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G S Robinson

Publications and source records attributed to G S Robinson.

25 records · Page 2Linked to original sources
PubMed1989

A direct role for C/EBP and the AP-I-binding site in gene expression linked to adipocyte differentiation.

Adipocyte differentiation is accompanied by the transcriptional activation of many new genes, including the gene encoding adipocyte P2 (aP2), an intracellular lipid-binding protein. Using specific deletions and point mutations, we have shown that at least two distinct sequence elements in the aP2 promoter contribute to the expression of the chloramphenicol acetyltransferase gene in chimeric constructions transfected into adipose cells. An AP-I site at -120, shown earlier to bind Jun- and Fos-like proteins, serves as a positive regulator of chloramphenicol acetyltransferase gene expression in adipocytes but is specifically silenced by adjacent upstream sequences in preadipocytes. Sequences upstream of the AP-I site at -140 (termed AE-1) can function as an enhancer in both cell types when linked to a viral promoter but can stimulate expression only in fat cells in the intact aP2 promoter. The AE-1 sequence binds an adipocyte protein identical or very closely related to an enhancer-binding protein (C/EBP) that has been previously implicated in the regulation of several liver-specific genes. A functional role for C/EBP in the regulation of the aP2 gene is indicated by the facts that C/EBP mRNA is induced during adipocyte differentiation and the aP2 promoter is transactivated by cotransfection of a C/EBP expression vector into preadipose cells. These results indicate that sequences that bind C/EBP and the Fos-Jun complex play major roles in the expression of the aP2 gene during adipocyte differentiation and demonstrate that C/EBP can directly regulate cellular gene expression.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Characterization and hepatic expression of rat alpha 1-inhibitor III mRNA.

A 2.5-kilobase cDNA clone (AF7), encoding 785 amino acids, was isolated from a rat liver cDNA library constructed in the expression vector lambda gt11. M13 vector sequence analysis yielded a deduced protein primary structure that was 89% homologous to the prototype alpha 1-inhibitor III (alpha 1I3) sequence presented in the preceding paper by Braciak et al. (Braciak, T. A., Northemann, W., Hudson, G. O., Shields, B. R., Gehring, M. R., and Fey, G. H. (1988) J. Biol. Chem. 263, 3999-4012) with regard to exact matches and 92% homologous when considering chemically conserved residues. The clone also possessed 100% homology to the putative bait region of a variant clone (pRLA1I3/27J) of alpha 1I3. Such sequence data demonstrates that the AF7 clone corresponds to a member of the family of variant alpha 1I3 mRNAs. Furthermore, this report presents the entire mRNA sequence corresponding to the 3'-half of alpha 1I3 variant 27J. We have utilized AF7 cDNA to study the expression of alpha 1I3 messenger RNA encoding this liver-specific glycoprotein under conditions known to alter hepatic gene expression. Our data reveal that alpha 1I3 mRNA expression is not only regulated during the acute-phase response but is also modulated in response to a variety of changing physiological conditions, most notably liver development. Steady state levels of mRNA were quantified using Northern blot techniques and laser densitometry. During acute phase response initiated by turpentine injection, the relative abundance of alpha 1I3 mRNA decreased 4-5-fold over a period of 24 h. Following partial hepatectomy, the regenerating liver expressed six-fold less alpha 1I3 mRNA than untreated liver after 24 h. This reduced level was maintained over a 2-day period. We have also demonstrated that alpha 1I3 mRNA expression is developmentally regulated. Fetal rat liver did not contain detectable concentrations of rat alpha 1I3 mRNA even as late as 4 days prior to birth. However, trace amounts were observed from birth until approximately 20 days of age when alpha 1I3 mRNA levels increased 10-fold to maximal adult quantities over the following 2 or 3 weeks. During the course of pregnancy, alpha 1I3 mRNA remained essentially constant until approximately 4 days prior to birth when a precipitous decline to 40% of the original level was noted. Subsequently, normal values were gradually restored over a 30-day postpartum period.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute-Phase Proteins↗
PubMed1988

Cell-cell and cell-matrix interactions differentially regulate the expression of hepatic and cytoskeletal genes in primary cultures of rat hepatocytes.

Freshly isolated adult rat hepatocytes exhibit a flat, extended morphology when cultured on dried rat tail collagen in the presence of growth factors; they actively synthesize DNA and express high levels of cytoskeletal mRNAs and proteins (actin, tubulin, cytokeratins, vinculin, alpha-actinin, and desmoplakin), while exhibiting low levels of liver-specific mRNAs (albumin, alpha 1-inhibitor III, and alpha 1-antitrypsin) and limited synthesis and secretion of albumin. Hepatocytes cultured on hydrated gel matrix from the Engelbreth-Holm-Swarm (EHS) mouse tumor form small spherical aggregates and exhibit low DNA, cytoskeletal mRNA, and protein synthesis, while at the same time exhibiting elevated liver-specific mRNAs and albumin production; these cells, therefore, more nearly conform to the program of gene expression seen within the normal animal. Hepatocytes on hydrated rat tail collagen resemble those on dry collagen when cultured at low density, but at high density they form compact trabecular aggregates, synthesize negligible amounts of DNA, and maintain a pattern of gene expression resembling that of hepatocytes seeded on the EHS matrix. If cell morphology is compact, as on EHS or on hydrated rat tail collagen when densely populated, DNA synthesis and expression of cytoskeletal genes are low, while liver-specific mRNAs are abundant. When cells are extended the opposite is the case. Without the growth supplement DNA synthesis is low throughout but gene expression is little affected. These studies point to the importance of cell-cell and cell-matrix interactions in determining the differentiated phenotype of hepatocytes, and they reveal an inverse relationship between cytoskeletal and liver-specific protein expression.

Albumins↗
PubMed1984

Differential expression of two neural cell-specific beta-tubulin mRNAs during rat brain development.

We recently demonstrated that beta-tubulin mRNA expression is regulated during rat brain development. This is manifested by a dramatic decrease in both 1.8- and 2.9-kilobase (kb) mRNAs when extensive neurite elongation is occurring. Coincident with these decreases is the increased production of a 2.5-kb mRNA. (J.F. Bond and S.R. Farmer, Mol. Cell. Biol. 3:1333-1342, 1983). In the present study, we have isolated and characterized three different cDNAs corresponding to beta-tubulin mRNAs (R beta T.1, R beta T.2, and R beta T.3). Hybridization of 3' untranslated region subclones of R beta T.1 and R beta T.2 cDNAs to RNA from a variety of rat tissues and cells revealed that these two cDNAs are neural cell specific. R beta T.1 corresponds to an abundant 1.8-kb mRNA expressed only at early stages of rat brain development. R beta T.2 corresponds to the 2.5-kb mRNA expressed at later stages. These data strongly suggest that there is differential expression of the beta-tubulin multigene family during rat brain development.

Aging↗
PubMed1980

Pulmonary embolism during mannitol therapy.

A 25-year-old paraplegic woman suffered cardiopulmonary arrest due to a major pulmonary embolism during intravenous mannitol therapy. Although it is possible that the mannitol caused an acute episode of hemagglutination, we postulate that rapid administration of mannitol caused dilation of her venous system, causing a preexisting clot to break loose.

Adult↗