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Expression of alternatively terminated unusual human butyrylcholinesterase messenger RNA transcripts, mapping to chromosome 3q26-ter, in nervous system tumors.

To study the molecular origin of the altered regulation of butyrylcholinesterase (BuChE) in nervous system tumors, BuChE complementary DNA (cDNA) sequences from human glioblastoma and neuroblastoma cDNA libraries were compared with BuChE cDNAs from normal fetal and adult tissues. A single 2.6-kilobase BuChE cDNA sequence was found in all normal tissues, whereas an additional alternatively terminated BuChE cDNA clone was found in both tumor libraries. The tumor-specific cDNA contained a 3',0.7-kilobase nontranslatable extension, as well as several nucleotide alterations in the normal polyadenylation site. Single-base mutations in the coding region of this unusual BuChE cDNA infer two amino acid substitutions: Asp70----Gly and Ser425----Pro. The Asp70----Gly change has recently been implicated with "atypical" BuChE, which is deficient in its capacity to hydrolyze succinylcholine. The 3.6-kilobase mRNA was less abundant in RNA blot hybridization than the 2.6-kilobase mRNA, which is in agreement with the low ratios between the 3.6- and 2.6-kilobase BuChE cDNA clones in glioblastoma and neuroblastoma libraries. Furthermore, size fractionation and microinjection of glioblastoma polyadenylated RNA, followed by enzyme activity and selective inhibition measurements, demonstrated two peaks of functional BuChE mRNA, the heavier one probably reflecting the longer transcripts. Chromosomal mapping of the 0.7-kilobase 3' fragment by in situ hybridization localized it to a unique 3q26-ter position, where we recently found an inheritably amplified "silent" defective CHE gene in a family exposed to the cholinesterase inhibitor methyl parathion. Our findings confirm previous genetic linkage mapping of the functional CHE gene to the 3q26-ter position and demonstrate that extended functional mRNA transcripts encoding a BuChE form with two modified amino acids are produced from this gene in glioblastoma and neuroblastoma cells.

Base Sequence↗

[Pepsinogen messenger RNA of human gastric mucosa and stomach cancer].

The cell-free translation method has shown that pepsinogen mRNA is a predominant fraction in the total poly(A)+ RNA from human gastric mucosa. The pepsinogen protein with the molecular weight of 45 kDa has been identified. The level of pepsinogen mRNA decreased in tumours as compared with normal mucosa but in most cases pepsinogen mRNA synthesis depression was not total.

Electrophoresis, Polyacrylamide Gel↗

[Degradation of messenger RNA, ribosomal RNA and 2-5A-dependent inhibition of protein biosynthesis].

In rabbit reticulocyte lysates the addition of exogenous 2-5A leads after 10-20 minutes to the inhibition of protein synthesis. This inhibition can be blocked by rat antiserum to 2-5A. In intact ribosomes the ribosomal RNA is cleaved after 2-5A addition, but this cleavage is not in correlation with the protein synthesis shutoff. Ribosomal 5S RNA and 5,8S RNA are not cleaved even after several hours of incubation with 2-5A. The degradation of polysome associated mRNA correlates with the protein synthesis inhibition as revealed by Northern blot hybridization of globin mRNA with 32P-labelled p beta G plasmid. The addition of 2-5A antiserum to the rabbit reticulocyte lysate also inhibits the degradation of polysome bound globin mRNA.

2',5'-Oligoadenylate Synthetase↗

Detection of Ki-ras messenger RNA in normal and chemically transformed hamster oral keratinocytes.

The cheek pouch of the Syrian hamster is an excellent model for the experimental study of oral carcinogenesis. The carcinogenic chemical 7,12-dimethylbenz[a]anthracene consistently produces epidermoid carcinomas in the cheek pouch of the Syrian hamster, giving rise to characteristic histopathological lesions in a time-dependent manner. We now present experimental evidence that c-Ki-ras mRNA can be detected in all 7,12-dimethylbenz[a]anthracene-induced tumors examined (in vivo and in vitro) in this experimental oral cancer model while no detectable c-Ki-ras mRNA can be found in the normal hamster cheek pouch epithelium. Cellular synchronization experiments using a cell line (hamster cheek pouch carcinoma cell line 1) derived from one of these 7,12-dimethylbenz[a]anthracene-induced hamster oral tumors revealed that the c-Ki-ras protooncogene is expressed during the G1 phase of the cell cycle (proliferation dependent). Serum starvation and RNA synthesis inhibition experiments using hamster cheek pouch carcinoma cell line 1 cells suggest that the c-Ki-ras protooncogene is indeed quiescent in the normal hamster cheek pouch epithelium and that failure to detect its mRNA is not related to the slower proliferation of the normal epithelial cells. These results suggest that the transcription of the c-Ki-ras protooncogene is associated with malignant transformation in the cheek pouch of the Syrian hamster.

9,10-Dimethyl-1,2-benzanthracene↗

Detection of transforming growth factor-alpha messenger RNA in normal and chemically transformed hamster oral epithelium by in situ hybridization.

We have recently demonstrated the consistent detection of transforming growth factor alpha (TGF-alpha) in chemically transformed hamster oral tumors. By Northern blot analysis, no TGF-alpha mRNA can be detected in normal cheek pouch mucosa. The consistent expression of TGF-alpha associated with the malignant transformation in the well-defined hamster oral cancer model prompted us to hypothesize that the aberrant expression of this important cellular gene could be related to a specific stage of epithelial alteration. In situ hybridization was used to test this hypothesis. We now report that by in situ hybridization we can detect TGF-alpha mRNA in normal hamster oral epithelium and also at all stages of transformation. In all epithelium, labeling of TGF-alpha mRNA in the basal layer is more pronounced than that observed in the spinous and squamous layers. There is a significant increase of TGF-alpha mRNA labeling early in 7,12-dimethylbenz(a)anathracene-induced oral carcinogenesis. This increase is associated with morphological changes of epithelial hyperplasia or dysplasia. Although lesions exhibiting full-thickness epithelial dysplasia (carcinoma in situ) showed more labeling of TGF-alpha mRNA than do areas of lesser dysplasia, the transition to full-fledged papillary or invasive squamous cell carcinoma is not associated with further elevations of TGF-alpha expression.

9,10-Dimethyl-1,2-benzanthracene↗

Interaction of bovine mitochondrial ribosomes with messenger RNA.

The gene for subunit II of cytochrome oxidase (CoII) from bovine mitochondria has been cloned behind a T7 promoter and the corresponding mRNA synthesized in vitro. The RNA transcribed from this vector has a single nucleotide 5' to the start AUG and, thus, corresponds closely to the native mRNA. It binds to the small 28 S ribosomal subunit of bovine mitochondria but not to the large (39 S) subunit or to 55 S ribosomes. The binding occurs readily in the absence of auxiliary initiation factors or initiator tRNA. The complex formed appears to contain 1 mRNA/28 S subunit. The observed binding is specific for mRNA since neither tRNA nor ribosomal RNA can act as competitive inhibitors. The interaction of the mRNA with the 28 S subunit does not require an AUG codon near the 5' end and constructs containing 5' leaders of more than 100 nucleotides still bind efficiently. About 5% of the bound mRNA is protected from digestion by T1 RNase. The protected fragments do not arise from a specific region of the mRNA since they hybridize to several restriction fragments of the cloned CoII gene.

Animals↗

Polyadenylate polymerases from normal and cancer cells and their potential role in messenger RNA processing: a review.

Two structurally and immunologically distinct species of nuclear polyadenylate [poly(A)] polymerases have been characterized. One of these enzymes is relatively absent in normal tissues but is predominant in primary and transplanted tumors and transformed cell lines. The presence of the tumor type enzyme in fetal liver, but not in regenerating liver, suggests that it is an oncofetal protein. Antibodies against the tumor-type poly(A) polymerases are present in the sera of rats bearing tumors and in some cancer patients. These antibodies are also found in the sera of rats fed hepatocarcinogen even before preneoplastic nodules were visible, which suggests that elicitation of these antibodies is an early event in neoplastic transformation. Autoantibodies against both liver-type and tumor-type poly(A) polymerase are also present in some rheumatic autoimmune sera. Polyclonal antibodies against purified enzyme from a rat hepatoma, which exhibit a single band upon immunoblot analysis, were used in cell-free extracts to study the role of poly(A) polymerase in the 3'-end processing of pre-mRNA. These studies showed that the antibodies blocked both endonucleolytic cleavage and poly(A) addition at the cleavage site and complex formation between factors in the extract and pre-mRNA. Independent studies in other laboratories have demonstrated that both the cleavage and poly(A) polymerase activities require the same component for their function. These observations suggest that both cleavage and polyadenylation reactions are tightly coupled in a functional complex.

Animals↗

[Template activity of poly(A+) and poly(A-) messenger RNA of pathogenic arenaviruses].

The total RNA from cells infected with Machupo and Lassa viruses as well as poly(A+) and poly(A-) fractions of the RNA were translated in the cell-free protein synthesizing system from rabbit reticulocytes. The translated products were treated with specific antibodies and analyzed in polyacrylamide gel electrophoresis. Only poly(A-) fraction of RNA coded for the synthesis of NP protein in vitro. The mRNAs for NP protein of Machupo and Lassa viruses are supposed to contain no poly(A) sequences at 3'end, or if they really do, the size of the sequences is not adequate for binding with oligo(dT)-cellulose.

Animals↗

Molecular mechanisms of the antiviral action of interferon: effects of interferon on the transcription of viral messenger RNA.

Evidence from a number of virus-cell systems, discussed above and in other papers in this section, shows that the resistance to virus infection induced by interferon is characterized by inhibition of both primary transcription and translation. This may be because interferon induces two (or more) distinct "antiviral proteins" which inhibit, respectively, the transcription and the translation of virus genetic information. Although both may be present in interferon treated cells, the one which is manifest in any given experimental system may depend on whether transcription or translation is the primary event in the replication of the particular virus, and upon the accessibility of the viral nucleic acid. Alternatively, inhibition of transcription and translation may be mediated by a single antiviral protein which is able to distinguish viral from cellular nucleotide sequences in both DNA and RNA. The interferon-induced ribosome-associated inhibitors of viral mRNA translation (see related papers in this section) are prime candidates for such an antiviral protein.

DNA Viruses↗

Investigations on the messenger RNA binding site of eukaryotic ribosomes by using reactive oligo(U) derivatives.

Dodecauridylate bearing a slowly alkylating reactive group in 5'-position, when bound as a mRNA analogue to rat liver ribosomes, labels preferentially proteins of the small ribosomal subunit, in particular, protein S 26.fDodecauridylate bearing an identical reactive group in 3'-position labels mainly rRNA o both subunits and proteins to less than 10%, among which S3/3a are the main targets. The results together with earlier findings support the localization of protein S 26 near the ribosomal P site and S 3/3a near the A site as well as the importance of rRNA of both subunits for interaction with mRNA when it passes the region in front of the decoding site.

Animals↗

Quantitation and localization of globin messenger RNA in rabbit reticulocyte lysate.

A sensitive and quantitative method is described for the determination of globin mRNA distribution in rabbit reticulocyte lysate. The method uses high resolution sucrose density gradient centrifugation followed by [5'-3H]polyuridylate hybridization to poly(A)-mRNA in gradient fractions. Polyadenylate, purified globin mRNA, and ribonuclease-treated lysate are used to standardize the hybridization assay. It is demonstrated that changes of mRNA and ribosomal distribution do not affect quantitation of the total mRNA localization and Met-tRNAf which suggest that the monitoring of Met-tRNAf binding alone may not be sufficient to assess the mechanisms of control which affect the initiation of protein synthesis.

Animals↗