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D I Linzer

Publications and source records attributed to D I Linzer.

At least 55 records · Page 3Linked to original sources
PubMed1992

Placental-specific expression from the mouse placental lactogen II gene promoter.

The gene for mouse placental lactogen II (mPL-II) has been isolated and characterized. This gene contains five exons, with a transcription start site 59 nucleotides upstream of the translation initiation ATG. Introduction of a DNA construct containing 2.7 kilobases of sequence upstream of the mPL-II transcription initiation site directed the synthesis of a linked coding region for the simian virus 40 large and small tumor antigens in placental trophoblast giant cells of transgenic mice. The pattern of simian virus 40 transgene expression in the placenta was indistinguishable from that of the endogenous mPL-II gene. In contrast, the first 569 base pairs upstream of the transcription start site proved insufficient to direct placental expression. Thus, one or more elements required for placental trophoblast giant cell expression have been localized to a region between -2700 and -569 of the mPL-II gene.

Amino Acid Sequence↗
PubMed1991

Localization of placental lactogen-I in trophoblast giant cells of the mouse placenta.

The purpose of this investigation was to identify the cellular origin of placental lactogen-I (PL-I) expression in the mouse placenta and to cytologically define the transition from PL-I to PL-II expression during gestation. PL-I mRNA expression was assessed by in situ hybridization, and expression of PL-I and PL-II protein was determined by immunocytochemical analysis. PL-I mRNA and protein were localized to trophoblast giant cells. Trophoblast giant cells ceased producing PL-I at midgestation and began expressing PL-II. PL-I immunoreactivity was present in trophoblast giant cells on Days 9 and 10 of gestation but was not detectable in trophoblast giant cells on Day 11 of gestation. Immunoreactive PL-II-producing giant cells were detected first on Day 10 of gestation, continuing on Day 11 of gestation. Expression of PL-I and PL-II signals a significant functional transition in trophoblast giant cells of the developing mouse placenta.

Animals↗
PubMed1990

A cloned human CCAAT-box-binding factor stimulates transcription from the human hsp70 promoter.

The basal promoter of the human hsp70 gene is predominantly controlled by a CCAAT element at position -70 relative to the transcriptional initiation site. We report the isolation of a novel cDNA clone encoding a 114-kDa polypeptide that binds to the CCAAT element of the hsp70 promoter. Expression of this CCAAT-binding factor (CBF) cDNA activated transcription from cotransfected hsp70 promoter-reporter gene constructs in a CCAAT-dependent manner. CCAAT-binding factor shows no homology to the previously identified human CCAAT transcription factor or rat CCAAT/enhancer-binding protein.

Amino Acid Sequence↗
PubMed1989

Co-localization of elements required for phorbol ester stimulation and glucocorticoid repression of proliferin gene expression.

Proliferin (PLF) gene expression provides a model of growth-related transcriptional activation in mouse cells. Transcription from a cloned PLF promoter is inducible by phorbol esters, and this induction involves a region of 31 bp that includes an AP-1 site and a cluster of sites similar to the simian virus 40 (SV40) SphI element. The mutation of either the AP-1 or the SphI sites abolishes phorbol ester induction, and the transfer of this 31-bp sequence to a site upstream of a minimal promoter is sufficient to confer phorbol-ester responsiveness. In contrast to phorbol esters, glucocorticoids repress PLF transcription, which results in a reduced accumulation of PLF mRNA in serum-stimulated cells. Repression is dependent on the glucocorticoid receptor, which binds to the PLF promoter in a region that includes the AP-1 site, and the 31-bp phorbol ester 12-O-tetra decanoylphorbol-13-acetate (TPA)-inducible region is sufficient to mediate glucocorticoid repression. In addition, extracts from glucocorticoid-treated and untreated mouse cells are found to differ in the nature of the protein complexes that interact with the AP-1 site.

Animals↗
PubMed1989

Participation of multiple factors, including proliferin, in the inhibition of myogenic differentiation.

Proliferin (PLF) is a secreted glycoprotein in the prolactin-growth hormone family in mice. PLF expression was detected in C3H 10T1/2 fibroblasts, but not in two 10T1/2-derived myogenic cell lines, and was restored in two nondifferentiating variants of one of these myogenic cell lines. Transient expression of one form of PLF (PLF1) inhibited expression from a muscle-specific gene promoter; a second form of PLF, which differed at three amino acid residues, displayed no activity in this transient assay. Introduction of a PLF1 expression construct into both muscle- and 10T1/2-derived myoblasts resulted in cell lines that were no longer myogenic or that differentiated only partially. Analysis of these cell lines revealed that differentiation could be obstructed at several steps and by one or more factors in addition to PLF. Although expected to function in vivo as an extracellular hormone, PLF did not appear to be acting through a cell surface receptor to inhibit differentiation in these cultured myoblasts.

Animals↗
PubMed1989

Mouse placental lactogen-I: RIA and gestational profile in maternal serum.

A RIA for mouse placental lactogen-I (mPL-I) was developed using recombinant mPL-I as the standard, radioligand, and antigen for antiserum production. Displacement curves for dilutions of serum and placental extracts from pregnant mice were parallel to the recombinant mPL-I standard curve. Serum from male and nonpregnant female mice and high concentrations of mouse PRL, GH, PL-II, proliferin, and proliferin-related protein did not cross-react in the assay. mPL-I appeared in maternal serum on day 6 of pregnancy. Its concentration remained low until day 8 and them increased to a very large peak on days 9-11 (maximum concentration, approximately 8 micrograms/ml). The mPL-I concentration declined after day 11, but the hormone could be detected at low concentration in maternal serum until the end of pregnancy. On day 10 of pregnancy, the mPL-I concentration of maternal serum was correlated with litter size. Fractionation of serum from 10-day pregnant mice by size exclusion chromatography indicated the absence of high mol wt forms of mPL-I in the circulation.

Animals↗
PubMed1989

Mutational analysis of a lactogenic hormone reveals a role for lactogen-specific amino acid residues in receptor binding and mitogenic activity.

Mutant forms of mouse placental lactogen-II (PL-II) have been generated to assess the role of specific amino acid residues and protein regions in binding to the PRL receptor and in mitogenic activity. Conversion of any of three lactogen-specific residues significantly reduced both of these hormone functions; mutation of the two other lactogen-specific amino acids revealed only minimal effects unless these changes were coupled with a second mutation. Deletions within the PL-II protein all resulted in a complete loss of function, but switching regions between PL-II and proliferin, another member of the prolactin family in the mouse, did yield a chimeric protein with some PRL-like activity. This activity was increased substantially by conversion of one amino acid residue in the proliferin region to the corresponding lactogen-specific residue. The locations of the amino acids that have been found to affect hormone function are predicted to be closely apposed in the folded protein, suggesting that this region may be the site of interaction of this lactogenic hormone with the PRL receptor.

Amino Acid Sequence↗
PubMed1989

Expression of multiple forms of the prolactin receptor in mouse liver.

We have characterized the PRL receptor (PRL-R) present in mouse liver by purification, cross-linking, and immunological analysis of the protein, and by the isolation of PRL-R cDNA clones. Analysis of the cDNA clones indicates that the liver receptor is actually a family of proteins. Two of these proteins are predicted to be synthesized as precursors of 303 and 292 amino acids, with common signal sequences, extracellular domains, and transmembrane domains; a portion of their cytoplasmic domains are also identical, but these proteins differ markedly in the terminal region of this domain. A third PRL-R protein is predicted to be a truncated form and may be secreted. These multiple PRL-R mRNAs appear to be encoded by at least two genes, with the sequence variation for the two full-length proteins likely due to alternative RNA splicing. These results suggest that the varied actions of PRL may involve multiple receptors that are part of distinct signal transduction pathways.

Amino Acid Sequence↗
PubMed1989

A mutant lactogenic hormone binds, but does not activate, the prolactin receptor.

We have generated mutations in mouse placental lactogen II, a hormone in the PRL/GH family that binds to the PRL receptor, to investigate the role of the conserved cysteine residues in hormone function. Disruption of the small C-terminal disulfide loop did not significantly alter hormone activity. Substitution of serine for cysteine-51, which prevents formation of the large disulfide loop, results in a protein equivalent to placental lactogen II in receptor-binding activity; however, this mutant protein is not mitogenic in an assay for lactogenic hormones. These results indicate that PRL receptor occupancy and activation are distinct events.

Animals↗
PubMed1988

Detection of two growth hormone receptor mRNAs and primary translation products in the mouse.

Two mouse growth hormone-receptor primary translation products of Mr 95,900 and 31,800 were identified from in vitro-translated late pregnant mouse liver mRNA. RNA isolated from mouse liver was translated in a rabbit reticulocyte lysate system containing [35S]methionine, and the growth hormone receptor primary translation products were identified by immunoprecipitation with anti-mouse growth hormone receptor antiserum followed by sodium dodecyl sulfate/PAGE and fluorography. Detectable amounts of the Mr 95,900 and 31,800 proteins were not present in in vitro-translated nonpregnant mouse liver mRNA. This result is consistent with previous observations of the up-regulation of growth hormone receptors in the liver during pregnancy in the mouse. Northern (RNA) blot analysis of mouse liver and adipose tissue RNA with a rabbit growth hormone receptor cDNA probe revealed two hybridizing mRNAs of approximately 3.9 and 1.2 kilobases. These two RNAs were greatly up-regulated in liver, but not in adipose tissue, during pregnancy. The sizes of these mRNAs closely matched predictions of the sizes of the mRNAs coding for the proteins of Mr 95,900 and 31,800 made by in vitro translation of size-fractionated late-pregnant mouse liver poly(A)+RNA. These results suggest a mechanism for the generation of both the heterogeneous forms of the growth hormone receptor identified in mouse liver membrane preparations and the mouse serum growth hormone-binding protein.

Animals↗
PubMed1988

Trophoblastic giant cells of the mouse placenta as the site of proliferin synthesis.

Proliferin (PLF) is a PRL-related glycoprotein secreted by a number of mouse cell lines and by minced mouse placenta. To further investigate the hormone-like characteristics of PLF, we have determined the site of PLF synthesis and storage in the placenta and its concentration in blood serum during pregnancy. By immunohistochemical staining and in situ hybridization PLF protein and messenger RNA (mRNA) were localized to the trophoblastic giant cells. Individual cells contained both PLF and placental lactogen II. Trophoblastic giant cells appear to secrete PLF into the circulation since PLF was found at levels up to 5 micrograms/ml in the serum of pregnant mice by RIA and at somewhat lower concentrations in the amniotic fluid. Moreover, the serum concentration of PLF during pregnancy varied directly with the level of PLF mRNA in the placenta and with the number of placentas per animal. These findings are consistent with the hypothesis that PLF is a placental hormone; its function is not known.

Animals↗
PubMed1988

Chromosomal mapping of the prolactin/growth hormone gene family in the mouse.

The chromosomal assignments of genes in the PRL/GH family in the mouse have been determine in mouse-hamster hybrid cell lines. Mouse GH (mGH) appears to be encoded by a single copy gene located on chromosome 11 and is part of a highly conserved region between mouse chromosome 11 and human chromosome 17. All of the other genes in this hormone family, including those encoding mPRL, mouse placental lactogens I and II, and mouse proliferin and proliferin-related protein, map to chromosome 13.

Animals↗
PubMed1988

Biological, immunological, and binding properties of recombinant mouse placental lactogen-I.

Mouse placental lactogen-I (mPL-I) cDNA was inserted into a eukaryotic expression vector and introduced into Chinese hamster ovary cells. Cell lines that secrete high concentrations of mPL-I were isolated, and this glycoprotein was purified from the cell culture-conditioned medium. Recombinant mPL-I (mPL-Ir) is very similar to placental mPL-I (mPL-Ip) in its recognition by polyclonal antisera raised against either mPL-Ip or mPL-Ir, in displacing [125I]iodo-mPL-II from binding sites on mouse liver microsomal membranes, and in stimulating the synthesis of alpha-lactalbumin in primary cultures of mouse mammary epithelial cells. Structural comparison of mPL-Ir and mPL-Ip by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that mPL-Ir comprises several proteins with mol wt ranging from 34.5-38K, while mPL-Ip consists of a similar set of proteins with mol wt ranging from 36.5-42K. Treatment of the two proteins with neuraminidase resulted in similar 2-4K decreases in mol wt. Treatment of mPL-Ip with peptide:N-glycosidase-F to remove asparagine-linked oligosaccharide chains resulted in the formation of 28K and 29K mol wt species, while treatment of mPL-Ir with the same enzyme yielded 28K and 28.5K mol wt products.

Animals↗
PubMed1988

Characterization of proliferin-related protein.

Proliferin-related protein (mPRP) is a member of the PRL/GH family in the mouse. We have generated an antiserum against mPRP expressed as a bacterial fusion protein; this antiserum detects mPRP in the conditioned media of placental tissue cultures as a heterogeneous population of glycoproteins. We have also expressed mPRP in mammalian tissue culture cells and purified the secreted protein. N-terminal sequence analysis of the purified protein reveals that it is secreted as a 214 amino acid protein after removal of a 30 amino acid signal polypeptide. An antiserum raised against the purified protein detects high levels of mPRP in maternal serum during gestation. The site of synthesis of this protein has been localized by in situ hybridization to the basal zone of the day-10 mouse placenta, which is distinct from the site of synthesis of other placental proteins in this family.

Amino Acid Sequence↗
PubMed1988

Autocrine stimulation of Nb2 cell proliferation by secreted, but not intracellular, prolactin.

We have introduced expression constructs for mouse PRL (mPRL) or a nonsecreted form of mPRL into the PRL-responsive Nb2 rat lymphoma cell line. Cell lines resulting from transfection of Nb2 cells with the wild type mPRL construct synthesize and secrete mPRL. These cells are able to grow independently of added lactogens, and conditioned media and cell extracts from these cultures stimulate the growth of Nb2 cells. In contrast, cells synthesizing the nonsecreted mPRL do not proliferate in the absence of added lactogenic hormones, and conditioned media from these cell cultures do not have PRL-like activity in the Nb2 cell growth assay. PRL protein is detected in these nonsecreting cell lines; however, extracts from these lines are generally unable to stimulate Nb2 cell proliferation. These results indicate that cells can respond in an autocrine fashion to PRL, but that an intracellular form of PRL is unable to activate Nb2 cell growth.

Animals↗
PubMed1987

A growth-related mRNA in cultured mouse cells encodes a placental calcium binding protein.

We have characterized an mRNA that increases in abundance after serum stimulation of quiescent mouse fibroblasts. This mRNA, designated 18A2, encodes a predicted polypeptide of 101 amino acids with homology to known calcium binding proteins. A variety of mouse tissues express the 18A2 mRNA, with the highest levels detected in the non-pregnant uterus and in the placenta. The concentration of 18A2 mRNA in total placental RNA decreases from day 8 to day 10 of pregnancy, and is below detection throughout the latter half of gestation. In serum-stimulated fibroblasts, the increase in 18A2 mRNA is dependent on protein synthesis. The 18A2 mRNA is similar in size, serum-inducibility, and sequence to the 2A9 mRNA (1), but these mRNAs are derived from distinct genes. This suggests that the mouse genome harbors a family of serum-inducible genes encoding proteins predicted to bind calcium.

Animals↗