An Investigation of Sloan Digital Sky Survey Imaging Data and Multi-Band Scaling Relations of Spiral Galaxies (with Dynamical Information)

We have compiled a sample of 3041 spiral galaxies with multi-band gri imaging from the Sloan Digital Sky Survey (SDSS) Data Release 7 and available galaxy rotational velocities derived from HI line widths. We compare the data products provided through the SDSS imaging pipeline with our own photometry of the SDSS images, and use the velocities (V) as an independent metric to determine ideal galaxy sizes (R) and luminosities (L). Our radial and luminosity parameters improve upon the SDSS DR7 Petrosian radii and luminosities through the use of isophotal fits to the galaxy images. This improvement is gauged via VL and RV relations whose respective scatters are reduced by ~8% and ~30% compared to similar relations built with SDSS parameters. The tightest VRL relations are obtained with the i-band radius, R235i, measured at 23.5 mag/arcsec^-2, and the luminosity L235i, measured within R235i. Our VRL scaling relations compare well, both in scatter and slope, with similar studies (such comparisons however depend sensitively on the nature and size of the compared samples). The typical slopes, b, and observed scatters, sigma, of the i-band VL, RL and RV relations are bVL=0.27+/-0.01, bRL=0.41+/-0.01, bRV=1.52+/-0.07, and sigmaVL=0.074, sigmaRL=0.071, sigmaRV=0.154 dex. Similar results for the SDSS g and r bands are also provided. Smaller scatters may be achieved for more pruned samples. We also compute scaling relations in terms of the baryonic mass (stars + gas), Mbar, ranging from 10^8.7 Msol to 10^11.6 Msol. Our baryonic velocity-mass (VM) relation has slope 0.29+/-0.01 and a measured scatter sigma_meas = 0.076 dex. While the observed VL and VM relations have comparable scatter, the stellar and baryonic VM relations may be intrinsically tighter, and thus potentially more fundamental, than other VL relations of spiral galaxies.Comment: Submitted to MNRAS, comments welcom

High-resolution profiling of homing endonuclease binding and catalytic specificity using yeast surface display

Experimental analysis and manipulation of protein–DNA interactions pose unique biophysical challenges arising from the structural and chemical homogeneity of DNA polymers. We report the use of yeast surface display for analytical and selection-based applications for the interaction between a LAGLIDADG homing endonuclease and its DNA target. Quantitative flow cytometry using oligonucleotide substrates facilitated a complete profiling of specificity, both for DNA-binding and catalysis, with single base pair resolution. These analyses revealed a comprehensive segregation of binding specificity and affinity to one half of the pseudo-dimeric interaction, while the entire interface contributed specificity at the level of catalysis. A single round of targeted mutagenesis with tandem affinity and catalytic selection steps provided mechanistic insights to the origins of binding and catalytic specificity. These methods represent a dynamic new approach for interrogating specificity in protein–DNA interactions

Regulation of Non-muscle Myosin II

Cell mechanics play a central role in motility, cytokinesis, and tissue architecture. The force-generating multimeric protein non-muscle myosin-II is a major player in the mechanics of both healthy and diseased cells, including those involved in certain cancers. Here, we explore factors that govern the assembly of myosin-II, explore its force dependence, and demonstrate that 14-3-3 proteins, which are highly conserved across phyla, are novel regulators of myosin-II assembly. Through a series of biochemical assays, we show that these proteins interact directly, with high affinity, and independently of phosphorylation. Furthermore, we show that both human and amoeboid myosin-IIs are tuned by their respective 14-3-3s, demonstrating evolutionary conservation of this pathway. These findings provide a means to integrate the observed shifts in 14-3-3 expression patterns with the prominent role of myosin-II in tumorigenesis. The 14-3-3 family comprises a group of small proteins that are essential, ubiquitous, and highly conserved across eukaryotes. Overexpression of the 14-3-3s sigma, epsilon, zeta, and eta correlates with high metastatic potential in multiple cancer types. Through studies in Dictyostelium (one 14-3-3, one myosin-II) and humans (seven 14-3-3s, three non-muscle myosin-IIs), we have uncovered the mechanism for myosin-II assembly regulation by 14-3-3s. In Dictyostelium, 14-3-3 promotes myosin-II turnover in the cell cortex and modulates cortical tension, cell shape, and cytokinesis. Here, in vitro assembly assays using purified myosin-II tail fragments and 14-3-3 demonstrate that this interaction is direct, phosphorylation-independent, and has a high effective affinity (KD ~300 nMdimer). All seven human 14-3-3s also affect the assembly of myosin-IIs to varying extents. Our findings demonstrate a novel mechanism for regulating myosin-II assembly that is mechanistically conserved across a billion years of evolution from amoebas to humans. We predict that altered 14-3-3 expression in humans inhibits the tumor suppressor myosin-II, contributing to the changes in cell mechanics observed in metastatic cancers

Targeting mechanoresponsive proteins in pancreatic cancer: 4-hydroxyacetophenone blocks dissemitation and invation by activating MYH14

Metastasis is complex, involving multiple genetic, epigenetic, biochemical, and physical changes in the cancer cell and its microenvironment. Cells with metastatic potential are often characterized by altered cellular contractility and deformability, lending them the flexibility to disseminate and navigate through different microenvironments. We demonstrate that mechanoresponsiveness is a hallmark of pancreatic cancer cells. Key mechanoresponsive proteins, those that accumulate in response to mechanical stress, specifically nonmuscle myosin IIA (MYH9) and IIC (MYH14), α-actinin 4, and filamin B, were highly expressed in pancreatic cancer as compared with healthy ductal epithelia. Their less responsive sister paralogs—myosin IIB (MYH10), α-actinin 1, and filamin A—had lower expression differential or disappeared with cancer progression. We demonstrate that proteins whose cellular contributions are often overlooked because of their low abundance can have profound impact on cell architecture, behavior, and mechanics. Here, the low abundant protein MYH14 promoted metastatic behavior and could be exploited with 4-hydroxyacetophenone (4-HAP), which increased MYH14 assembly, stiffening cells. As a result, 4-HAP decreased dissemination, induced cortical actin belts in spheroids, and slowed retrograde actin flow. 4-HAP also reduced liver metastases in human pancreatic cancer-bearing nude mice. Thus, increasing MYH14 assembly overwhelms the ability of cells to polarize and invade, suggesting targeting the mechanoresponsive proteins of the actin cytoskeleton as a new strategy to improve the survival of patients with pancreatic cancer