Project description:The NADPH-cytochrome P450 reductase (CPR) is essential for the functioning of microsomal cytochrome P450 (P450) monoxygenases. The biological functions of the CPR-dependent enzymes in the intestine are not known, despite the vast knowledge available on the biochemical properties of the various oxygenases. A mouse model with intestinal epithelium (IE)-specific Cpr-knockout (IE-Cpr-null) was recently generated in this laboratory (Zhang et al., Drug Metab. Dispos., 37, 651-657, 2009). The IE-Cpr-null mice did not display any obvious abnormalities in growth, development, or reproduction, and their intestines appeared to have a normal structure. Despite the absence of observable phenotypes, we hypothesized that loss of the enterocyte CPR expression will impact homeostasis of endogenous compounds, and expression of genes, that have critical biological function in the small intestine. In the present study, we have performed genomic analyses for enterocytes from IE-Cpr-null mice and their wild-type littermates, using Affymetrix Mouse Expression Set 430A 2.0 GeneChip Arrays. Our aim was to identify small intestinal gene-expression changes, which may shed light on potential biological roles of CPR and CPR-dependent enzymes in the small intestine. Our analysis revealed significant expression increases in P450s, transporters, cholesterol biosynthesis, and (unexpectedly) antigen presentation/processing. Further genomic and biochemical analyses revealed potential mechanisms linking CPR-dependent enzymes and the expression of major histocompatibility complex class II genes in the small intestine.
Project description:The NADPH-cytochrome P450 reductase (CPR) is essential for the functioning of microsomal cytochrome P450 (P450) monoxygenases. The biological functions of the CPR-dependent enzymes in the intestine are not known, despite the vast knowledge available on the biochemical properties of the various oxygenases. A mouse model with intestinal epithelium (IE)-specific Cpr-knockout (IE-Cpr-null) was recently generated in this laboratory (Zhang et al., Drug Metab. Dispos., 37, 651-657, 2009). The IE-Cpr-null mice did not display any obvious abnormalities in growth, development, or reproduction, and their intestines appeared to have a normal structure. Despite the absence of observable phenotypes, we hypothesized that loss of the enterocyte CPR expression will impact homeostasis of endogenous compounds, and expression of genes, that have critical biological function in the small intestine. In the present study, we have performed genomic analyses for enterocytes from IE-Cpr-null mice and their wild-type littermates, using Affymetrix Mouse Expression Set 430A 2.0 GeneChip Arrays. Our aim was to identify small intestinal gene-expression changes, which may shed light on potential biological roles of CPR and CPR-dependent enzymes in the small intestine. Our analysis revealed significant expression increases in P450s, transporters, cholesterol biosynthesis, and (unexpectedly) antigen presentation/processing. Further genomic and biochemical analyses revealed potential mechanisms linking CPR-dependent enzymes and the expression of major histocompatibility complex class II genes in the small intestine. Adult (2.5-3.0 month-old) male IE-Cpr-null and WT litermates were used for all experiments. RNA was collected from eight mice of each genotype and RNA from two mice of the same genotype was pooled prior to hybridization to the microarray to create a total of four samples for each genotype.
Project description:Dosage compensation in mammals involves silencing of one X chromosome in XX females, and requires expression, in cis, of Xist silencing RNA. Using microarray analysis to assay expression of X-linked genes in mouse embryonic stem cells, we show that dosage compensation also involves global up-regulation of expression from the active X in both males and females. Up-regulation is complete (ie. 2-fold) only after 2-3 weeks of differentiation. X-linked gene silencing in female cells occurs on a gene-by-gene basis throughout differentiation and includes a sub-group of genes silenced prior to the onset of differentiation and independently of enhanced Xist expression. Keywords: dosage compensation, gene silencing, Xist RNA, microarray
Project description:Human CMV (hCMV) establishes lifelong infections in most of us, causing developmental defects in human embryos and life-threatening disease in immunocompromised individuals. During productive infection, the viral >230,000-bp dsDNA genome is expressed widely and in a temporal cascade. The hCMV genome does not carry histones when encapsidated but has been proposed to form nucleosomes after release into the host cell nucleus. Here, we present hCMV genome-wide nucleosome occupancy and nascent transcript maps during infection of permissive human primary cells. We show that nucleosomes occupy nuclear viral DNA in a nonrandom and highly predictable fashion. At early times of infection, nucleosomes associate with the hCMV genome largely according to their intrinsic DNA sequence preferences, indicating that initial nucleosome formation is genetically encoded in the virus. However, as infection proceeds to the late phase, nucleosomes redistribute extensively to establish patterns mostly determined by nongenetic factors. We propose that these factors include key regulators of viral gene expression encoded at the hCMV major immediate-early (IE) locus. Indeed, mutant virus genomes defcient for IE1 expression exhibit globally increased nucleosome loads and reduced nucleosome dynamics compared with WT genomes. The temporal nucleosome occupancy differences between IE1-defcient and WT viruses correlate inversely with changes in the pattern of viral nascent and total transcript accumulation. These results provide a framework of spatial and temporal nucleosome organization across the genome of a major human pathogen and suggest that an hCMV major IE protein governs overall viral chromatin structure and function.