The nucleosomal repeat lengths of bulk chromatin and the chromatin of transcriptionally active and inactive genes were analyzed in two mouse cell lines and adult mouse spleens. The adult beta-globin gene exhibits a nucleosomal repeat length approximately 11 base pairs longer than (i) an inactive embryonic globin gene, epsilon y3; (ii) an immunoglobulin heavy chain gene, Cmu; and (iii) the bulk ...

Communication between distantly spaced genomic regions is one of the key features of gene regulation in eukaryotes. Chromatin per se can stimulate efficient enhancer-promoter communication (EPC); however, the role of chromatin structure and dynamics in this process remains poorly understood. Here we show that nucleosome spacing and the presence of nucleosome-free DNA regions can modulate chroma...

The diameters of chromatin fibers from Thyone briareus (sea cucumber) sperm (DNA linker length, n = 87 bp) and Necturus maculosus (mudpuppy) erythrocytes (n = 48 bp) were investigated. Soluble fibers were frozen into vitrified aqueous solutions of physiological ionic strength (124 mM), imaged by cryo-EM, and measured interactively using quantitative computer image-processing techniques. Frozen-...

Effects of calyculin A, a potent inhibitor of protein phosphatases 1 and 2A, on X-ray cell killing and chromatin structure were studied using cultured mammalian cells (BHK21). Calyculin A at concentrations of 2.5-20 nM enhanced X-ray cell killing when exponentially growing BHK21 cells were treated with calyculin A for 30 min after X-irradiation. A 30-min treatment with this drug induced chromat...

We have examined the chromatin structure of the centromere regions of chromosomes III and XI in yeast by using cloned functional centromere DNAs (CEN3 and CEN11) as labeled probes. When chromatin from isolated nuclei is digested with micrococcal nuclease and the resulting DNA fragments separated electrophoretically and blotted to nitrocellulose filters, the centromeric nucleosomal subunits are ...

X-inactivation is the unusual mode of gene regulation by which most genes on one of the two X chromosomes in female mammalian cells are transcriptionally silenced. The underlying mechanism for this widespread transcriptional repression is unknown. This thesis investigates two key aspects of the X-inactivation process. The first aspect is the correlation between chromatin structure and gene expr...

in this study calf thymus chromatin was fractionated into active (s1 and s2) and inactive (p 2) chromatin. then the interaction of an anthracyc1ine antibiotic, adriamycin, with these fractions was investigated employing absorption and difference uv nis spectroscopy and sds and agarose gel electrophoreses. the results suggest that the binding of adriamycin to the s 1 fraction is slight but s2 an...

During meiotic prophase in male mammals, the X and Y chromosomes are incorporated in the XY body. This heterochromatic body is transcriptionally silenced and marked by increased ubiquitination of histone H2A. This led us to investigate the relationship between histone H2A ubiquitination and chromatin silencing in more detail. First, we found that ubiquitinated H2A also marks the silenced X chro...

Rat liver nuclei were fractionated into chromatin and nucleolar fractions. Chromatin DNA, which does not form hybrids with rRNA, was, nevertheless, able to hybridize with 32P-labelled total nucleolar RNA. The optimal temperature for this hybridization was 55 degrees C when the reaction was carried out in 2 X SSC (0.3 MnaCl + 0.3 M-sodium citrate). The hybrids formed were specific, as judged by ...