Molecular cloning and sequence analysis of cDNA for the catalytic subunit 1 alpha of rat kidney type 1 protein phosphatase, and detection of the gene expression at high levels in hepatoma cells and regenerating livers as compared to rat livers.

A cDNA clone containing the full coding sequence of a type 1 protein phosphatase catalytic subunit 1 alpha has been isolated from a rat kidney lambda gt 10 library. The protein sequence deduced from the cDNA contains 330 amino acid residues with a molecular mass of 38 kDa. The cDNA clone from rat kidney was 89% identical at the nucleotide level in the coding region to type 1 protein phosphatase 1 alpha from rabbit skeletal muscle. However, the two protein sequences were completely identical. The type 1 alpha protein phosphatase from rat kidney shows 49% homology of amino acid sequence to the rat type 2A alpha protein phosphatase. Thus, the protein sequence of type 1 alpha protein phosphatase was completely conserved between rat and rabbit. The mRNA levels of type 1 protein phosphatase were determined in rat liver, AH13, a strain of rat hepatoma, and regenerating rat liver by Northern blot analysis using the cDNA fragment as a probe, under which conditions a single mRNA of 1.5 kb was detected. The mRNA levels of AH13 were remarkably increased when compared to those of normal ivers, whereas the mRNA levels of regenerating livers were slightly but significantly increased. These results demonstrate a marked increase in gene expression of type 1 protein phosphatase in hepatoma cells, suggesting an important role of the type 1 protein phosphatase in hepatocarcinogenesis.     

Molecular cloning of a cDNA coding for 70 kilodalton subunit of soluble guanylate cyclase from rat lung

A complementary DNA clone corresponding to the 70 kDa subunit of soluble guanylate cyclase (EC 4.6.1.2) of rat lung has been isolated. The primary structure of the cDNA consisted of 3063 nucleotides including a 1857-nucleotide coding region for 619 amino acids, and the calculated molecular weight was 70476. Blot hybridization of total poly(A)+RNAs from rat tissues detected a mRNA of about 3.4 kilobases. The amount of mRNA was abundant in lung, cerebrum and cerebellum, moderate in heart and kidney, and low in liver and muscle. Southern blot analysis of high molecular weight genomic DNA from rat liver indicated the presence of one gene in the rat haploid genome. The amino acid sequence of the 70 kDa subunit has partial homology with particulate guanylate cyclase from sea-urchin sperm, and protein phosphatase inhibitor I.     

Rat apolipoprotein E mRNA. Cloning and sequencing of double-stranded cDNA

A 900-base pair clone corresponding to rat liver apolipoprotein E (apo-E) mRNA, and containing a 3'-terminal poly(A) segment, was identified from a library of rat liver cDNA clones in the plasmid pBR322 by specific hybrid selection and translation of mRNA. A restriction endonuclease DNA fragment from this recombinant plasmid was used to clone the 5'-terminal region of the apo-E mRNA by primed synthesis of cDNA. A portion of the double-stranded cDNA corresponding to the 3'-terminal region of apo-E mRNA was subcloned into the bacteriophage M13mp7 and employed as a template for the synthesis of a radioactively labeled, cDNA hybridization probe. This cDNA probe was used in a RNA-blot hybridization assay that showed the length of the apo-E mRNA to be about 1200 nucleotides. The hybridization assay also demonstrated that apo-E mRNA is present in rat intestine, but at about a 100-fold lower level than that of the rat liver. The nucleotide sequence of rat liver apo-E mRNA was determined from the cloned, double-stranded cDNAs. The amino acid sequence of rat liver apo-E was inferred from the nucleotide sequence, which showed that the mRNA codes for a precursor protein of 311 amino acids. A comparison to the NH2-terminal amino acid sequence of rat plasma apo-E indicated that the first 18 amino acids of the primary translation product are not present in the mature protein and are probably removed during co-translational processing. The coding region was flanked by a 3'-untranslated region of 109 nucleotides, which contained a characteristic AAUAAA sequence that ended 13 nucleotides from a 3'-terminal poly(A) segment. At the 5'-terminal region of the mRNA, 23 nucleotides of an untranslated region were also determined. The inferred amino acid sequence of mature rat apo-E, which contains 293 amino acids, was compared to the amino acid sequence of human apo-E, which contains 299 amino acids. Using an alignment that permitted a maximum homology of amino acids, it was found that overall, 69% of the amino acid positions are identical in both proteins. The amino acid identities are clustered in two broad domains separated by a short region of nonhomology, an NH2-terminal domain of 173 residues where 80% are identical, and a COOH-terminal domain of 84 residues where 70% are identical. These two domains may be associated with specific functional roles in the protein.     

Isolation and characterization of two types of cDNA for mitochondrial adenylate kinase and their expression in Escherichia coli

Two cDNA clones for mitochondrial adenylate kinase were isolated from a cDNA library of bovine liver poly(A)+ RNA by using synthetic oligodeoxynucleotides as probes. The clone containing a 0.9-kilobase insert had the reading frame for a 241-residue protein (AK2A), while the other clone containing a 1.6-kilobase insert had the frame for a 234-residue protein (AK2B). Nucleotide sequences of these two clones were the same in the 5' portion up to the coding sequence for the 233rd residue, but different in the remaining 3' portions. The reported amino acid sequence of mitochondrial adenylate kinase from bovine heart corresponded to AK2A. Neither AK2A nor AK2B had a cleavable NH2-terminal presequence as that found in other imported mitochondrial proteins. RNA blot analysis of poly(A)+ RNAs from bovine liver and heart revealed three species of mRNA with approximate sizes of 0.9, 1.4, and 1.7 kilobases. The 1.7- and 1.4-kilobase species were specific for AK2B, whereas the 0.9-kilobase species was specific for AK2A. In the liver, the 1.7-kilobase mRNA was more abundant, whereas in the heart the 0.9-kilobase mRNA was predominant. The 1.4-kilobase mRNA was present only in the heart. The AK2A- and AK2B-coding sequences were expressed in Escherichia coli cells under the control of trc promoter. Both the products reverted the temperature-sensitive phenotype of the adenylate kinase mutant of E. coli.     

Tissue-specific expression of rat aldolase A mRNAs. Three molecular species differing only in the 5'-terminal sequences

Three species of aldolase A mRNA (mRNAs I, II, and III) only differing in the structure of the 5'-terminal noncoding region were detected in rat tissues. The cDNA clones for mRNAs II and III were prepared from ascites hepatoma AH60C and sequenced. The mRNA II is 1393 nucleotides long excluding poly(A) tail, while the mRNA III is 1440 nucleotides long, some 50 nucleotides longer than the mRNA II. The mRNAs II and III differ in the sequence between -25 and the 5' termini from the previously reported skeletal muscle aldolase A mRNA (mRNA I, 1343 nucleotides long). By contrast, the residual 5' noncoding sequence (-24 to -1) and the coding and 3' noncoding sequences are common to all the mRNAs. By dot spot hybridization and S1 mapping the distribution of these mRNAs in the various tissues was determined. The mRNA I appears exclusively in a skeletal muscle and some in heart and hepatoma AH60C, whereas the mRNAs II and III appear more or less in all the tissues examined, implying that their appearances are under tissue-specific control. Furthermore, partial nucleotide sequence analysis of the fetal liver aldolase A mRNA supports that aldolase A mRNA that reappeared in hepatoma is really a resurgence of the gene product expressed in the fetus.     

Demonstration of transthyretin mRNA in the brain and other extrahepatic tissues in the rat

Studies were conducted to ascertain if transthyretin mRNA was present in extrahepatic tissues of the rat. A trnasthyretin cDNA clone was isolated from a lambda gt11 human liver cDNA library by antibody screening and its identity was confirmed by nucleotide sequence analysis. This transthyretin cDNA clone was used to survey poly(A+) RNA isolated from 12 different rat tissues for transthyretin mRNA by Northern blot analysis. The liver contained the highest level of transthyretin mRNA and this level was not altered by the vitamin A status of the rat. A significant amount of transthyretin mRNA was found in the brain (30% of the level of the liver) which was localized in specific regions of the brain. In addition, detectable levels of transthyretin mRNA (1% to 2% of that of the liver) were observed in the stomach, heart, skeletal muscle, and spleen. Translation of brain poly(A+) RNA in rabbit reticulocyte lysates and immunoprecipitation of the translation products with anti-transthyretin antiserum resulted in a protein band of the same size as liver pre-transthyretin. Liver pre-transthyretin was processed by the cotranslational addition of dog pancreas microsomal membranes to a protein that migrated coincidentally with monomeric serum transthyretin. These data suggest that transthyretin in the brain and the cerebrospinal fluid results from de novo synthesis and that transthyretin may play a significant physiological function, as yet unknown, within the nervous system.     

Human elongation factor 1 beta: cDNA and derived amino acid sequence.

From a cDNA library in lambda gt11 derived from poly (A+)RNA of human ovarian granulosa cells a cDNA clone lambda HGP34, containing an EcoRI insert of 829 bp, was identified. After subcloning of the insert into pUC18, the clone pHGP34 was obtained and sequenced. The derived amino acid sequence, corresponding to a protein of 225 amino acids, shows a high degree of homology to elongation factor 1 beta (EF-1 beta) of Artemia salina (57%) and known peptide sequences of Xenopus laevis EF-1 beta (86%). We therefore assume that the protein coded for by pHGP34 represents human EF-1 beta. Northern analysis reveals an EF-1 beta specific mRNA of 900 bp. Southern analysis indicates that EF-1 beta in the human genome, like EF-1 alpha, appears to be specified by more than one gene. A high degree of sequence homology for EF-1 beta specific sequences is observed for bovine, rat and mouse species.     

Rat liver glutathione S-transferases. Complete nucleotide sequence of a glutathione S-transferase mRNA and the regulation of the Ya, Yb, and Yc mRNAs by 3-methylcholanthrene and phenobarbital

With the use of cDNA probes reverse transcribed from purified glutathione S-transferase mRNA templates, four cDNA clones complementary to transferase mRNAs have been identified and characterized. Two clones, pGTB38 and pGTB34, have cDNA inserts of approximately 950 and 900 base pairs, respectively, and hybridize to a mRNA(s) whose size is approximately 980 nucleotides. In hybrid-select translation experiments, pGTB38 and pGTB34 select mRNAs specific for the Ya and Yc subunits of rat liver glutathione S-transferases. Clone pGTB33, which harbors a truncated cDNA insert, hybrid-selects only the Ya mRNA. All of the clones, pGTB38, pGTB34, and pGTB33, hybrid-select another mRNA which is specific for a polypeptide with an electrophoretic mobility slightly greater than the Ya subunit. The entire nucleotide sequence of the full length clone, pGTB38, has been determined and the complete amino acid sequence of the corresponding polypeptide has been deduced. The mRNA codes for a protein comprising 222 amino acids with Mr = 25,547. We have also identified a cDNA clone complementary to a Yb mRNA of the rat liver glutathione S-transferases. This clone, pGTA/C36, hybrid-selects only Yb mRNA(s) and hybridizes to a mRNA(s) whose size is approximately 1200 nucleotides. Although the Ya, Yb, and Yc mRNAs are elevated coordinately by phenobarbital and 3-methylcholanthrene, the Ya-Yc mRNAs are induced to a much greater extent compared to the Yb mRNA(s). These data suggest that the mRNAs for each transferase isozyme are regulated independently.     

Primary structure of human nuclear ribonucleoprotein particle C proteins: conservation of sequence and domain structures in heterogeneous nuclear RNA, mRNA, and pre-rRNA-binding proteins.

In the eucaryotic nucleus, heterogeneous nuclear RNAs exist in a complex with a specific set of proteins to form heterogeneous nuclear ribonucleoprotein particles (hnRNPs). The C proteins, C1 and C2, are major constituents of hnRNPs and appear to play a role in RNA splicing as suggested by antibody inhibition and immunodepletion experiments. With the use of a previously described partial cDNA clone as a hybridization probe, full-length cDNAs for the human C proteins were isolated. All of the cDNAs isolated hybridized to two poly(A)+ RNAs of 1.9 and 1.4 kilobases (kb). DNA sequencing of a cDNA clone for the 1.9-kb mRNA (pHC12) revealed a single open reading frame of 290 amino acids coding for a protein of 31,931 daltons and two polyadenylation signals, AAUAAA, approximately 400 base pairs apart in the 3' untranslated region of the mRNA. DNA sequencing of a clone corresponding to the 1.4-kb mRNA (pHC5) indicated that the sequence of this mRNA is identical to that of the 1.9-kb mRNA up to the first polyadenylation signal which it uses. Both mRNAs therefore have the same coding capacity and are probably transcribed from a single gene. Translation in vitro of the 1.9-kb mRNA selected by hybridization with a 3'-end subfragment of pHC12 demonstrated that it by itself can direct the synthesis of both C1 and C2. The difference between the C1 and C2 proteins which results in their electrophoretic separation is not known, but most likely one of them is generated from the other posttranslationally. Since several hnRNP proteins appeared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as multiple antigenically related polypeptides, this raises the possibility that some of these other groups of hnRNP proteins are also each produced from a single mRNA. The predicted amino acid sequence of the protein indicates that it is composed of two distinct domains: an amino terminus that contains what we have recently described as a RNP consensus sequence, which is the putative RNA-binding site, and a carboxy terminus that is very negatively charged, contains no aromatic amino acids or prolines, and contains a putative nucleoside triphosphate-binding fold, as well as a phosphorylation site for casein kinase type II. The RNP consensus sequence was also found in the yeast poly(A)-binding protein (PABP), the heterogeneous nuclear RNA-binding proteins A1 and A2, and the pre-rRNA binding protein C23. All of these proteins are also composed of at least two distinct domains: an amino terminus, which possesses one or more RNP consensus sequences, and a carboxy terminus, which is unique to each protein, being very acidic in the C proteins and rich in glycine in A1, and C23 and rich in proline in the poly(A)-binding protein. These findings suggest that the amino terminus of these proteins possesses a highly conserved RNA-binding domain, whereas the carboxy terminus contains a region essential to the unique function and interactions of each of the RNA-binding proteins.     

Rat liver carboxylesterase: cDNA cloning, sequencing, and evidence for a multigene family

A cDNA clone was isolated from a rat liver lambda gt11 expression library by screening with polyclonal antibodies raised against a rat liver microsomal carboxylesterase. This clone of 1.8 kb contained an open reading frame encoding a mature protein of 531 amino acids with a predicted molecular weight of 58,084. The 5' portion of the clone coded for 9 amino acids of a putative signal peptide. The 3' end of the clone included an untranslated region and a poly (A) tail. Carboxylesterase active site regions, five potential N-linked glycosylation sites, and 2 postulated cystine disulfide bridges were found in the cDNA-deduced amino acid sequence. Sequences obtained from tryptic peptides and the NH2-terminus of the purified native carboxylesterase were aligned with the deduced amino acid sequence, and the overall identity was 84%. Southern blot analysis suggested the presence of multiple genes. Thus it is concluded that we have cloned a rat liver carboxylesterase, and that this enzyme is a member of a multigene family.     

Two coding regions closely linked to the rat apolipoprotein E gene: nucleotide sequences of rat apolipoprotein C-I and ECL cDNA.

Restriction fragments isolated from a 17-kb rat genomic DNA clone containing the gene for apolipoprotein (apo) E were radiolabeled and used to screen a rat liver cDNA library. A cDNA clone hybridizing to a 6-kb genomic DNA fragment was isolated and the nucleotide sequence of the cDNA insert determined. The sequence was homologous to the sequence for human apo C-I and was used to derive the corresponding amino acid sequence. Unlike human apo C-I, mature rat apo C-I contains histidine, lacks valine, and has alanine at the C terminus and aspartate as the N terminus. Screening the rat liver cDNA library with a radiolabeled 1.9-kb restriction fragment from the genomic DNA clone containing the rat apo E gene identified another cDNA clone (ECL cDNA). Nucleotide sequencing yielded a derived 75-amino-acid sequence for the ECL protein with a hydrophobicity profile similar to that of rat apo C-I. Northern analysis demonstrated a 0.50-kb band for ECL mRNA. The tissue-specific expression of the gene is similar to that of rat apo C-I. This study indicates that the rat apo C-I and ECL genes are closely linked, about 4.5 and 12 kb downstream of the apo E gene, respectively.     

Isolation and characterization of a cDNA for rat liver cysteine dioxygenase

Cysteine dioxygenase is a key enzyme of cysteine metabolism in mammals. The cDNA clones for rat liver cysteine dioxygenase were isolated by immunological screening and plaque hybridization from a rat liver cDNA library. The longest clone contained an insert of 1458 bp and encoded a polypeptide of 200 amino acids. The clone included the corresponding nucleotide sequence to amino acid sequences obtained from four lysyl endopeptidase-digested fragments of purified rat liver cysteine dioxygenase. The calculated molecular weight of rat liver cysteine dioxygenase was 23,025. Northern blot analysis revealed a single cysteine dioxygenase mRNA species of about 1.7 kb. A computer homology search indicated that this protein showed no homology with any known protein.     

Molecular cloning of cDNA for the catalytic subunit of rat liver type 2A protein phosphatase, and detection of high levels of expression of the gene in normal and cancer cells

A cloned cDNA encoding a catalytic subunit of type 2A protein phosphatase from a rat liver cDNA library was obtained by use of a synthetic oligonucleotide corresponding to the tryptic peptide sequence of the purified enzyme. There was only a single amino acid difference between the deduced amino acid sequence of the clone obtained and those of the catalytic subunits, 2A alpha, of the rabbit skeletal muscle, porcine kidney and human liver enzymes, suggesting that this clone was a rat 2A alpha cDNA. On Northern blot analysis using a cDNA fragment as a probe, three mRNA species were detected in rat liver: a major mRNA of 2.0 kb and a minor one of 2.7 kb under high stringency conditions, and also a 1.1 kb mRNA under low stringency conditions. The 2A alpha gene was found to be highly expressed in various tissues of rat, especially the brain. High levels of expression of the gene were also detected in mouse NIH3T3 cells and their transformants, and in human cancer cell lines as well as a human immortalized cell line.     

Construction of a cDNA clone for a nuclear-coded subunit of cytochrome c oxidase from rat liver

A cDNA library for 6S-9S poly(A)-containing RNA from rat liver was constructed in E. coli. Initial screening of the clones was carried out using single stranded 32P-labeled cDNA prepared against poly(A)-containing RNA isolated from immunoadsorbed polyribosomes enriched for the nuclear-coded subunit messenger RNAs of cytochrome c oxidase. One of the clones, pCO89, was found to hybridize with the messenger RNA for subunit VIC. The DNA sequence of the insert in pCO89 was carried out and it has got extensive homology with the C-terminal 33 amino acids of subunit VIC from beef heart cytochrome c oxidase. In addition, the insert contained 146 bp, corresponding to a portion of the 3'-non-coding region. Northern blot analysis of rat liver RNA with the nick-translated insert of pCO89 revealed that the messenger RNA for subunit VI would contain around 510 bases.     

Selection of a cDNA clone which contains the complete coding sequence for the mature form of ornithine transcarbamylase from rat liver: expression of the cloned protein in Escherichia coli. Molecular cloning of rat ornithine transcarbamylase

A cDNA clone corresponding to the mature form of ornithine transcarbamylase (OTCase) was selected from a rat liver cDNA library constructed in bacteriophage lambda gt10. OTCase clones were selected using a synthetic DNA probe of 15 bases corresponding to the 3' end of the OTCase mRNA [Horwich, A. L., Kraus, J.P., Williams, K., Kalousek, F., K?nigsberg, W. & Rosenberg, L.E. (1983) Proc. Natl Acad. Sci. USA, 80, 4258-4262]. Putative OTCase clones were subcloned into the expression vector, pUC9, and the identity of inserts confirmed by colony immunoassay and by electrophoretic transfer of cloned proteins from sodium dodecyl sulphate/polyacrylamide gels to nitrocellulose filters followed by probing with monospecific anti-OTCase antibodies and 125I-labelled protein A. A clone corresponding to the full-length mature form of rat liver OTCase (plus 15 amino acids from Escherichia coli beta-galactosidase) was obtained and the identity of the clone was confirmed by comparison of the 5' sequence with a limited N-terminal amino acid sequence [Lusty, C., Jilka, R. L. & Nietsch, E. H. (1979) J. Biol. Chem. 254, 10030-10036]. A sequence discrepancy between the published sequence (Lusty et al.) and the sequence predicted from the cDNA structure is noted.     

Retinol-binding protein messenger RNA levels in the liver and in extrahepatic tissues of the rat

A retinol-binding protein (RBP) cDNA clone was used to examine the effect of retinol status on the level of RBP mRNA in the liver, and to explore whether extrahepatic tissues contain RBP mRNA. In the first series of experiments, poly(A+) RNA was isolated from the livers of normal, retinol-depleted, and retinol-repleted rats and the levels of RBP mRNA in these samples were determined by both Northern blot and RNA Dot blot analyses. The levels of RBP mRNA in liver were similar in all three groups of rats. These findings confirm and extend previous studies which showed that retinol did not alter the in vivo rate of RBP synthesis or the translatable levels of RBP mRNA. In a second series of experiments, the RBP cDNA clone was used to survey poly (A+) RNA isolated from 12 different rat tissues for RBP mRNA by Northern blot analysis. We found that, along with the liver, many extrahepatic tissues contained RBP mRNA. Kidney contained RBP mRNA at a level of 5-10% of that of the liver, and the lungs, spleen, brain, stomach, heart, and skeletal muscle contained 1-3% of that of the liver. Translation of kidney poly (A+) RNA in rabbit reticulocyte lysates and immunoprecipitation of the translation products with anti-RBP antiserum resulted in a protein band of the same size as liver preRBP. These data suggest that RBP is synthesized in many extrahepatic tissues.It is possible that this extra-hepatically synthesized RBP may function in the recycling of retinol from these tissues back to the liver or to other target organs.