Architecture of the type IVa pilus machine

Many bacteria, including important pathogens, move by projecting grappling-hook–like extensions called type IV pili from their cell bodies. After these pili attach to other cells or objects in their environment, the bacteria retract the pili to pull themselves forward. Chang et al. used electron cryotomography of intact cells to image the protein machines that extend and retract the pili, revealing where each protein component resides. Putting the known structures of the individual proteins in place like pieces of a three-dimensional puzzle revealed insights into how the machine works, including evidence that ATP hydrolysis by cytoplasmic motors rotates a membrane-embedded adaptor that slips pilin subunits back and forth from the membrane onto the pilus

PilY1 and minor pilins form a complex priming the type IVa pilus in Myxococcus xanthus

Type IVa pili are ubiquitous and versatile bacterial cell surface filaments that undergo cycles of extension, adhesion and retraction powered by the cell-envelope spanning type IVa pilus machine (T4aPM). The overall architecture of the T4aPM and the location of 10 conserved core proteins within this architecture have been elucidated. Here, using genetics, cell biology, proteomics and cryo-electron tomography, we demonstrate that the PilY1 protein and four minor pilins, which are widely conserved in T4aP systems, are essential for pilus extension in Myxococcus xanthus and form a complex that is an integral part of the T4aPM. Moreover, these proteins are part of the extended pilus. Our data support a model whereby the PilY1/minor pilin complex functions as a priming complex in T4aPM for pilus extension, a tip complex in the extended pilus for adhesion, and a cork for terminating retraction to maintain a priming complex for the next round of extension

PilY1 and minor pilins form a complex priming the type IVa pilus in Myxococcus xanthus

Type IVa pili are ubiquitous and versatile bacterial cell surface filaments that undergo cycles of extension, adhesion and retraction powered by the cell-envelope spanning type IVa pilus machine (T4aPM). The overall architecture of the T4aPM and the location of 10 conserved core proteins within this architecture have been elucidated. Here, using genetics, cell biology, proteomics and cryo-electron tomography, we demonstrate that the PilY1 protein and four minor pilins, which are widely conserved in T4aP systems, are essential for pilus extension in Myxococcus xanthus and form a complex that is an integral part of the T4aPM. Moreover, these proteins are part of the extended pilus. Our data support a model whereby the PilY1/minor pilin complex functions as a priming complex in T4aPM for pilus extension, a tip complex in the extended pilus for adhesion, and a cork for terminating retraction to maintain a priming complex for the next round of extension

Breast Cancer Index is a predictive biomarker of treatment benefit and outcome from extended tamoxifen therapy: final analysis of the Trans-aTTom study

PURPOSE: The Breast Cancer Index (BCI) HOXB13/IL17BR (H/I) ratio predicts benefit from extended endocrine therapy in hormone receptor–positive (HR(+)) early-stage breast cancer. Here, we report the final analysis of the Trans-aTTom study examining BCI (H/I)'s predictive performance. EXPERIMENTAL DESIGN: BCI results were available for 2,445 aTTom trial patients. The primary endpoint of recurrence-free interval (RFI) and secondary endpoints of disease-free interval (DFI) and disease-free survival (DFS) were examined using Cox proportional hazards regression and log-rank test. RESULTS: Final analysis of the overall study population (N = 2,445) did not show a significant improvement in RFI with extended tamoxifen [HR, 0.90; 95% confidence interval (CI), 0.69–1.16; P = 0.401]. Both the overall study population and N0 group were underpowered due to the low event rate in the N0 group. In a pre-planned analysis of the N(+) subset (N = 789), BCI (H/I)-High patients derived significant benefit from extended tamoxifen (9.7% absolute benefit: HR, 0.33; 95% CI, 0.14–0.75; P = 0.016), whereas BCI (H/I)-Low patients did not (−1.2% absolute benefit; HR, 1.11; 95% CI, 0.76–1.64; P = 0.581). A significant treatment-to-biomarker interaction was demonstrated on the basis of RFI, DFI, and DFS (P = 0.037, 0.040, and 0.025, respectively). BCI (H/I)-High patients remained predictive of benefit from extended tamoxifen in the N(+)/HER2(−) subgroup (9.4% absolute benefit: HR, 0.35; 95% CI, 0.15–0.81; P = 0.047). A three-way interaction evaluating BCI (H/I), treatment, and HER2 status was not statistically significant (P = 0.849). CONCLUSIONS: Novel findings demonstrate that BCI (H/I) significantly predicts benefit from extended tamoxifen in HR(+) N(+) patients with HER2(−) disease. Moreover, BCI (H/I) demonstrates significant treatment to biomarker interaction across survival outcomes

Protein Pattern Formation

Protein pattern formation is essential for the spatial organization of many intracellular processes like cell division, flagellum positioning, and chemotaxis. A prominent example of intracellular patterns are the oscillatory pole-to-pole oscillations of Min proteins in \textit{E. coli} whose biological function is to ensure precise cell division. Cell polarization, a prerequisite for processes such as stem cell differentiation and cell polarity in yeast, is also mediated by a diffusion-reaction process. More generally, these functional modules of cells serve as model systems for self-organization, one of the core principles of life. Under which conditions spatio-temporal patterns emerge, and how these patterns are regulated by biochemical and geometrical factors are major aspects of current research. Here we review recent theoretical and experimental advances in the field of intracellular pattern formation, focusing on general design principles and fundamental physical mechanisms.Comment: 17 pages, 14 figures, review articl

Correlated cryogenic photoactivated localization microscopy and cryo-electron tomography

Cryo-electron tomography (CET) produces three-dimensional images of cells in a near-native state at macromolecular resolution, but identifying structures of interest can be challenging. Here we describe a correlated cryo-PALM (photoactivated localization microscopy)-CET method for localizing objects within cryo-tomograms to beyond the diffraction limit of the light microscope. Using cryo-PALM-CET, we identified multiple and new conformations of the dynamic type VI secretion system in the crowded interior of Myxococcus xanthus

Breast cancer index predicts extended endocrine benefit to individualize selection of patients with HR+ early-stage breast cancer for 10 years of endocrine therapy

Purpose: Individualized selection of patients with early-stage hormone receptor-positive (HR+) breast cancer for extended endocrine therapy (EET) is required to balance modest gains in outcome with toxicities of prolonged use. This study examined the Breast Cancer Index [BCI; HOXB13/IL17BR ratio (H/I)] as a predictive biomarker of EET benefit in patients from the Investigation on the Duration of Extended Adjuvant Letrozole trial.Experimental Design: BCI was tested in primary tumor specimens from 908 patients randomized to receive 2.5 versus 5 years of extended letrozole. The primary endpoint was recurrence-free interval. Cox models and likelihood ratios tested the interaction between HET and BCI (H/I).Results: BCI (H/I)-high significantly predicted benefit from extended letrozole in the overall cohort [HR 0.42; 95% confidence interval (CI), 0.21-0.84; P = 0.011] and any aromatase inhibitor subset [HR 0.34; 95% CI, 0.16-0.73; P - 0.004), whereas BCI (H/I)-low patients did not derive significant benefit (HR 0.95; 95% CI, 0.58-1.56; P - 0.84 and HR 0.90; 95% CI, 053-1.55; P - 0.71, respectively) treatment to hiomarker interaction was significant (P = 0.045, P = 0.025, respectively). BCI identified approximately 50% of patients with clinically high-risk disease that did not benefit, and with clinically low-risk disease that derived significant benefit, from an additional 2.5 years of EEL.Conclusions: BCI (H/I) predicted preferential benefit from 5 versus 2.5 years of EET and identified patients with improved outcomes from completing 10 years of adjuvant endocrine therapy. Findings expand the clinical utility of BCI (H/I) to a broader range of patients and beyond prognostic risk factors as a predictive endocrine response biomarker for early-stage HR+ breast cancer.Surgical oncolog

The Phosphatomes of the Multicellular Myxobacteria Myxococcus xanthus and Sorangium cellulosum in Comparison with Other Prokaryotic Genomes

BACKGROUND: Analysis of the complete genomes from the multicellular myxobacteria Myxococcus xanthus and Sorangium cellulosum identified the highest number of eukaryotic-like protein kinases (ELKs) compared to all other genomes analyzed. High numbers of protein phosphatases (PPs) could therefore be anticipated, as reversible protein phosphorylation is a major regulation mechanism of fundamental biological processes. METHODOLOGY: Here we report an intensive analysis of the phosphatomes of M. xanthus and S. cellulosum in which we constructed phylogenetic trees to position these sequences relative to PPs from other prokaryotic organisms. PRINCIPAL FINDINGS: PREDOMINANT OBSERVATIONS WERE: (i) M. xanthus and S. cellulosum possess predominantly Ser/Thr PPs; (ii) S. cellulosum encodes the highest number of PP2c-type phosphatases so far reported for a prokaryotic organism; (iii) in contrast to M. xanthus only S. cellulosum encodes high numbers of SpoIIE-like PPs; (iv) there is a significant lack of synteny among M. xanthus and S. cellulosum, and (v) the degree of co-organization between kinase and phosphatase genes is extremely low in these myxobacterial genomes. CONCLUSIONS: We conclude that there has been a greater expansion of ELKs than PPs in multicellular myxobacteria