Dark Energy Survey Year 1 Results: Cosmological Constraints from Cluster Abundances, Weak Lensing, and Galaxy Correlations.

We present the first joint analysis of cluster abundances and auto or cross-correlations of three cosmic tracer fields: galaxy density, weak gravitational lensing shear, and cluster density split by optical richness. From a joint analysis (4×2pt+N) of cluster abundances, three cluster cross-correlations, and the auto correlations of the galaxy density measured from the first year data of the Dark Energy Survey, we obtain Ω_{m}=0.305_{-0.038}^{+0.055} and σ_{8}=0.783_{-0.054}^{+0.064}. This result is consistent with constraints from the DES-Y1 galaxy clustering and weak lensing two-point correlation functions for the flat νΛCDM model. Consequently, we combine cluster abundances and all two-point correlations from across all three cosmic tracer fields (6×2pt+N) and find improved constraints on cosmological parameters as well as on the cluster observable-mass scaling relation. This analysis is an important advance in both optical cluster cosmology and multiprobe analyses of upcoming wide imaging surveys.

Detection of CMB-Cluster Lensing using Polarization Data from SPTpol.

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes QU map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500 deg^{2} survey at the locations of roughly 18 000 clusters with richness λ≥10 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8σ. The mean stacked mass of the selected sample is found to be (1.43±0.40)×10^{14}M_{⊙} which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements.

Characterization of an atypical superoxide dismutase from Sinorhizobium meliloti.

Sinorhizobium meliloti Rm5000 is an aerobic bacterium that can live free in the soil or in symbiosis with the roots of leguminous plants. A single detectable superoxide dismutase (SOD) was found in free-living growth conditions. The corresponding gene was isolated from a genomic library by using a sod fragment amplified by PCR from degenerate primers as a probe. The sodA gene was located in the chromosome. It is transcribed monocistronically and encodes a 200-amino-acid protein with a theoretical M(r) of 22,430 and pI of 5. 8. S. meliloti SOD complemented a deficient E. coli mutant, restoring aerobic growth of a sodA sodB recA strain, when the gene was expressed from the synthetic tac promoter but not from its own promoter. Amino acid sequence alignment showed great similarity with Fe-containing SODs (FeSODs), but the enzyme was not inactivated by H(2)O(2). The native enzyme was purified and found to be a dimeric protein, with a specific activity of 4,000 U/mg. Despite its Fe-type sequence, atomic absorption spectroscopy showed manganese to be the cofactor (0.75 mol of manganese and 0.24 mol of iron per mol of monomer). The apoenzyme was prepared from crude extracts of S. meliloti. Activity was restored by dialysis against either MnCl(2) or Fe(NH(4))(2)(SO(4))(2), demonstrating the cambialistic nature of the S. meliloti SOD. The recovered activity with manganese was sevenfold higher than with iron. Both reconstituted enzymes were resistant to H(2)O(2). Sequence comparison with 70 FeSODs and MnSODs indicates that S. meliloti SOD contains several atypical residues at specific sites that might account for the activation by manganese and resistance to H(2)O(2) of this unusual Fe-type SOD.

Evidence for different MCM subcomplexes with differential binding to chromatin in Xenopus.

MCM proteins are molecular components of the DNA replication licensing system in Xenopus. These proteins comprise a conserved family made up of six distinct members which have been found to associate in large protein complexes. We have used a combination of biochemical and cytological methods to study the association of soluble and chromatin-bound Xenopus MCM proteins during the cell cycle. In interphase, soluble MCM proteins are found organized in a core salt-resistant subcomplex that includes MCM subunits which are known to have high affinity for histones. The interphasic complex is modified at mitosis and the subunit composition of the resulting mitotic subcomplexes is distinct, indicating that the stability of the MCM complex is under cell cycle control. Moreover, we provide evidence that the binding of MCM proteins to chromatin may occur in sequential steps involving the loading of distinct MCM subunits. Comparative analysis of the chromatin distribution of MCM2, 3, and 4 shows that the binding of MCM4 is distinct from that of MCM2 and 3. Altogether, these data suggest that licensing of chromatin by MCMs occurs in an ordered fashion involving discrete subcomplexes.

Selective and rapid nuclear translocation of a c-Myc-containing complex after fertilization of Xenopus laevis eggs.

We report here unusual features of c-Myc specific to early embryonic development in Xenopus laevis, a period characterized by generalized transcriptional quiescence and rapid biphasic cell cycles. Two c-Myc protein forms, p61 and p64, are present in large amounts in the oocyte as well as during early development. In contrast, only p64 c-Myc is present in Xenopus somatic cells. p61 c-Myc is the direct translation product from both endogenous c-myc mRNAs and c-myc recombinant DNA. It is converted to the p64 c-Myc form after introduction into an egg extract, in the presence of phosphatase inhibitors. p61 and p64 belong to two distinct complexes localized in the cytoplasm of the oocyte. A 15S complex contains p64 c-Myc, and a 17.4S complex contains p61 c-Myc. Fertilization triggers the selective and total entry of only p64 c-Myc into the nucleus. This translocation occurs in a nonprogressive manner and is completed during the first cell cycles. This phenomenon results in an exceptionally high level of c-Myc in the nucleus, which returns to a somatic cell-like level only at the end of the blastulation period. During early development, when the entire embryonic genome is transcriptionally inactive, c-Myc does not exhibit a DNA binding activity with Max. Moreover, embryonic nuclei not only prevent the formation of c-Myc/Max complexes but also dissociate such preformed complexes. These peculiar aspects of c-Myc behavior suggest a function that could be linked to the rapid DNA replication cycles occurring during the early cell cycles rather than a function involving transcriptional activity.

Production of a functional full-length Xenopus laevis c-Myc protein in insect cells.

C-Myc is a nuclear phosphoprotein whose normal cellular function has not yet been clearly defined. Studies with this protein have always been constrained by the difficulty of obtaining full-length c-Myc in an active form, whatever the expression system used. We report here experimental conditions optimized to increase the solubility and the purification of c-Myc in a baculovirus expression system. Such conditions allow the production of both soluble and active full-length c-Myc. Interestingly, soluble c-Myc is found associated with a 500-kDa high-molecular-mass complex comparable to that found in human and Xenopus laevis embryos, and which may be required for its function in vivo.