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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study examines the regulation of the human PRL (hPRL) gene promoter by intracellular calcium. Deletants of the 5'-flanking region of the hPRL gene and constructs consisting of the thymidine kinase promoter linked to the first or second proximal Pit-1 binding site were fused to the bacterial chloramphenicol acetyl transferase (CAT) reporter gene. With the complete 5-kilobase pair (kbp) hPRL promoter sequence the calcium channel agonist Bay K8644 induced a significant 2-fold increase in CAT reporter gene expression and the antagonist verapamil a 4.5-fold reduction, using GH3 cells cultured in physiological levels of calcium. The transcriptional response to calcium influx was similar with a series of 5'-deleted hPRL-CAT constructs including those that comprised the proximal (up to 740 bp) or distal (-1300- to -1700-bp) sequences alone. When treating cells cultured in low calcium conditions the induction with the hPRL promoter increased to 5-fold on the addition of exogenous calcium and Bay K8644. The pituitary-specific expression of the hPRL gene is conferred by the interaction of the pituitary-specific factor Pit-1 with several binding sites located in the 5'-flanking DNA, of which three are located in the proximal region. This suggested that Pit-1 binding sites may be involved in the calcium response.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1991 Nov
PMID:Pit-1 binding sequences permit calcium regulation of human prolactin gene expression. 177 76

We previously showed that ultraviolet (UV) irradiation of cotransfected plasmid DNA molecules stimulated genetic transformation that depended on intermolecular homologous recombination in Chinese hamster ovary (CHO) cells. Repair-proficient cells and an excision repair complementation class 1 (ERCC1) UV-sensitive DNA repair-deficient mutant responded similarly to UV stimulation in cotransfections with plasmids containing linker insertion-disrupted copies of the herpes simplex virus thymidine kinase (HSV-TK) gene. In this study, we cotransfected homologous DNA molecules containing nonoverlapping deletions of the hamster adenine phosphoribosyltransferase (APRT) gene into APRT-deficient CHO ERCC1 (UVL-10) and ERCC2 (UVL-1) excision-repair mutants and parental repair-proficient CHO cells. UV damage in cotransfected circular plasmid molecules stimulated transformation in repair-proficient cells and an ERCC1 mutant, but not in an ERCC2 mutant. Linearization of plasmids prior to cotransfection greatly enhanced transformation frequencies in all three cell lines, but UV stimulation using linear recombination substrates was no longer evident. Our results suggest (i) that the ERCC1 gene defect in CHO UVL-10 cells does not affect UV stimulation of homology-dependent extra-chromosomal recombination, and (ii) that a CHO cell ERCC2 excision-repair mutant, although recombination proficient, may exhibit altered recombination in response to UV damage.
Mol Carcinog 1991
PMID:Ultraviolet stimulation of intermolecular homologous recombination in Chinese hamster ovary cells. 179 89

Tamoxifen, nafoxidine, and clomiphene (1 x 10(-5) M) cause 5- to 15-fold increases in transient expression of plasmids transfected into rat somatomammotrophic pituitary tumor cell lines. To be effective, the antiestrogen must be present during the calcium phosphate transfection though it does not enhance the nuclear uptake or stability of transfected plasmid. The effect occurs with mammalian (rat growth hormone, mouse metallothionein I) or viral (thymidine kinase, Rous sarcoma virus) promoters and is inhibited by prior exposure of cells to high concentrations of estradiol but not glucocorticoid, progesterone or testosterone. Cis-tamoxifen, a conformation with much lower affinity for the estrogen receptor, has only one-fifth the effect of tamoxifen. Neither estradiol nor diethylstilbestrol have similar effects. Tamoxifen also increases endogenous rat growth hormone mRNA in these pituitary tumor cell lines. Transient expression in a number of other cell lines (JEG-3, COS-7, PC-12) is unaffected by tamoxifen suggesting the effect may be cell-type specific though MCF-7 cells are slightly responsive. The mechanism for the potent stimulation of gene transcription by these agents is not apparent but may be relevant to the mechanism of action of these agents as estrogen antagonists in vivo.
Mol Cell Endocrinol 1991 May
PMID:Antiestrogens stimulate expression of transiently transfected and endogenous genes in rat pituitary tumor cell lines. 181 97

Although many cells anchor surface proteins via moieties that are sensitive to phosphatidylinositol-specific phospholipase C (PI-PLC), the anchor moieties of surface proteins of mouse L929 cells resist PI-PLC. By constructing stable hybrids between L929 and lymphoma cells that express glycolipid-anchored proteins in a PI-PLC-sensitive form, we show that PI-PLC resistance behaves as a recessive trait. Since putative mannolipid precursors of the lipid anchors bear alkali-labile substituents which make them resist PI-PLC, these observations are most simply interpreted by postulating that L929 lacks a critical anchor deacylase. Unlike the L929 cell line, two of its descendants, the LM cell line and its thymidine kinase-negative variant (LM-TK-), do not express glycolipid-anchored proteins on their surface. Moreover, unlike L929 cells, LM-TK- cells rapidly inactivate at least one lipid-anchored enzyme in a compartment sensitive to acidotropic amines and leupeptin. By fusion of LM-TK- cells to mouse Thy-1- lymphoma mutants and monitoring of surface expression of lipid-anchored proteins, we assign LM-TK- to lymphoma mutant complementation group H. This genetic assignment is matched by analysis of mannolipids of L929, LM-TK-, wild-type, and class H lymphoma mutant cells: striking similarities are seen between the two wild-type cells by contrast to the mutants. Since the differences pertain to lipids which have properties consistent with their being anchor precursors, we suggest that LM-TK- has a lesion in the synthesis of anchor precursor mannolipids.
Mol Cell Biol 1991 May
PMID:Anchoring and degradation of glycolipid-anchored membrane proteins by L929 versus by LM-TK- mouse fibroblasts: implications for anchor biosynthesis. 182 59

The levels of insulin-like growth factor II/mannose-6-phosphate (IGF-II/Man-6-P) receptor and the insulin-like growth factor I (IGF-I) receptor were measured in the intestinal epithelium after 50% resection of the small intestine. Controls were either pair-fed to match the reduced food intake of the resected group or fed ad libitum. [125I]IGF-II binding was transiently increased 2-fold in the distal segment of the small intestine 3 days after resection compared with the pair-fed control. Receptor levels increased from 2.60 nmol/mg protein (pair-fed) to 4.63 nmol/mg protein (resected; p less than 0.001) with no significant change in affinity of IGF-II binding (Kd = 11.2 vs. 9.8 nmol/l). The increase in IGF-II/Man-6-P receptors coincided with increased activity of thymidine kinase in the distal intestinal segment after the resection. [125I]IGF-I binding remained unchanged after the resection. However, the decreased food intake of the pair-fed and resected groups caused a 2-fold increase in the amount of IGF-I receptors (0.18 nmol/mg protein; p less than 0.001) compared with the control fed ad libitum (0.08 nmol/mg protein). IGF-II/Man-6-P receptors were only moderately increased during restricted food intake (2.60 vs. 1.78 nmol/mg protein; p less than 0.005). These results suggest that the IGF-II/Man-6-P receptor may play a role in the adaptive regenerative response of the intestinal epithelium.
Mol Cell Endocrinol 1991 Mar
PMID:Insulin-like growth factor II/mannose-6-phosphate receptors are transiently increased in the rat distal intestinal epithelium after resection. 185 Nov 13

The cycloburtane nucleoside analog (1R-1 alpha,2 beta,3 alpha)-9-[2,3-bis(hydroxymethyl)cyclobutyl]guanine [(R)-BHCG or SQ 34,514] was recently synthesized and shown to be the active enantiomer of (+/-)-BHCG (SQ 33,054), a potent inhibitor of several strains of herpesviruses [J. Med. Chem 34:1415-1421 (1991); Antiviral Res. 13:41-52 (1990)]. In plaque reduction assays, (R)-BHCG was about 1000 times more active than its S-enantiomer on herpes simplex virus type I (HSV-1) and over 200 times more active against a thymidine kinase-deficient mutant HSV-1 and human cytomegalovirus (HCMV). We now show that both (R)-BHCG and (S)-BHCG are efficiently phosphorylated to their mono-, di-, and triphosphates by HSV-1-infected cells, in a manner similar to that of acyclovir [Proc. Natl. Acad. Sci. USA 74:5716-5720 (1977)]. The uptake of both enantiomers was greatly increased upon infection; however, (S)-BHCG was taken up to about twice the extent of (R)-BHCG and accumulated primarily as the mono- and diphosphates. (R)-BHCG accumulated primarily as the triphosphate, and accumulation was linear with both time and added drug concentration. The triphosphate had an apparent half-life of about 10 hr. Metabolic studies using HCMV-infected cells showed only a small degree of phosphorylation of (R)-BHCG and none of (S)-BHCG. When cells were labeled with 25 microM (R)-BHCG, the amount of (R)-BHCG triphosphate formed was less than 0.5 pmol/10(6) cells. Interestingly, the ED50 value of (R)-BHCG is about 100-fold higher against HCMV than against HSV-1, and the relative levels of (R)-BHCG triphosphate formed in cells infected by the two viruses are roughly proportional to the antiviral activities.
Mol Pharmacol 1991 Sep
PMID:Selective activity and cellular pharmacology of (1R-1 alpha,2 beta,3 alpha)-9-[2,3-bis(hydroxymethyl)cyclobutyl]guanine in herpesvirus-infected cells. 189 29

The cytotoxic and genotoxic effects of glutaraldehyde were studied in vitro in the human TK6 lymphoblast cell line and in primary cultures of rat hepatocytes. TK6 lymphoblasts were exposed to glutaraldehyde for 2 hr in serum-free GSH-free media. Cytotoxic effects were observed at concentrations as low as 10 microM with only 10% cell survival at 20 microM. Alkaline elution studies indicated that glutaraldehyde-induced DNA-protein crosslinking increased linearly over the concentration range from 0 to 25 microM. Glutaraldehyde-induced mutations were assessed at the thymidine kinase locus over the same concentration range and reached a plateau at 10 microM of about six times the background mutant frequency. At equivalent levels of DNA-protein crosslinks and cytolethality, glutaraldehyde was mutagenic at approximately a one-seventh lower concentration than the rodent nasal carcinogen formaldehyde (Craft et al.; Mutation Research 176:147-155, 1987). Glutaraldehyde induced a marginal increase in unscheduled DNA synthesis in the in vitro hepatocyte DNA repair assay, but only at the two highest concentrations of 50 and 100 microM, indicating the induction of some DNA excision-repair activity. These data demonstrate that glutaraldehyde exhibits DNA-reactive genotoxic activity that may involve, at least in part, DNA-protein crosslinking in these cell culture models. These findings suggest the need to examine the potential carcinogenic activity of glutaraldehyde in appropriate inhalation studies.
Environ Mol Mutagen 1991
PMID:Evaluation of the genotoxic potential of glutaraldehyde. 190 74

Two genetics markers: the herpes simplex virus thymidine kinase and Escherichia coli beta-galactosidase genes were inserted into the 36K protein gene of vaccinia virus located in a HindIII-P DNA fragment. An unstability of recombinant viruses with Lac(+)-phenotype were discovered. A mechanism of viruses unstable variants formation was proposed, it was confirmed by the results of hybridisation analyses of virus recombinant genomes. The importance of a late nonstructural 36K protein gene for virus reproduction was demonstrated.
Mol Biol (Mosk)
PMID:[Molecular biological study of the vaccinia virus genome. IV. The late nonstructural 36K protein of vaccinia virus is vitally important]. 190 41

The nuclear proto-oncogene c-myb is preferentially expressed in lymphohematopoietic cells, in which it plays an important role in the processes of differentiation and proliferation. The mechanism(s) that regulates c-myb expression is not fully understood, although in mouse cells a regulatory mechanism involves a transcriptional block in the first intron. To analyze the contribution of the 5' flanking sequences in regulating the expression of the human c-myb gene, we isolated a genomic clone containing extensive 5' flanking sequences, the first exon, and a large portion of the first intron. Sequence analysis of a subcloned 1.3-kb BamHI insert corresponding to 687 nucleotides of the 5' flanking sequence, the entire first exon, and 300 nucleotides of the first intron revealed the presence of closely spaced putative Myb binding sites within a segment extending from nucleotides -616 to -575 upstream from the cap site. A 165-bp segment containing these putative Myb binding sites was linked to a human thymidine kinase (TK) cDNA driven by a low-activity proliferating cell nuclear antigen promoter and cotransfected into TK- ts13 cells with a plasmid in which a full-length human c-myb cDNA is driven by the early simian virus 40 promoter; Myb inducibility of TK mRNA expression was observed both in transient expression assays and in stable transformants. The highest level of inducibility was detected when the 165-bp fragment was placed 138 bp upstream of the proliferating cell nuclear antigen promoter-TK cDNA reporter unit or 3' of the TK cDNA. Mutation of the putative Myb binding sites greatly reduced c-myb transactivation of TK mRNA expression and specifically reduced the binding of in vitro-translated Myb protein at those sites. Finally, c-myb transactivated TK mRNA expression driven by a segment of the authentic c-myb 5' flanking region containing the Myb binding sites. These data suggest that human c-myb maintains high levels of Myb protein in cells that require this gene product for proliferation and/or differentiation by an autoregulatory mechanism involving Myb binding sites in the 5' flanking region.
Mol Cell Biol 1991 Dec
PMID:Positive autoregulation of c-myb expression via Myb binding sites in the 5' flanking region of the human c-myb gene. 194 82

The influence on homologous and heterologous promoter activity of DNA extending 2.4 kb upstream of the human renin gene (REN) was examined by transient expression assay in JEG-3 cells, using the gene for chloramphenicol acetyl transferase (CAT) as reporter, and cotransfection with pCH110 to control for transfection efficiency. Analyses of constituent subfragments of the region 5' of residue -144, using the herpes simplex virus thymidine kinase (tk) promoter to drive transcription, provided no evidence for negative regulatory influences within the -2400 to -144 DNA. That distal 5'-flanking DNA may have little influence on promoter activity is further supported by a sharp decline in nucleotide homology between human, rat and mouse renin genes further upstream than human residue -604. Constructs containing renin DNA to residue +13, i.e., which retained the REN promoter, all displayed very low CAT activities, consistent with negative cis-acting control within the -149 to +13 region. This finding contrasts with results of similar studies for mouse, in which renin gene control was suggested to be mediated primarily via cell-specific trans-acting activator(s) acting on yet-to-be identified enhancer(s). Mouse renin genes have, however, a common DNA insertion that could have disrupted the negative element in this region, and which might contain enhancer target(s) for trans-acting factor(s). In conclusion, the present study involving JEG-3 cells has demonstrated that distal human renin 5'-flanking DNA has little cis-acting influence on promoter activity, whereas DNA located within 100 base pairs of the renin promoter may have a negative regulatory effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1991 Sep
PMID:Transient expression analyses of DNA extending 2.4 kb upstream of the human renin gene. 195 73


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