A Specialized Nucleosome Modulates Transcription Factor Access to a C. glabrata Metal Responsive Promoter

AbstractThe ability of DNA binding transcription factors to access cis-acting promoter elements is critical for transcriptional responses. We demonstrate that rapid transcriptional autoactivation by the Amt1 Cu metalloregulatory transcription factor from the opportunistic pathogenic yeast Candida glabrata is dependent on rapid metal-induced DNA binding to a single metal response element (MRE). In vivo footprinting and chromatin-mapping experiments demonstrate that the MRE and a homopolymeric (dA • dT) element adjacent to the MRE are packaged into a positioned nucleosome that exhibits homopolymeric (dA • dT)-dependent localized distortion. This distortion is critical for rapid Amt1 binding to the MRE, for Cu-dependent AMT1 gene transcription, and for C. glabrata cells to mount a rapid transcriptional response to Cu for normal metal detoxification. The AMT1 promoter represents a novel class of specialized nucleosomal structures that links rapid transcriptional responses to the biology of metal homeostasis

On the stability and instability of Kelvin-Stuart cat's eyes flows

Kelvin-Stuart vortices are classical mixing layer flows with many applications in fluid mechanics, plasma physics and astrophysics. We prove that the whole family of Kelvin-Stuart vortices is nonlinearly stable for co-periodic perturbations, and linearly unstable for multi-periodic or modulational perturbations. This verifies a long-standing conjecture since the discovery of the Kelvin-Stuart cat's eyes flows in the 1960s. Kelvin-Stuart cat's eyes also appear as magnetic islands which are magnetostatic equilibria for the 2D ideal MHD equations in plasmas. We prove nonlinear stability of Kelvin-Stuart magnetic islands for co-periodic perturbations, and give the first rigorous proof of the coalescence instability, which is important for magnetic reconnection.Comment: 122 page

Nonlinear stability of non-rotating gaseous stars

For the non-rotating gaseous stars modeled by the compressible Euler-Poisson system with general pressure law, Lin and Zeng [18] proved a turning point principle, which gives the sharp linear stability/instability criteria for the non-rotating gaseous stars. In this paper, we prove that the sharp linear stability criterion for the non-rotating stars also implies nonlinear orbital stability against general perturbations provided the global weak solutions exist. If the perturbations are further restricted to be spherically symmetric, then nonlinear stability holds true unconditionally in the sense that the existence of global weak solutions near the non-rotating star can be proved.Comment: 30 page