mus musculus musculus and Mus musculus domesticus subspecies.     

Tuberosphere and bulk soil microbial communities in fields differing in common scab severity are distinguished by soil chemistry and interactions with pathogens

Plant and Soil - Common scab of potatoes (CS) is influenced by plant-microbe-soil interactions, which are locally specific. The study aims to identify any common trends in such interactions across...     

Structural basis of RNA recognition by the SARS-CoV-2 nucleocapsid phosphoprotein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the coronavirus disease 2019 (COVID-19). SARS-CoV-2 is a single-stranded positive-sense RNA virus. Like other coronaviruses, SARS-CoV-2 has an unusually large genome that encodes four structural proteins and sixteen nonstructural proteins. The structural nucleocapsid phosphoprotein N is essential for linking the viral genome to the viral membrane. Both N-terminal RNA binding (N-NTD) and C-terminal dimerization domains are involved in capturing the RNA genome and, the intrinsically disordered region between these domains anchors the ribonucleoprotein complex to the viral membrane. Here, we characterized the structure of the N-NTD and its interaction with RNA using NMR spectroscopy. We observed a positively charged canyon on the surface of the N-NTD that might serve as a putative RNA binding site similarly to other coronaviruses. The subsequent NMR titrations using single-stranded and double-stranded RNA revealed a much more extensive U-shaped RNA-binding cleft lined with regularly distributed arginines and lysines. The NMR data supported by mutational analysis allowed us to construct hybrid atomic models of the N-NTD/RNA complex that provided detailed insight into RNA recognition.     

SCIMP, a transmembrane adaptor protein involved in major histocompatibility complex class II signaling

Formation of the immunological synapse between an antigen-presenting cell (APC) and a T cell leads to signal generation in both cells involved. In T cells, the lipid raft-associated transmembrane adaptor protein LAT plays a central role. Its phosphorylation is a crucial step in signal propagation, including the calcium response and mitogen-activated protein kinase activation, and largely depends on its association with the SLP76 adaptor protein. Here we report the discovery of a new palmitoylated transmembrane adaptor protein, termed SCIMP. SCIMP is expressed in B cells and other professional APCs and is localized in the immunological synapse due to its association with tetraspanin-enriched microdomains. In B cells, it is constitutively associated with Lyn kinase and becomes tyrosine phosphorylated after major histocompatibility complex type II (MHC-II) stimulation. When phosphorylated, SCIMP binds to the SLP65 adaptor protein and also to the inhibitory kinase Csk. While the association with SLP65 initiates the downstream signaling cascades, Csk binding functions as a negative regulatory loop. The results suggest that SCIMP is involved in signal transduction after MHC-II stimulation and therefore serves as a regulator of antigen presentation and other APC functions.