Differential accumulation of potato tuber mRNAs during the hypersensitive response induced by arachidonic acid elicitor

Accumulation of messenger RNAs in potato tuber discs was analysed during the hypersensitive response induced by treatment with the biotic elicitor arachidonic acid. In vitro translation of polysomal poly(A)⁺ RNAs indicated that the accumulation of some sixteen mRNAs varied following treatment with arachidonic acid, and that the level of thirteen of these was increased. Two cDNA closes (pSTH-1 and-2) were isolated from a library of elicitor-treated tissue cDNAs. Northern blot analysis using these clones as molecular probes indicated that the levels of at least two mRNAs were markedly increased after elicitor treatment. In hybrid-released translation experiments, each of the cDNA clones selected more than one mRNA. Translation of these mRNAs yielded two polypeptides of M_r 45 000 (for the pSTH-1 clone), and three polypeptides of M_e 17 000 (for the pSTH-2 clone). The low molecular weight polypeptides may correspond to potato pathogenesis-related (PR) proteins.     

The chromosomal gene structure and two mRNAs for human granulocyte colony-stimulating factor.

Two different cDNAs for human granulocyte colony-stimulating factor (G-CSF) were isolated from a cDNA library constructed with mRNA prepared from human squamous carcinoma cells, which produce G-CSF constitutively. The nucleotide sequence analysis of both cDNAs indicated that two polypeptides coded by these cDNAs are different at one position where three amino acids are deleted/inserted. When the two cDNAs were introduced into monkey COS cells under the SV40 early promoter, both of them produced proteins having authentic G-CSF activity and some difference in the specific activity was suggested. A human gene library was then screened with the G-CSF cDNA and the DNA fragment containing the G-CSF chromosomal gene was characterized by the nucleotide sequence analysis. The human G-CSF gene is interrupted by four introns and a comparison of the structures of the two G-CSF cDNAs with that of the chromosomal gene indicated that the two mRNAs are generated by alternative use of two 5' splice donor sequences in the second intron of the G-CSF gene. When the G-CSF chromosomal gene was expressed in monkey COS cells by using the SV40 enhancer two mRNAs were detected by S1 mapping analysis.     

The house musk shrew (Suncus murinus): a unique animal with extremely low level of expression of mRNAs for CYP3A and flavin-containing monooxygenase

Expression of drug-metabolizing enzymes including cytochrome P450 (CYP) and flavin-containing monooxygenase (FMO) in various tissues of Suncus murinus (Suncus) were examined. Northern blot analysis showed that mRNAs hybridizable with cDNAs for rat CYP1A2, human CYP2A6, rat CYP2B1, human CYP2C8, human CYP2D6, rat CYP2E1, human CYP3A4 and rat CYP4A1 were expressed in various tissues from Suncus. The mRNA level of CYP2A in the Suncus lung was very high. Furthermore, it was found that the level of CYP2A mRNA in the Suncus lung was higher compared to the Suncus liver. The expression level of mRNA hybridizable with cDNA for human CYP3A4 was very low. The presence of CYP3A gene in Suncus was proven by the induction of the CYP with dexamethasone. Very low expression levels of mRNAs hybridizable with cDNAs for rat FMO1, rat FMO2, rat FMO3 and rat FMO5 were also seen in Suncus liver. No apparent hybridization band appeared when human FMO4 cDNA was used as a probe. The hepatic expression of mRNAs hybridizable with cDNAs for UDP-glucuronosyltransferase 1*6, aryl sulfotransferase, glutathione S-transferase 1, carboxyesterase and microsomal epoxide hydrolase in the Suncus were observed. These results indicate that the Suncus is a unique animal species in that mRNAs for CYP3A and FMO are expressed at very low levels.     

Molecular cloning of monkey liver cytochrome P-450 cDNAs: similarity of the primary sequences to human cytochromes P-450.

Three cDNAs coding for monkey cytochrome P-450 (P450) 2C, 2E and 3A (MKmp13, MKj1 and MKnf2, respectively) were isolated from a lambda gt11 cDNA library of a liver from a 3-methylcholanthrene (3MC)-treated crab-eating monkey, using cDNA fragments for human P450 2C, 2E and 3A as respective probes. MKmp13 and MKnf2 were 1901 and 2032 bp long, containing entire coding regions for polypeptides of 490 and 503 residues, respectively. The deduced N-terminal amino acid sequences of MKmp13 and MKnf2 were identical with those of P450-MK1 and P450-MK2, which had been purified from liver microsomes of untreated and polychlorinated biphenyl (PCB)-treated crab-eating monkeys, respectively. MKj1 was 1508 bp long, encoding a polypeptide of 449 residues, which is presumed to lack N-terminal 45 residues as compared with the sequence for human P450 2E1. Northern blot analysis indicated that monkey P450 2C, 2E and 3A mRNAs were expressed constitutively in monkey livers. P450 2E and 3A mRNAs were induced by both 3MC and PCB, while P450 2C mRNA was induced only by PCB. The deduced amino acid sequences of four monkey cytochrome P-450 cDNAs, including P450 1A1 (MKah1) which we isolated previously, were more than 92% identical with those of corresponding human cytochrome P-450 cDNAs.     

A novel alpha subunit in rat brain GABAA receptors

Two cDNAs (alpha 1 and alpha 4) from rat brain cDNA libraries encode isoforms of the alpha subunit of the GABA/benzodiazepine receptor, which differ at 30% of their amino acid residues. Northern blot analysis and in situ hybridization histochemistry show that alpha 1 and alpha 4 mRNAs have distinct sizes and distinct regional and cellular distributions in rat brain: both mRNAs are found in the cortex and hippocampus; however, only the alpha 1 mRNA is detected in the cerebellum. We injected RNA transcribed from alpha 1 and alpha 4 cDNAs into Xenopus oocytes, together with an RNA for a rat beta subunit. We obtained GABA-dependent inward currents that were reversibly blocked by picrotoxin. Picrotoxin alone, applied to oocytes producing the alpha and beta polypeptides, elicited an outward current. We suggest that these polypeptides together produce GABA-gated ion channels that can also open spontaneously.     

Cloning and characterization of DNA complementary to rat liver UDP-glucuronosyltransferase mRNA

UDP-glucuronosyltransferase (transferase) clones were isolated from a cDNA bank constructed in pBR322 using transferase-enriched mRNA from the livers of phenobarbital-treated rats. The enrichment of mRNA was accomplished by polysome immunoadsorption with antibody to purified mouse liver transferase. This antibody was shown to bind specifically to rat transferase by Ouchterlony double diffusion analysis, immunoadsorption of glucuronidating activities, and selective inhibition of the immunoadsorption of in vitro synthesized enzyme by purified rat liver transferase. The isolated clones were verified to contain DNA complementary to transferase mRNA by hybrid translation-selection. Three classes of transferase cDNAs were characterized by restriction endonuclease mapping, and the largest insert-containing clone of each class was designated pUDPGTr-1, pUDPGTr-2, and pUDPGTr-3. Their insert sizes were approximately 2,400, 2,000, and 2,000 bp, respectively. All three cDNAs hybridized with a 2,300 +/- 150 bp mRNA, and each selected the translation of a 52,000-dalton polypeptide. Immunoadsorption of the 35S-labeled translation product could be competitively inhibited in each case by the addition of purified rat liver transferase. pUDPGTr-1 and pUDPGTr-3 inserts shared extensive sequence homology. This was demonstrated by Southern blot analysis using purified inserts and electron microscopic heteroduplex analysis. Southern blot analysis revealed that these cDNAs hybridized to overlapping genomic fragments. pUDPGTr-2 shared less sequence homology with the other two classes of cDNAs, based on the above criteria. In addition, mRNA corresponding to pUDPGTr-2 was elevated 5-fold by phenobarbital treatment, whereas the other mRNAs levels were unaffected. These studies demonstrate that in rat liver there are a minimum of three distinct transferase mRNAs, two of which may be associated with a common gene or gene family.     

Cell-free translation of adenovirus 2 E1a- and E1b-specific mRNAs and evidence that E1a-related polypeptides are produced from E1a-E1b overlapping mRNA

We have characterized the polypeptides translated in vitro by mRNAs of early region 1 (E1) of human adenovirus (Ad) type 2. Poly (A+) polyribosomal RNA was isolated from early Ad2-infected cells, the viral specific mRNAs were selected by hybridization to Ad2 E1a and E1b DNA, and the mRNAs were translated in vitro using [35S]methionine as a labeled precursor with a rabbit reticulocyte lysate. E1a-selected mRNA was translated to the 45-58-kDa cluster of polypeptides. We show here that E1b-selected mRNA can also be translated to the 45-58-kDa cluster of polypeptides in addition to the major 19-kDa polypeptide. The E1b 58-kDa polypeptide was produced only at a low level unless E1b mRNA is fractionated before translation to enrich for the 58-kDa mRNA. Translation of E1b region-selected mRNAs that have been fractionated by size shows that the 22 S mRNA fraction is translated to at least the 53-58-kDa E1a-related polypeptides as well as to E1b 58- and 19-kDa polypeptides. Our experiments suggest that the 22 S mRNA fraction includes E1a-E1b overlapping mRNA which was translated to E1a-related polypeptides as well as E1b 22 S mRNA. When compared by two-dimensional gel electrophoresis and by tryptic peptide mapping, the cluster of polypeptides translated from E1a-selected mRNA and the cluster translated from E1b-selected mRNA were distinguishable. A possible explanation for this is discussed, based upon splicing sites of the E1a-E1b overlapping mRNA which would result in an amino acid sequence with a COOH-terminal end slightly different from that of E1a polypeptides.     

Characterization and regulation of testicular inhibin beta-subunit mRNA

To understand the possible structures of testicular inhibin, we have isolated cDNAs coding for inhibin subunits from human testicular cDNA libraries. In this study we report that the nucleotide and predicted amino acid sequences for human testicular inhibin beta-B-subunit are similar to those of human ovary. In rat testis two species of beta-B-subunit mRNA [4.4 and 3.3 kilobases (kb)] appeared to be present in equal concentration, as opposed to rat ovary where a predominant band of 4.4 kb and a minor band of 3.3 kb were observed. One major species of beta-A-subunit mRNA (6.5 kb) was identified in both testis and ovary. The concentration of beta-A-subunit mRNA in the testis was very low, representing only 0.5% of that in rat ovary. The accumulation of beta-B-subunit mRNA peaked at 20 days of age and declined thereafter in a pattern similar to that of the alpha-subunit gene. Hypophysectomy caused a marked increase in the concentration as well as the total content of beta-B-subunit but no change in beta-A-subunit mRNA in rat testis. We have previously reported that FSH markedly increased alpha-subunit mRNA levels both in vivo and in vitro. By contrast, neither FSH nor testosterone has any significant effect on the accumulation of beta-A- or beta-B-subunit mRNAs in hypophysectomized animals or Sertoli cell primary cultures. We conclude that 1) the mRNAs for both beta-subunits are not regulated by FSH; and 2) hypophysectomy does not change and increases, respectively, the mRNAs for the beta-A- and beta-B-subunits. We conclude that the inhibin subunit mRNAs are differentially regulated in rat testis.     

Coinduction of endothelial nitric oxide synthase and arginine recycling enzymes in aorta of diabetic rats.

Decreased availability of arginine and impaired production of NO (nitric oxide) have been implicated in the development of endothelial dysfunction. Citrulline formed by the NOS reaction is recycled to arginine by the citrulline-NO cycle, which is composed of NOS, argininosuccinate synthetase (AS), and argininosuccinate lyase. Therefore, we investigated the alterations of these enzymes in the aorta of streptozotocin (STZ)-induced diabetic rats. eNOS and AS mRNAs were increased by three- to fourfold 1-2 weeks after STZ treatment and decreased at 4 weeks. AL mRNA was weakly induced. Induction of eNOS and AS proteins was also observed. Cationic amino acid transporter (CAT)-1 mRNA remained little changed, and CAT-2 mRNA was not detected. The plasma nitrogen oxide levels were increased 1-2 weeks after STZ treatment and decreased at 4 weeks. Transforming growth factor-beta1 (TGF-beta1) mRNA in the aorta was also induced. TGF-beta1 induced eNOS and AS mRNAs in human umbilical vein endothelial cells but inhibited the proliferation of HUVEC. These results indicate that eNOS and AS are coinduced in the aorta in early stages of STZ-induced diabetic rats and that the induction is mediated by TGF-beta1. The results also suggest that TGF-beta1 works antiatherogenically at early stages of diabetes by increasing NO production, whereas prolonged elevation of TGF-beta1 functions atherogenically by inhibiting endothelial cell growth.     

Cloning and characterization of mRNA capping enzyme and mRNA (Guanine-7-)-methyltransferase cDNAs from Xenopus laevis

The mRNA cap structure, which is synthesized by a series of reactions catalyzed by capping enzyme, mRNA (guanine-7-)-methyltransferase, and mRNA (ribose-2'-O-)-methyltransferase, has crucial roles for RNA processing and translation. Methylation of the cap structure is also implicated in polyadenylation-mediated translational activation during Xenopus oocyte maturation. Here we isolated two Xenopus laevis cDNAs, xCAP1a and xCAP1b, for mRNA capping enzyme and one cDNA for mRNA (guanine-7-)-methyltransferase, xCMT1, which encode 598, 511, and 402 amino acids, respectively. The deduced amino acid sequence of xCAP1a was highly homologous to that of human capping enzyme hCAP1a, having all the characteristic regions including N-terminal RNA 5'-triphosphatase as well as C-terminal mRNA guanylyltransferase domains which are conserved among animal mRNA guanylyltransferases, whereas in xCAP1b the most C-terminal motif was missing. The amino acid sequence of xCMT1 was also similar to human (guanine-7-)-methyltransferase, hCMT1a, with all the conserved motifs among cellular (guanine-7-)-methyltransferases, except for its N-terminal portion. The recombinant xCAP1a and xCMT1 exhibited cap formation and mRNA (guanine-7-)-methyltransferase activities, respectively. RT-PCR analysis showed that mRNA for xCAP1a and xCMT1 exist abundantly in fertilized eggs as maternal mRNAs, but xCMT1 mRNA gradually decreased in its amount in later stages of early development.     

Both P1 and P2 protamine genes are expressed in mouse, hamster, and rat

To date, in mammals except for the mouse and human, only one protamine variant has been isolated from sperm. These mammalian protamines share amino acid sequence homology with mouse protamine 1 (mP1), the tyrosine-containing variant. Southern blot analysis of restriction enzyme digests of hamster and rat liver DNA reveals the presence of sequences homologous to mP1, and also to mouse protamine 2 (mP2) cDNAs. Northern blots of hamster and rat total testis RNA probed with mP2 cDNA confirm that the protamine 2 gene in these species is transcribed into two size classes of mRNA of approximately 830 and 700 nucleotides. However, the relative abundance of the rat and hamster protamine 2 mRNAs (rP2 and hP2) in total testis is approximately 50-fold lower and 2- to 5-fold lower, respectively, than the mouse protamine 2 mRNA. Northern blot analysis of hamster and rat testis polysome gradients demonstrates that although the amount of rP2 mRNA and hP2 mRNA is reduced, both are present on polysomes. The decreased expression of rat and hamster protamine 2 mRNA relative to their protamine 1 counterparts contrasts protamine expression in the mouse testis, where approximately equal amounts of mP1 and mP2 protamine mRNAs are present. These results suggest differential expression of the P1 and P2 protamine genes in three closely related mammals.     

Organization and expression of two tandemly oriented genes encoding ribulosebisphosphate carboxylase/oxygenase activase in barley

We have isolated and structurally characterized genomic DNA and cDNA sequences encoding ribulose-1,5-bisphosphate carboxylase/oxygenase (Rbu-P2 carboxylase) activase from barley (Hordeum vulgare L.). Three Rbu-P2 carboxylase activase (Rca) polypeptides are encoded in the barley genome by two closely linked, tandemly oriented nuclear genes (RcaA and RcaB); cDNAs encoding each of the three Rbu-P2 carboxylase activase polypeptides were isolated from cDNA libraries of barley leaf mRNA. RcaA produces two mRNAs, which encode polypeptides of 42 and 46 kDa, by an alternative splicing mechanism identical to that previously reported for spinach and Arabidopsis Rca genes (Werneke, J.M., Chatfield, J.M., and Ogren, W. L. (1989) Plant Cell 1, 815-825). RcaB is transcribed to produce a single mRNA, which encodes a mature peptide of 42 kDa. Genomic Southern blots indicate that RcaA and RcaB represent the entire Rbu-P2 carboxylase activase gene family in barley. The genes share 80% nucleotide sequence identity, and the 42-kDa polypeptides encoded by RcaA and RcaB share 87% amino acid sequence identity. Coding regions of the two barley Rca genes are separated by 1 kilobase pair of flanking DNA. DNA sequence motifs similar to those thought to control light-regulated gene expression in other nuclear-encoded plastid polypeptide genes are found at the 5' end of both barley Rca genes. Probes specific to three mRNAs were used to determine the relative contribution each species makes to the total Rca mRNA pool.     

Identification of mRNAs differentially expressed in quiescence or in late G1 phase of the cell cycle in human breast cancer cells by using the differential display method.

BACKGROUND: The decision for a cell to enter the DNA synthesis (S) phase of the cell cycle or to arrest in quiescence is likely to be determined by genes expressed in the late G1 phase, at the restriction point. Loss of restriction point control is associated with malignant cellular transformation and cancer. For this reason, identifying genes that are differentially expressed in late G1 phase versus quiescence is important for understanding the molecular basis of normal and malignant growth. MATERIALS AND METHODS: The differential display (DD) method detects mRNA species that are different between sets of mammalian cells, allowing their recovery and cloning of the corresponding cDNAs. Using this technique, we compared mRNAs from synchronized human breast cancer cells (21 PT) in quiescence and in late G1. RESULTS: Six mRNAs differentially expressed in late G1 or in quiescence were identified. One mRNA expressed 10 hr after serum induction showed 99% homology to a peptide transporter involved in antigen presentation of the class I major histocompatibility complex (TAP-1) mRNA. Another mRNA expressed specifically in quiescence and down-regulated 2 hr following serum induction showed 98% homology to human NADP+ -dependent cytoplasmic malic enzyme (EC1.1.1.40) mRNA, which is an important enzyme in fatty acid synthesis and lipogenesis. Three others showed high homology to different mRNAs in the GeneBank, corresponding to genes having unknown functions. Finally, one mRNA revealed no significant homology to known genes in the GeneBank. CONCLUSIONS: We conclude that DD is an efficient and powerful method for the identification of growth-related genes which may have a role in cancer development.     

Structural sequences are conserved in the genes coding for the alpha, alpha' and beta-subunits of the soybean 7S seed storage protein.

Cloned DNAs encoding four different proteins have been isolated from recombinant cDNA libraries constructed with Glycine max seed mRNAs. Two cloned DNAs code for the alpha and alpha'-subunits of the 7S seed storage protein (conglycinin). The other cloned cDNAs code for proteins which are synthesized in vitro as 68,000 d., 60,000 d. or 53,000 d. polypeptides. Hybrid selection experiments indicate that, under low stringency hybridization conditions, all four cDNAs hybridize with mRNAs for the alpha and alpha'-subunits and the 68,000 d., 60,000 d. and 53,000 d. in vitro translation products. Within three of the mRNA, there is a conserved sequence of 155 nucleotides which is responsible for this hybridization. The conserved nucleotides in the alpha and alpha'-subunit cDNAs and the 68,000 d. polypeptide cDNAs span both coding and noncoding sequences. The differences in the coding nucleotides outside the conserved region are extensive. This suggests that selective pressure to maintain the 155 conserved nucleotides has been influenced by the structure of the seed mRNA. RNA blot hybridizations demonstrate that mRNA encoding the other major subunit (beta) of the 7S seed storage protein also shares sequence homology with the conserved 155 nucleotide sequence of the alpha and alpha'-subunit mRNAs, but not with other coding sequences.