The stable maintenance of the 2m circle plasmid depends on its ability to overcome intrinsic maternal inheritance bias, which in yeast normally results in the failure to transmit DNA molecules efficiently to daughter cells. In addition to the plasmid proteins Rep1 and Rep2 acting on the plasmid DNA locus STB, it is likely that other chromosomally encoded yeast proteins are required. We have isolated mutants of yeast unable to maintain 2m and found that RSC2 is essential for 2m to overcome maternal inheritance bias. Rsc2 is part of a multisubunit RSC chromatin remodeling complex, and we show that in the absence of Rsc2 the chromatin structure of the STB region is significantly altered and the Rep1 protein loses its normal localization to subnuclear foci. Rsc1, a closely related homolog of Rsc2 present in an alternative form of the RSC complex, is not required for 2m maintenance and does not replace the requirement for Rsc2 when overexpressed. This represents the first specific role for Rsc2 that has been related to a change in chromatin structure, as well as the first direct evidence linking chromatin structure to 2m segregation.The 2m circle is a high-copy-number plasmid widespread in laboratory and industrial strains of Saccharomyces cerevisiae that has been used as a molecular model for aspects of cellular function such as DNA replication, gene transcription, and recombination, as well as the basis of yeast cloning vectors. High-copy-number plasmids carrying only replication origins show maternal inheritance bias (MIB) and are poorly segregated to daughter cells (31), whereas 2m and its derivatives are effectively segregated between mother and daughter cells at division (22). However, the mechanism by which 2m escapes MIB resulting in equal segregation is not fully understood, nor have all of the host components involved been identified. Of the four genes carried by the plasmid, REP1 and REP2 are necessary for MIB to be overcome, and their products act at the plasmid locus STB to confer plasmid stability (2,10,18,22,33,36). Within the nucleus, Rep1 and Rep2 proteins are localized into discrete foci (39) in which the plasmid is also colocalized (39, 52). These plasmid and protein foci are segregated in a manner similar to that of the chromosomes themselves, a finding consistent with the observation that the 2m plasmid is packaged into nucleosomes (50). Thus, the plasmid may be exploiting the chromosomal segregation machinery indirectly by associating with specific or nonspecific chromosomal sites. It has been therefore suggested that the segregation of 2m, and hence its overcoming of MIB, likely requires host (non-plasmid-encoded) genes (18). One candidate is the product of the SHF1 (CST6) gene, which has been shown to bind to STB in vivo and in vitro (51).Nucleosomes regulate and modify the ability of proteins to interact with DNA, and the remodeling of chromatin and repositioning of nucleosomes is important in gene regulation and other functions of DNA. There is evidence that specific chromatin structures are...

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Condensed tannins (CTs) form insoluble complexes with proteins and are able to protect them from degradation, which could lead to rumen bypass proteins. Depending on their degrees of polymerization (DP) and molecular weights, CT fractions vary in their capability to bind proteins. In this study, purified condensed tannins (CTs) from a Leucaena leucocephala hybrid were fractionated into five different molecular weight fractions. The structures of the CT fractions were investigated using 13 C-NMR. The DP of the CT fractions were determined using a modified vanillin assay and their molecular weights were determined using Q-TOF LC-MS. The protein-binding affinities of the respective CT fractions were determined using a protein precipitation assay. The DP of the five CT fractions (fractions F1-F5) measured by the vanillin assay in acetic acid ranged from 4.86 to 1.56. The

The existence of multiple-antibiotic-resistant strains of environmental bacteria is commonly linked to human activities. However, multiple-antibiotic-resistant strains of bacteria are also widely found in the Antarctic that has limited human activity. This study was conducted to examine the prevalence of antibiotic-resistant strains among Antarctic bacteria. Forty-five bacterial strains from Estrellas lake of King George Island and Crater lake of Deception Island, Antarctic, were exposed to 30 different antibiotics. Forty out of the 45 bacterial strains were affiliated to 12 genera, Aeromicrobium, Arthrobacter, Bacillus, Brevundimonas, Cryobacterium, Dyadobacter, Flavobacterium, Methylibium, Pedobacter, Pseudomonas, Rhodococcus, and Sphingomonas. Among the bacteria, 43 strains were resistant to at least three antibiotics, and 26 strains were resistant to 10 or more different antibiotics. Pseudomonas spp. and four unknown Microbacteriaceae bacteria were found to be resistant to majority of the antibiotics tested. Two bacteria, each from Estrellas and Crater lakes, were sensitive to all the antibiotics tested. These results indicated that Antarctic bacteria are probably the reservoirs for antibiotic resistance genes.