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D I Linzer

Publications and source records attributed to D I Linzer.

70 records · Page 4Linked to original sources
PubMed1987

Transcriptional regulation of proliferin gene expression in response to serum in transfected mouse cells.

The sequences upstream of a proliferin gene have been isolated, linked to a reporter gene, and transfected into mouse cell cultures. In low serum concentrations, transcription from the transfected DNA is very weak; transcriptional activity is induced 20- to 40-fold in transfected cultures grown in high serum concentrations. Initiation of transcription occurs at the same site in the transfected DNA as in endogenous proliferin genes expressed in placental tissue and in cell cultures. Sequences within 578 nucleotides upstream of this initiation site are sufficient for complete serum-inducible expression, but deletion of the upstream sequences to within 211 nucleotides of the start site abolishes promoter activity. In contrast, the upstream region from a second proliferin gene is only weakly inducible in transfected cell cultures, even though these two promoter regions share 97% nucleotide sequence homology.

Acetyltransferases↗
PubMed1987

Control of proliferin gene expression in serum-stimulated mouse cells.

The serum-inducible expression of proliferin genes in BALB/c 3T3 cells was found to be dependent on both protein synthesis and an extended presence of serum in the medium. Even though no mature proliferin mRNA was detected in serum-starved cells, transcription of the proliferin genes occurred in these resting-cell cultures, indicating that posttranscriptional events may be important for regulating proliferin mRNA levels. These results suggest that protein synthesis after serum stimulation of quiescent mouse fibroblasts is required for posttranscriptional processing or stabilization of proliferin RNA. Proliferin RNA levels were found to be heterogeneous among serum-stimulated cells analyzed by in situ hybridization. This heterogeneity is probably due to asynchrony in the population and may point to a correlation between the time of proliferin expression and the time of entry of a cell into S phase.

Animals↗
PubMed1987

Molecular cloning and expression of mouse placental lactogen I complementary deoxyribonucleic acid.

The mouse midpregnancy lactogen or placental lactogen I (mPL-I) is encoded by a 1.0-kilobase mRNA that appears transiently during gestation, with maximal amounts accumulating in the placenta at day 10 of pregnancy. Several cDNA clones for mPL-I have been isolated from a lambda gt11 expression library constructed from day 10-placental RNA. The cDNA sequence indicates that mPL-I is synthesized as a 224 amino acid precursor, and is secreted as a 194 amino acid glycosylated hormone. The deduced amino acid sequence of mPL-I is highly homologous to the known members of the PRL family in the mouse, and hybridization analysis indicates that the mouse genome contains several mPL-I genes. Introduction of the mPL-I cDNA in an expression vector into cultured mouse cells results in the synthesis and secretion of glycosylated mPL-I protein that is recognized by anti-mPL-I antiserum and is biologically active.

Amino Acid Sequence↗
PubMed1986

Molecular cloning of mouse placental lactogen cDNA.

We have isolated a cDNA clone for the 23-kDa mouse placental lactogen II (mPL-II) from a phage lambda gt11 expression library containing cDNA synthesized from BALB/c placental RNA. Translation in vitro of placental mRNA selected by hybridization to the mPL-II cDNA clones yields a 26-kDa polypeptide that is the size of the expected precursor protein and that is immunoprecipitated with anti-mPL-II antiserum. The mPL-II cDNA clones hybridize to a 1.0-kilobase placental-specific mRNA. This mRNA, found in the fetal portion of the placenta, appears as early as day 10 of gestation and increases to a maximal level by day 12. The mPL-II cDNA nucleotide sequence has been determined. This sequence contains an open reading frame encoding a polypeptide of 222 amino acids with the amino-terminal 31 amino acids forming the signal sequence for secretion. The predicted secreted protein has 51% amino acid homology with mouse prolactin.

Amino Acid Sequence↗
PubMed1986

Expression of multiple proliferin genes in mouse cells.

Several copies of the prolactin-related proliferin gene were detected in the mouse genome, encoding at least two distinct forms of proliferin. These forms correspond to proliferin cDNA clones derived from BALB/c 3T3 tissue culture and BALB/c placental RNA. Tissue culture and placental cells were each found to express both forms of proliferin.

Amino Acid Sequence↗
PubMed1985

Nucleotide sequence of mouse prolactin and growth hormone mRNAs and expression of these mRNAs during pregnancy.

The mRNAs for mouse prolactin and growth hormone have been isolated from anterior pituitary glands and cloned as cDNAs. The nucleotide sequences of these mRNAs have been determined, and these sequences, along with the predicted amino acid sequences, are compared to those of other mammalian prolactin and growth hormone mRNAs. Levels of prolactin and growth hormone mRNAs during pregnancy have been monitored by hybridization to the cloned cDNA probes. We find the levels of these mRNAs to remain nearly constant during mid-to-late gestation.

Amino Acid Sequence↗
PubMed1985

A new member of the prolactin-growth hormone gene family expressed in mouse placenta.

Mouse placenta has been found to contain an mRNA that encodes a previously unidentified member of the prolactin-growth hormone family. This 1.1-kb mRNA (designated PRP mRNA) was detected as a cDNA clone that hydridized to a cDNA clone of mouse proliferin, a recently described growth-associated placental protein related to prolactin. PRP mRNA levels are highest in the fetal part of the placenta and peak at day 12 of gestation, decreasing gradually until term. The 972-bp sequence of PRP mRNA, determined from two cDNA clones, encodes a protein of 244 amino acid residues that has a hydrophobic leader sequence. The protein encoded by PRP mRNA has significant homology to all of the members of the prolactin family, yet is different from each of them; it also differs from mouse placental lactogen. Nucleotide sequence homology is most extensive between PRP and proliferin mRNAs, particularly at their 5' ends, where they share 92 of the first 97 nucleotides.

Amino Acid Sequence↗
PubMed1985

Identification of proliferin mRNA and protein in mouse placenta.

Proliferin is a recently described, prolactin-related protein whose mRNA appears in several murine cell lines during active growth. We have surveyed a number of mouse organs or tissues for the presence of mRNAs that hybridize to cloned proliferin cDNA. Of the tissues tested, only the placenta yielded proliferin-related mRNA. This placental RNA is about 1 kilobase in length, increases sharply between days 8 and 10 of pregnancy, and then gradually declines through day 18. It is more abundant in RNA extracted from the fetal, compared to the maternal, part of the placenta. From a cDNA plasmid library prepared from poly(A)+ placental RNA, two types of proliferin-related clones were isolated, differing in intensity of hybridization to proliferin cDNA. By nucleotide sequence analysis, a strongly hybridizing clone was found to be nearly identical to the proliferin cDNA clone isolated from a library prepared from mRNA of a growing mouse fibroblastic cell line. Using an antiserum prepared against a synthetic proliferin fusion protein, we show that proliferin is secreted as a glycoprotein by minced placental tissue and that it differs from mouse placental lactogen. We conclude that proliferin is a placental hormone that is synthesized in certain mouse cell lines during active growth. Its function during pregnancy and during the growth of cultured cells is presently unknown.

Amino Acid Sequence↗
PubMed1984

Nucleotide sequence of a growth-related mRNA encoding a member of the prolactin-growth hormone family.

As part of the proliferative response to serum, mouse 3T3 cells produce a set of growth-related mRNAs identified by hybridization to cloned cDNAs. One of these mRNAs, which is about 1 kilobase long, appears within a few hours after stimulation of resting cells with serum or platelet-derived growth factor and reaches a high level during the transition from the G1 to the S phase of growth. This mRNA is translated in vitro into a protein of approximately 25 kilodaltons. The corresponding cloned cDNA of 791 base pairs has been sequenced; it contains a single open reading frame that encodes a protein of 224 amino acids with extensive sequence homology to mammalian prolactins. The initial 29-amino acid segment of the encoded protein resembles the signal sequences of prehormones. That the growth-related protein is not mouse prolactin is indicated by comparison of its predicted amino acid composition with that of mouse prolactin and by the distinct fragment patterns seen when restricted mouse DNA is probed with the cloned cDNA or rat prolactin cDNA. Therefore, the growth-related protein appears to be a new member of the prolactin-growth hormone family. Because of its relationship to prolactin and growth hormone and its association with cell proliferation, the protein has been called "proliferin."

Amino Acid Sequence↗
PubMed1983

Synthesis and processing of simian virus 40-specific RNA in adenovirus-infected, simian virus 40-transformed human cells.

Human simian virus 80 (SV80) cells transformed by simian virus 40 (SV40) synthesize substantial quantities of the SV40 large T-antigen (Henderson & Livingston, 1974; Tjian, 1978) and cytoplasmic, poly(A)-containing RNA species that exhibit spliced structures characteristic of the SV40, early messenger RNA species that encode both large and small T-antigens (Flint & Beltz, 1979). When SV80 cells were infected with type C adenovirus, both the synthesis of SV40 large T-antigen and the appearance in the cytoplasm of newly synthesized, SV40-specific RNA sequences were inhibited during the late phase of infection. The results of hybridization to SV40 DNA of SV80 nuclear RNA, prepared from mock- or adenovirus-infected cells after labeling for short periods in vivo or in vitro, indicated that transcription of integrated SV40 was, by contrast, not disrupted during the late phase of adenovirus infection. Poly(A)-containing, nuclear RNA species that hybridized to SV40 DNA sequences and exhibited the sizes of spliced, large and small T-antigen mRNA species were also synthesized in infected cells at a time when the corresponding mRNA sequences did not leave the nucleus. These results suggest that the failure of non-adenoviral mRNA sequences to enter the cytoplasm of adenovirus-infected cells does not reflect inhibition of either their transcription or the normal enzymatic processing reactions to which pre-mRNA species are subject. Several lines of evidence do, however, establish that nuclear, SV40-specific RNA sequences are less stable in adenovirus-infected compared to mock-infected SV80 cells.

Adenoviruses, Human↗
PubMed1983

Growth-related changes in specific mRNAs of cultured mouse cells.

A cDNA plasmid library has been constructed from the poly(A)+ RNA present in BALB/c3T3 cells after serum stimulation. Of 3,500 clones tested, approximately 0.5% contained inserts corresponding to mRNAs present at higher levels in serum-stimulated BALB/c 3T3 cell cultures than in quiescent cultures. Most of these RNA species increased 2- to 5-fold, and the kinetics of increase for various RNAs differed. One clone (28H6) hybridized to a 1-kilobase RNA species that is present at barely detectable levels in resting cells but is increased at least 15- to 20-fold after serum stimulation, reaching a maximal level coincident with the onset of DNA synthesis. This RNA was at a high level in proliferating cells but decreased rapidly as cells reached confluence. 28H6 RNA was also increased in resting cells infected with simian virus 40 or stimulated with platelet-derived growth factor.

Animals↗
PubMed1979

Characterization of a 54K dalton cellular SV40 tumor antigen present in SV40-transformed cells and uninfected embryonal carcinoma cells.

SV40 infection or transformation of murine cells stimulated the production of a 54K dalton protein that was specifically immunoprecipitated, along with SV40 large T and small t antigens, with sera from mice or hamsters bearing SV40-induced tumors. The same SV40 anti-T sera immunoprecipitated a 54K dalton protein from two different, uninfected murine embryonal carcinoma cell lines. These 54K proteins from SV40-transformed mouse cells and the uninfected embryonal carcinomas cells had identical partial peptide maps which were completely different from the partial peptide map of SV40 large T antigen. An Ad2+ND4-transformed hamster cell line also expressed a 54K protein that was specifically immunoprecipitated by SV40 T sera. The partial peptide maps of the mouse and hamster 54K protein were different, showing the host cell species specificity of these proteins. The 54K hamster protein was also unrelated to the Ad2+ND4 SV40 T antigen. Analogous proteins immunoprecipitated by SV40 T sera, ranging in molecular weight from 44K to 60K, were detected in human and monkey SV40-infected or -transformed cells. A wide variety of sera from hamsters and mice bearing SV40-induced tumors immunoprecipitated the 54K protein of SV40-transformed cells and murine embryonal carcinoma cells. Antibody produced by somatic cell hybrids between a B cell and a myeloma cell (hybridoma) against SV40 large T antigen also immunoprecipitated the 54K protein in virus-infected and -transformed cells, but did not do so in the embryonal carcinoma cell lines. We conclude that SV40 infection or transformation of mouse cells stimulates the synthesis or enhances the stability of a 54K protein. This protein appears to be associated with SV40 T antigen in SV40-infected and -transformed cells, and is co-immunoprecipitated by hybridomas sera to SV40 large T antigen. The 54K protein either shares antigenic determinants with SV40 T antigen or is itself immunogenic when in association with SV40 large T antigen. The protein varies with host cell species, and analogous proteins were observed in hamster, monkey and human cells. The role of this protein in transformation is unclear at present.

Animals↗