The human SWI/SNF-B chromatin-remodeling complex is related to yeast Rsc and localizes at kinetochores of mitotic chromosomes

The SWI/SNF family of chromatin-remodeling complexes facilitates gene expression by helping transcription factors gain access to their targets in chromatin. SWI/SNF and Rsc are distinctive members of this family from yeast. They have similar protein components and catalytic activities but differ in biological function. Rsc is required for cell cycle progression through mitosis, whereas SWI/SNF is not. Human complexes of this family have also been identified, which have often been considered related to yeast SWI/SNF. However, all human subunits identified to date are equally similar to components of both SWI/SNF and Rsc, leaving open the possibility that some or all of the human complexes are rather related to Rsc. Here, we present evidence that the previously identified human SWI/SNF-B complex is indeed of the Rsc type. It contains six components conserved in both Rsc and SWI/SNF. Importantly, it has a unique subunit, BAF180, that harbors a distinctive set of structural motifs characteristic of three components of Rsc. Of the two mammalian ATPases known to be related to those in the yeast complexes, human SWI/SNF-B contains only the homolog that functions like Rsc during cell growth. Immunofluorescence studies with a BAF180 antibody revealed that SWI/SNF-B localizes at the kinetochores of chromosomes during mitosis. Our data suggest that SWI/SNF-B and Rsc represent a novel subfamily of chromatin-remodeling complexes conserved from yeast to human, and could participate in cell division at kinetochores of mitotic chromosomes.

Selective response of ternary complex factor Sap1a to different mitogen-activated protein kinase subgroups.

Mitogenic and stres signals results in the activation of extracellular signal-regulated kinases (ERKs) and stress-activated protein kinase/c-Jun N-terminal kinases (SAPK/JNKs), respectively, which are two subgroups of the mitogen-activated protein kinases. A nuclear target of mitogen-activated protein (MAP) kinases is the ternary complex factor Elk-1, which underlies its involvement in the regulation of c-fos gene expression by mitogenic and stress signals. A second ternary complex factor, Sap1a, is coexpressed with Elk-1 in several cell types and shares attributes of Elk-1, the significance of which is not clear. Here we show that Sap1a is phosphorylated efficiently by ERKs but not by SAPK/JNKs. Serum response factor-dependent ternary complex formation by Sap1a is stimulated by ERK phosphorylation but not by SAPK/JNKs. Moreover, Sap1a-mediated transcription is activated by mitogenic signals but not by cell stress. These results suggest that Sap1a and Elk-1 have distinct physiological functions.

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

Upon photolysis at 355 nm, dioxygen is released from a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)cobalt-(III)] complex in aqueous solutions and at physiological pH with a quantum yield of 0.04. The [Co(bpy)2(H2O)2]2+ (bpy = bipyridyl) photoproduct was generated on a nanosecond or faster time scale as determined by time-resolved optical absorption spectroscopy. A linear correspondence between the spectral changes and the oxygen production indicates that O2 is released on the same time scale. Oxyhemoglobin was formed from deoxyhemoglobin upon photodissociation of the (mu-peroxo) (mu-hydroxo)bis[bis(bipyridyl)cobalt(III)] complex, verifying that dioxygen is a primary photoproduct. This complex and other related compounds provide a method to study fast biological reactions involving O2, such as the reduction of dioxygen to water by cytochrome oxidase.

Characterizing the satellites of massive galaxies up to z ∼ 2: young populations to build the outskirts of nearby massive galaxies

The accretion of minor satellites is currently proposed as the most likely mechanism to explain the significant size evolution of the massive galaxies during the last ∼10 Gyr. In this paper, we investigate the rest-frame colours and the average stellar ages of satellites found around massive galaxies (M_star ∼ 10^11 M_⊙) since z ∼ 2. We find that the satellites have bluer colours than their central galaxies. When exploring the stellar ages of the galaxies, we find that the satellites have similar ages to the massive galaxies that host them at high redshifts, while at lower redshifts they are, on average, ≳1.5 Gyr younger. If our satellite galaxies create the envelope of nearby massive galaxies, our results would be compatible with the idea that the outskirts of those galaxies are slightly younger, metal-poorer and with lower [α/Fe] abundance ratios than their inner regions.

Pion-kaon scattering amplitude constrained with forward dispersion relations up to 1.6 GeV

In this work we provide simple and precise parametrizations of the existing πK scattering data from threshold up to 1.6 GeV, which are constrained to satisfy forward dispersion relations as well as three additional threshold sum rules. We also provide phenomenological values of the threshold parameters and of the resonance poles that appear in elastic scattering.

Setting Congress Up to Fail

In Shelby County v. Holder the Supreme Court invalidated key provisions of the Voting Rights Act of 1965 based on Congress’s failure to justify the formula used to determine which jurisdictions would be subject to the Act’s pre-clearance requirement of submitting all changes to voting procedures to the Justice Department for prior approval. This short essay explores one problematic feature of the Court’s analysis: its refusal to consider the legislative record as adequate because it was created to justify the coverage formula after the fact, rather than to facilitate deliberation on the coverage formula before a decision had been made. This reasoning essentially imports from administrative law a rule called the Chenery principle, and as this essay explains, it does so without justification. The differences between administrative and legislative decision making processes compel different treatment by the courts, and treating legislative records like administrative ones, in essence, asks of Congress something it is institutionally ill-equipped to perform. It sets Congress up to fail.

Vote of the Corporation continuing the salary of the President up to the next commencement,

This folder contains two nineteenth-century handwritten copies of the vote.