John Pehrson - Academia.edu (original) (raw)

Papers by John Pehrson

Proteins, Jul 1, 1995

Histone macroH2A has a novel hybrid structure consisting of a large nonhistone region and a regio... more Histone macroH2A has a novel hybrid structure consisting of a large nonhistone region and a region that closely resembles a full‐length histone H2A. One key to understanding macroH2A function is determining the structure and function of its nonhistone region. The nonhistone region of one of the two known macroH2A subtypes was expressed in Escherichia coli and purified using affinity and molecular sieve chromatography. Crystals of the protein suitable for structural studies were grown from polyethylene glycol solutions by vapor equilibration techniques. The crystals belong to the hexagonal space group P64 (or its enantiomorph P62) with unit cell parameters: a = b = 106.2 Å, c = 125.9 Å, α = β = 90°, and γ = 120°. There are four molecules in the asymmetric unit. Self‐rotation function studies revealed three twofold noncrystallographic rotation axes related approximately by 222 symmetry. These crystals have 47% solvent content and diffract to 3.8 Å resolution. © 1995 Wiley‐Liss, Inc.

Molecular and Cellular Biology, 2007

Journal of Biological Chemistry, 1995

This is an Open Access article under the CC BY license.

Molecular and Cellular Biology, 2008

Methods in Enzymology, 2003

Science, 1992

A histone, macroH2A, nearly three times the size of conventional H2A histone, was found in rat li... more A histone, macroH2A, nearly three times the size of conventional H2A histone, was found in rat liver nucleosomes. Its N-terminal third is 64 percent identical to a full-length mouse H2A. However, it also contains a large nonhistone region. This region has a segment that resembles a leucine zipper, a structure known to be involved in dimerization of some transcription factors. Nucleosomes containing macroH2A may have novel functions, possibly involving interactions with other nuclear proteins.

New Comprehensive Biochemistry, 2004

J. Zlatanova and SH Leuba (Eds.) Chromatin Structure and Dynamics: State-of-the-An C. 2004 Elsevi... more J. Zlatanova and SH Leuba (Eds.) Chromatin Structure and Dynamics: State-of-the-An C. 2004 Elsevier BV All rights reserved DOI ... Thus, the location of the centromere, and CENP-A, could be propagated by an epigenetic mark established by nucleoprotein complexes that ...

Nucleic Acids Research, 1992

We have assessed the effects of DNA curvature on pyrimidine dimer (PD) formation by examining the... more We have assessed the effects of DNA curvature on pyrimidine dimer (PD) formation by examining the pattern of PD formation in DNA held in a loop by lambda repressor. The loop region was composed of diverse DNA sequences such that potential PD sites occurred throughout the loop. PD formation in the loop occurred with peaks at approximately 10 base intervals, just 3' of where the bending of the DNA was inferred to be toward the major groove. This relationship between the peaks and the DNA curvature is essentially identical to that observed in the nucleosome. This indicates that DNA curvature is the major source of the periodicity of PD formation in the nucleosome, and supports an earlier model of the conformation of nucleosomal DNA based on PD formation. DNA loops containing diverse sequences should be of general value for assessing the effects of DNA curvature on DNA modification by other agents used to probe DNA-protein interactions and DNA conformation.

Nature Communications, 2013

An image in Supplementary Fig. S9b in this Article, reporting aH3K27me3/DAPI immunofluorescence i... more An image in Supplementary Fig. S9b in this Article, reporting aH3K27me3/DAPI immunofluorescence in iPS cells from the 'dKO' group, was inadvertently duplicated from the 'wt' group. The correct version of the figure appears below.

Methods, 1999

The photoinduced dimerization of adjacent pyrimidines in DNA is influenced in predictable ways by... more The photoinduced dimerization of adjacent pyrimidines in DNA is influenced in predictable ways by DNA conformation. A method is described for determining patterns of pyrimidine dimer formation under conditions in which the chromatin is minimally perturbed. The relation of such patterns to the conformation of nucleosomal core DNA and linker DNA, as well as the interaction of histone H1 with nucleosomal DNA, is presented. Such data indicate that sharp bends in the path of DNA seen in crystals of isolated nucleosome core particles are also present in intact chromatin. They also indicate that most of the linker has very little curvature except for a small bend at its junction with the nucleosome core. The linker path inferred from such experiments supports models in which the chromatin fiber consists of a zigzag chain of nucleosomes.

Journal of Cellular Biochemistry, 1997

MacroH2A is a novel nucleosomal core histone that contains a large nonhistone region and a region... more MacroH2A is a novel nucleosomal core histone that contains a large nonhistone region and a region that closely resembles a full length histone H2A. We have cloned a cDNA that contains the entire coding region of macroH2A1.2, one of the two identified subtypes of macroH2A1. MacroH2A1.2 was found to differ from the other known subtype, macroH2A1.1, in a single segment of the nonhistone region. MacroH2A1 specific antibodies revealed relatively high levels of both subtypes in adult liver and kidney. MacroH2A1.1 was much lower in fetal liver and kidney in comparison to their adult counterparts, and was not detected in adult thymus and testis, tissues with active cell division and differentiation. Both subtypes were present at very low levels or absent from mouse embryonic stem cells maintained in an undifferentiated state by growth in the presence of leukemia inhibitory factor. MacroH2A1.2 increased when the embryonic stem cells were induced to differentiate in vitro, while macroH2A1.1 remained undetectable. These results support the idea that macroH2A1.1 and macroH2A1.2 are functionally distinct, and suggest that changes in their expression may play a role in developmentally regulated changes in chromatin structure and function.

Experimental Cell Research, 2000

The pairing of sex chromosomes during meiosis in male mammals is associated with ongoing heteroch... more The pairing of sex chromosomes during meiosis in male mammals is associated with ongoing heterochromatinization and X inactivation. This process occurs in a specific area of the nucleus that can be discerned morphologically: the sex vesicle or XY-body. In contrast to X inactivation in the somatic cells of female mammals the reasons for X inactivation in the male germline remain obscure. We have recently demonstrated that the inactive X chromosome in somatic cells of female mammals is marked by a high concentration of histone macroH2A. Here we investigate X inactivation in the meiotic cells of the male germline. We demonstrate here that macroH2A1.2 is present in the nuclei of germ cells starting first with localization that is largely, if not exclusively, to the developing XY-body in early pachytene spermatocytes. Our results suggest that inactivation of sex chromosomes in the male germ cell includes a major alteration of the nucleosomal structure.

Developmental Biology, 1985

... DEVELOPMENTAL BIOLOGY 111, 530-533 (1985) Distribution of Histone H1a among Cells of the Sea ... more ... DEVELOPMENTAL BIOLOGY 111, 530-533 (1985) Distribution of Histone H1a among Cells of the Sea Urchin Embryo JOHN R. PEHRSON AND LEONARD H ... This hypothesis predicts that in the late embryo, Hies and Hia will be abundant in the chromatin of di-viding cells, and ...

Developmental Biology, 1986

We show that in sea urchin embryos, the daughter cells of the small micromeres become part of the... more We show that in sea urchin embryos, the daughter cells of the small micromeres become part of the coelomic sacs, in contrast to the long-held view that these sacs are purely of macromere origin. In addition, after prolonged mitotic quiescence, and following their incorporation into the coelomic sacs, these cells resume dividing, contrary to the previous view that they do not divide. Since coelomic sac cells give rise to much of the adult urchin, our results indicate that the small micromeres are founders of cell lineages involved in the formation of adult tissues. The setting aside of these cells in a nondividing state may be analogous to a phenomenon in Drosophila development, in which primordial imaginal and germ cells divide approximately once after the blastoderm stage and do not resume dividing until the larval stage.

Chromosoma, 2001

MacroH2A1 is a histone variant that is found as a component of the inactive X chromosome where it... more MacroH2A1 is a histone variant that is found as a component of the inactive X chromosome where it is detected as a dense accumulation called a macrochromatin body (MCB). Macrochromatin bodies co-localize with Xist RNA, which is an untranslated RNA that is expressed exclusively from the inactive X chromosome of placental mammals. However, no studies to date have investigated whether Xist RNA expression is necessary or sufficient to cause the formation of MCBs. Here we show that expression of Xist RNA is sufficient to cause the formation of MCBs even when Xist is expressed from an inducible transgene at ectopic autosomal sites. Macrochromatin bodies form at sites of transgenic Xist expression in differentiating mouse ES cell lines and transgenic fibroblasts, but MCBs cannot form in undifferentiated ES cells even after prolonged Xist expression. The kinetics of MCB formation revealed that Xist expression precedes MCB formation and that differentiating ES cells undergo a rapid and synchronous transition that renders them competent to form MCBs. Once MCBs have formed, continued expression of Xist is required for their maintenance. These results show that Xist RNA and macroH2A1 function in a common pathway. Expression of Xist in a permissive nuclear environment is sufficient to initiate a chromatin-remodeling event culminating in the incorporation of macroH2A1. The results also strongly suggest the existence of additional regulatory factors for X inactivation that are regulated developmentally. In addition, we present evidence that macroH2A1 density is not simply a measure of the general degree of DNA compaction.