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At least 235 records · Page 13Linked to original sources
PubMed1995

Characterization of two stop codon mutations in the galactose-1-phosphate uridyltransferase gene of three male galactosemic patients with severe clinical manifestation.

Classical galactosemia, which is caused by deficiency of galactose-1-phosphate uridyltransferase, is characterized by acute problems of hepatocellular dysfunction, sepsis, cataracts and failure to thrive. Galactose limitation reverses these symptoms immediately; however, the long-term complications, such as mental retardation and ovarian failures are major problems in most of these patients. In order to investigate the molecular basis for phenotype variation in galactosemia, we have screened the most common mutation in the GALT gene, Q188R. We have further examined those patients who are heterozygous for Q188R or negative for this mutation by SSCP analysis and direct sequencing. In three male patients, we have identified, for the first time, two stop-codon mutations in the GALT gene, G212X (exon 7) and E340X (exon 10). Two patients of 8 and 28 years of age, respectively, who are compound heterozygotes for Q188R and G212X, have severe mental retardation and their general clinical condition is more severe than that of patients with missense mutations. The third patient, who is 8 years of age and who is homozygous for E340X, the N314D polymorphism and a silent substitution L218L, presents with a relatively normal physical and mental condition to date.

Adult↗
PubMed2002

A novel stop codon mutation (X465Y) in the argininosuccinate lyase gene in a patient with argininosuccinic aciduria.

Argininosuccinate lyase (ASL) deficiency (McKusick 207900) is a rare autosomal recessive disorder affecting the urea cycle. The cardinal symptom in the neonatal form is progressive hyperammonemia, which is often life-threatening. However, clinical symptoms in the late onset form are quite heterogeneous. As well as measurement of ASL activity, analysis of the ASL gene is necessary to clarify the genetic basis of various phenotypes. We report a patient with late onset argininosuccinate lyase deficiency (ASLD) who had hepatomegaly and mildly increased level of ammonia. By mutation analysis of the mRNA and genomic DNA from the patient's leukocytes, we identified a novel missense mutation 1395G>C in the homozygous state, which results in the exchange of a stop codon to tyrosine at amino acid position 465 (X465Y). This unique mutation causes an elongation of fifty amino acids in the C-terminal region of the ASL protein, and is likely related to a milder phenotype compared with previously reported mutations. In addition, this is the first report on mutation analysis in a Japanese ASLD patient.

Amino Acid Sequence↗
PubMed1994

Premature stop codons inactivate the RT6 genes of the human and chimpanzee species.

RT6 is a glycosyl phosphatidylinositol-anchored cell membrane protein, whose expression is restricted to peripheral T cells and intraepithelial lymphocytes. It has attracted interest as a T cell differentiation marker and activation antigen in rats. The only known protein to which RT6 shows significant homology is a recently cloned mono(ADP-ribosyl)transferase of rabbit skeletal muscle which is distantly related also to certain bacterial toxins. Intriguingly, whereas the rat carries a single copy RT6 gene with two known highly divergent alleles, the mouse carries two closely linked, functional RT6 genes that show approximately 85% sequence identity. We have now cloned and sequenced the homologues of the RT6 genes from humans of distinct ethnic backgrounds and of the chimpanzee. Surprisingly, in each case, three premature in-frame stop codons preclude expression of the single copy RT6 gene as a cell surface protein. Otherwise, the RT6 genes of human and chimpanzee exhibit high structural conservation to their rodent counterparts. RNA expression analyses indicate that the RT6 gene is not transcriptionally active in human T cells or any other human tissue analyzed so far. To our knowledge, RT6 represents the first mammalian membrane protein identified that has been lost universally in the human and chimpanzee species due to gene inactivation.

ADP Ribose Transferases↗
PubMed2004

Novel insertion 496_497insG creating a stop codon D194X in a Chinese family with X-Linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (XALD, MIM 300100), the commonest inherited peroxisomal disorder, is characterized by central nervous system demyelination, primary adrenal failure and the systemic accumulation of saturated very long chain fatty acids (VLCFAs). The defective gene ABCD1 encodes an ATP-binding cassette (ABC) transport protein named ALDP, which functions as a crucial transporter of VLCFAs into the peroxisomes for beta-oxidation. Here, we report a Chinese man with adrenomyeloneuropathy characterized by Addison's disease and spastic paraparesis. His plasma VLCFA levels, ratios of C24:0/C22:0 and C26:0/C22:0 were all significantly elevated. We performed mutation analysis of the ABCD1 gene in the proband and the family members using direct DNA sequencing and restriction analysis. A novel insertion 496_497insG in exon 1 causing a frame shift and a premature stop codon at amino acid position 194 (D194X) was identified (GenBank accession No. NM_000033). The insertional mutation abolishes an HhaI restriction site. The same mutation was found in his mother and the eldest sister even though their clinical and biochemical abnormalities were milder. Diagnosis of XALD often relies upon the detection of elevated VLCFA levels and ratios of C26:0/C22:0 and C24:0/C22:0 in fasting blood, however, 5-15% of the obligate heterozygotes would give normal values. DNA-based testing thus remains the most reliable tool for heterozygote detection when the disease-causing mutations are known. Using restriction fragment length polymorphism with HhaI, we have devised a rapid method for the identification of the carriers among the proband's family members and possibly for the screening of the mutations in other XALD patients.

ATP Binding Cassette Transporter, Subfamily D, Mem↗
PubMed2000

Mutations and deletions in core promoter and precore stop codon in relation to viral replication and liver damage in Singaporean hepatitis B virus carriers.

BACKGROUND: The core promoter of hepatitis B virus (HBV) is crucial for the viral replication and mutations may lead to the establishment of chronic infection and development of liver diseases. We analysed this region in Singaporean HBV carriers and assessed their association with viral replication and liver damage. MATERIALS AND METHODS: Thirty-three Singaporean HBV carriers were selected. Serological markers for HBV infection and indicators for liver functions were analysed using commercial kits. Among these patients, 17 were chronic carriers, 10 had cirrhotic livers and 6 others had hepatocellular carcinoma (HCC). The region on the HBV genome covering the entire core promoter and core gene was amplified for each patient by polymerase chain reaction. The amplified DNA fragments were sequenced and analysed. RESULTS: The incidence of mutations in the core promoter or the precore gene product (stop codon at amino acid 28) was not significantly higher compared with the wild type sequences in patients with liver damage. Most mutations in either the core promoter or precore gene significantly reduced the viral replication, as indicated by HBV DNA levels. High levels of HBV DNA were found in three mutants with deletion in the same region, presumably the binding site of liver enriched factor, within the core promoter. CONCLUSION: Our findings revealed a different mutation pattern in the core promoter in Singaporean HBV carriers. While most mutations may not be directly associated with the development of liver diseases, deletions in the core promoter could contribute to enhanced viral replication and should be studied further.

Adult↗
PubMed1991

Hepatitis B virus variant, with a deletion in the preS2 and two translational stop codons in the precore regions, in a patient with hepatocellular carcinoma.

We analyzed hepatitis B virus (HBV) genomes obtained from serum samples and liver biopsy specimen of a chronic HBsAg/anti-HBe carrier with hepatocellular carcinoma (HCC). Before the liver biopsy, performed at the time of HCC diagnosis, the patient had been followed for 2 years; the serum samples collected in that period resulted negative for HBV-DNA dot blot hybridization. The hepatic DNA was at first examined by Southern blot, but no HBV sequence was detected. Polymerase chain reaction (PCR) amplification revealed the presence of HBV genomes in DNA extracted from the liver tissue and from two serum samples collected, respectively, 1 and 2 years before the biopsy. Direct sequence of the amplified preC/C and preS regions showed that the viral populations present in serum and liver were identical and that they had a 34 nucleotide deletion in the preS2 region, while the preC region presented two mutations each introducing a translational stop codon, one at the carboxy terminal end and the other at the second codon of the region, both able to prevent HBeAg expression. These results identify a new HBV variant which was selected during a chronic infection, and had very low levels of replication as shown by its detection only after PCR amplification.

Base Sequence↗
PubMed2002

Identification of a stop codon mutation in exon 2 of the collagen 2A1 gene in a large stickler syndrome family.

PURPOSE: To describe the clinical features and identify the mutation responsible for an autosomal dominant vitreoretinal degeneration occurring in a previously unreported large family. DESIGN: Cohort study. METHODS: Family members were evaluated clinically over a 30-year period. Genealogical investigation, genetic linkage to known vitreoretinal degenerations, and mutation screening of the COL2A1 gene were performed. RESULTS: We identified a single large family (2,384 total family members) with vitreoretinal degeneration spanning 12 generations. We reviewed the clinical records of 165 family members (95 affected and 70 unaffected). The common clinical findings in affected individuals included early-onset posterior perivascular retinal degeneration, vitreous degeneration, and retinal detachment. The incidence of retinal detachment was 57% (95/165) and the mean age of onset was 15.2 years. Orofacial, skeletal, and auditory abnormalities were seen in 0%, 5%, and 7.5%, respectively, in a subset of 28 affected subjects. Linkage to the collagen COL2A1 locus was demonstrated and a cytosine to adenosine transition identified within exon 2, leading to the creation of a stop codon at position 86 (Cys86Stop). CONCLUSIONS: Identification of the mutation in this family enables diagnosis of individuals at risk for potentially blinding complications in this condition at an early age. Given the variability of the Stickler phenotype, mutation detection allows for more comprehensive genetic counseling and directs clinical monitoring to family members inheriting the disease gene.

Adolescent↗
PubMed2000

A novel frameshift mutation (2436insT) produces an immediate stop codon in the autosomal dominant polycystic kidney disease 2 (PKD2) gene.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is a genetically heterogeneous disorder that can be caused by mutations in at least three different genes. Several mutations have been identified in PKD1 and PKD2 genes. Most of the mutations found in PKD2 gene are predicted to cause premature termination of the protein. METHODS: We analysed an Argentinian family characterized previously as PKD2. The PKD2 gene was amplified from genomic DNA using 17 primer pairs and the products were analysed by heteroduplex analysis. PCR products that showed a variation by heteroduplex analysis were sequenced directly. The mutation was confirmed by sequencing relatives. The segregation of the mutation in this family was verified by restriction endonuclease digestion of PCR products obtained from genomic DNA of all family members. Results and conclusions. Here, we report a novel mutation present in an Argentinian family characterized as PKD2 by linkage analysis. The mutation, shared by all affected members of the family, is a thymidine insertion at position 2436 of the gene, which results in a translation frameshift and creates an immediate stop codon. This mutation is expected to lead to a truncated protein that lacks the interacting domain with the PKD1 gene product. The thymidine insertion abolished a Ddel restriction site, allowing a rapid test for detection of PKD2 carriers in the family.

Adult↗
PubMed2001

Development of a yeast stop codon assay readily and generally applicable to human genes.

We established a yeast-based method to screen chain-terminating mutations that is readily applicable to any gene of interest. Based on the finding that 18- to 24-base-long homologous sequences are sufficient for gap repair in vivo in yeast, we used a strategy to amplify a test-gene fragment with addition of 24-bp sequences homologous to both cut-ends of a yeast expression vector, pMT18. After co-transformation with the amplified fragment and the linearized pMT18, each yeast (Saccharomyces cerevisiae) cell automatically forms a single-copy circular plasmid (because of CEN/ARS), which expresses a test-gene::ADE2 chimera protein. When the reading frame of the test-gene contains a nonsense or frameshift mutation, truncation of the chimera protein results in lack of ADE2 activity, leading to formation of a red colony. By using a nested polymerase chain reaction using proofreading Pfu polymerase to ensure specificity of the product, the assay achieved a low background (false positivity). We applied the assay to BRCA1, APC, hMSH6, and E-cadherin genes, and successfully detected mutations in mRNA and genomic DNA. Because this method--universal stop codon assay--requires only 4 to 5 days to screen a number of samples for any target gene, it may serve as a high-throughput screening system of general utility for chain-terminating mutations that are most prevalent in human genetic diseases.

Adenomatous Polyposis Coli Protein↗
PubMed1999

Classical LCAT deficiency resulting from a novel homozygous dinucleotide deletion in exon 4 of the human lecithin: cholesterol acyltransferase gene causing a frameshift and stop codon at residue 144.

Lecithin: cholesterolacyltransferase (LCAT) transacylates the fatty acid at the sn-2 position of lecithin to the 3beta-OH group of cholesterol forming lysolecithin and the majority of cholesteryl ester found in plasma. LCAT participates in the reverse cholesterol transport pathway in man where it esterifies tissue-derived cholesterol following efflux from peripheral cells into HDL. Only 38 unique mutations in the human LCAT gene have been reported worldwide. Our French female proband presented with corneal opacity and no detectable plasma LCAT activity using either endogenous or exogenous assays. Her total plasma cholesterol and HDL cholesterol were low (2.34 mmol/l and 0.184 mmol/l, respectively) with a very high cholesterol/cholesteryl ester molar ratio (10.9:1). Plasma triglycerides were 0.470 mmol/l with low apo B (40.5 mg/dl), apo A-I (14.7 mg/dl), apo A-II (6.8 mg/dl) and apo E (2.1 mg/dl) levels. Plasma lipoprotein analysis by ultracentrifugation showed very low HDL concentrations and a characteristic shift of the lipoprotein profile towards larger, less dense particles. No proteinuria, renal dysfunction or signs of atherosclerosis were noted at age 45. Sequence analysis of her LCAT gene showed a novel homozygous TG-deletion at residues 138-139 that resulted in a frameshift causing the generation of a stop codon and premature termination of the LCAT protein at amino acid residue 144. Western blotting of the patient's plasma using a polyclonal IgY primary antibody against human LCAT failed to demonstrate the presence of a truncated LCAT protein. A 53 bp mismatched PCR primer was designed to generate an Fsp 1 restriction site in the wild type sequence of exon 4 where the mutation occurred. The 155 bp PCR product from the wild type allele produced a 103 bp and 52 bp fragment with Fsp 1 and no cleavage products with the mutant allele thus permitting rapid screening for this novel mutation.

Adolescent↗
PubMed1997

Dinucleotide and stop codon frequencies in single-stranded RNA viruses.

To identify potential selection pressures which lead to RNA sequence conservation, we examined the occurrence rates of dinucleotides in 64 single-stranded RNA virus genomes. These viruses may offer a particular insight into these pressures since their RNA-dependent RNA polymerases lack proofreading capability. This potentiates introduction of mutations into their genomes, yet unidentified selection processes conserve the genomes to a large degree. We report a strong inverse correlation between the C+G content and the occurrence of the CpG dinucleotide (r=0.71) in the RNA virus genomes, in contrast to earlier reports (Karlin et al., 1994, Journal of Virology 68, 2889-2897). We also detected significant suppression of UpA, correlating inversely with genomic U+A content. These suppressions are coupled with over-representation of the complementary pair of dinucleotides, CpA and UpG. In addition, we highlight the fact that odds ratios for dinucleotides are not independent variables, a situation apparently not widely appreciated in the literature. This led us to view the over-representation of CpA and UpG as a consequential outcome of UpA and CpG suppression in the virus genomes. Potential factors influencing these disturbances are discussed. In addition, higher than random incidence was observed for 'out-of-frame' stop codons in the viral RNA genomes, with some preferences for individual codons being exhibited by certain virus groups. The UAG codon appeared more common in the +1 frame, the UGA in the -1 frame.

Base Sequence↗
PubMed1995

Selective use of an alternative stop codon and polyadenylation signal within intron sequences leads to a truncated topoisomerase II alpha messenger RNA and protein in human HL-60 leukemia cells selected for resistance to mitoxantrone.

Topoisomerase II alpha is an essential nuclear enzyme involved in DNA replication and a target for many of the clinically useful antineoplastic agents. In a mitoxantrone-selected human leukemia cell line, HL-60/MX2, cellular topoisomerase II (topo II) catalytic activity is decreased, in association with the finding of reduced nuclear topo II alpha and beta protein levels. In addition, HL-60/MX2 cells contain a novel M(r) 160,000 topo II alpha-related protein that localizes predominantly to the cell cytoplasm (W. G. Harker et al., Biochemistry, 30: 9953-9961, 1991). In these studies, we have investigated the molecular mechanisms underlying the altered expression of the topo II alpha protein(s) in these cells. Three topo II alpha mRNAs, 7.2, 6.3, and 4.8 kb, were identified in the HL-60/MX2 cells, with the 6.3 and 4.8 kb transcripts being present in roughly equivalent amounts, while the 7.2-kb mRNA represents < 7% of the total topo II alpha-specific mRNA. Portions of the 3'-coding and 3'-untranslated regions were found to be missing from the 7.2- and 4.8-kb topo II alpha mRNAs by Northern blot analysis. Sequences encoding the 3' regions of the normal and truncated forms of the topo II alpha enzyme were obtained from the HL-60/MX2 cells through the use of a 3'-rapid amplification of cDNA ends strategy. Approximately 1321 nucleotides are missing from the 3'-coding and 3'-untranslated regions of the 4.8-kb mRNA and are replaced by 122 nucleotides that contain an in-frame stop codon and consensus polyadenylation signal. The translation product of the truncated 4388-bp topo II alpha transcript would have a predicted M(r) of 157,850, with 108 COOH-terminal amino acids being replaced by 13 novel residues. Immunoblot analysis confirmed that amino acids in the COOH-terminal region of topo II alpha were missing from the M(r) 160,000 HL-60/MX2 protein, and antisera generated to a synthetic peptide representing the 13 unique amino acids identified a M(r) 160,000 protein in nuclear extracts from these cells. PCR evaluation of the organization of the 3' region of the topo II alpha gene revealed that the 4.8-kb mRNA found in HL-60/MX2 cells diverges from that of the 6.3-kb mRNA at a consensus exon-intron splice donor site. The 122-bp novel nucleotides identified in the truncated transcript appear to originate from an adjacent intron as a result of altered RNA processing. These studies suggest that as a result of the disruption of the carboxy terminus of the topo II alpha protein and the putative nuclear targeting sequences identified therein, cellular localization of the protein is altered, which may confer a growth advantage for the HL-60/MX2 cells in the presence of mitoxantrone.

Amino Acid Sequence↗
PubMed1996

Function of 3' non-coding sequences and stop codon usage in expression of the chloroplast psaB gene in Chlamydomonas reinhardtii.

The rate of mRNA decay is an important step in the control of gene expression in prokaryotes, eukaryotes and cellular organelles. Factors that determine the rate of mRNA decay in chloroplasts are not well understood. Chloroplast mRNAs typically contain an inverted repeat sequence within the 3' untranslated region that can potentially fold into a stem-loop structure. These stem-loop structures have been suggested to stabilize the mRNA by preventing degradation by exonuclease activity, although such a function in vivo has not been clearly established. Secondary structures within the translation reading frame may also determine the inherent stability of an mRNA. To test the function of the inverted repeat structures in chloroplast mRNA stability mutants were constructed in the psaB gene that eliminated the 3' flanking sequences of psaB or extended the open reading frame into the 3' inverted repeat. The mutant psaB genes were introduced into the chloroplast genome of Chlamydomonas reinhardtii. Mutants lacking the 3' stem-loop exhibited a 75% reduction in the level of psaB mRNA. The accumulation of photosystem I complexes was also decreased by a corresponding amount indicating that the mRNA level is limiting to PsaB protein synthesis. Pulse-chase labeling of the mRNA showed that the decay rate of the psaB mRNA was significantly increased demonstrating that the stem-loop structure is required for psaB mRNA stability. When the translation reading frame was extended into the 3' inverted repeat the mRNA level was reduced to only 2% of wild-type indicating that ribosome interaction with stem-loop structures destabilizes chloroplast mRNAs. The non-photosynthetic phenotype of the mutant with an extended reading frame allowed us to test whether infrequently used stop codons (UAG and UGA) can terminate translation in vivo. Both UAG and UGA are able to effectively terminate PsaB synthesis although UGA is never used in any of the Chlamydomonas chloroplast genes that have been sequenced.

Amino Acid Sequence↗
PubMed1996

Semiquantitative assessment of pre-core stop-codon mutant and wildtype hepatitis B virus during the course of chronic hepatitis B using a new PCR-based assay.

In most patients with chronic hepatitis B positive for antibodies (anti-HBe) to HBe antigen (HBeAg), a pre-core mutant hepatitis B virus (HBV) with a point-mutation at nt. 1896 can be isolated. Clinical significance of the mutant virus in chronic hepatitis B is not proven yet, and screening of large numbers of sera during different clinical courses of numerous patients is necessary. We therefore aimed to develop a fast and reliable assay, that allows to discriminate wildtype from nt. 1896 G-->A mutant HBV and to determine the ratio of mutant and wildtype HBV in patients' sera. A mutation specific polymerase chain reaction (ms PCR) with new primers served to distinguish nt. 1896 G-->A mutant from wildtype HBV. This msPCR proved to be more sensitive and specific than similar assays described previously. When compared to a dilution series of a cloned HBV-DNA standard, the amount of wildtype and nt. 1896 G-->A mutant HBV could be determined semiquantitatively. 10(2) to 10(7) copies of each HBV-DNA (equivalent to 10(5) to 10(10) copies of HBV-DNA/ml patients' serum) could be amplified with steadily increasing signals. MsPCR proved to be specific as 10(7) copies did not give an amplification signal if they did not match the respective primer pair used. In a mixed population of mutant and wildtype virus, msPCR allows to detect even a low amount of the minor HBV strain (0.1-0.01%, of the viral population) and to determine the ratio of wildtype and mutant HBV. MsPCR is as fast and convenient to perform as an unmodified PCR. It requires careful performance to avoid contamination but no specific equipment. Clinical usefulness of msPCR was demonstrated when the ratio of wildtype to mutant HBV was determined in 86 sera collected during 3 to 7.5 years follow up of 9 patients suffering from anti-HBe positive chronic hepatitis B. We conclude that this assay conveniently allows to study patients with chronic hepatitis B in order to detect and follow-up the emergence of pre-core stop-codon mutant HBV in correlation to the clinical course.

Chronic Disease↗
PubMed1989

Significance of premature stop codons in env of simian immunodeficiency virus.

The location of the translational termination codon for the transmembrane protein (TMP) varies in three infectious molecular clones of simian immunodeficiency virus from macaques (SIVmac). The SIVmac251 and SIVmac142 infectious clones have premature stop signals that differ in location by one codon; transfection of these DNAs into human HUT-78 cells yielded virus with a truncated TMP (28 to 30 kilodaltons [kDa]). The SIVmac239 infectious clone does not have a premature stop codon in its TMP-coding region. Transfection of HUT-78 cells with this clone initially yielded virus with a full-length TMP (41 kDa). At 20 to 30 days posttransfection, SIVmac239 virus with a 41-kDa TMP gradually disappeared coincident with the emergence of a virus with a 28-kDa TMP. Virus production dramatically increased in parallel with the emergence of a virus with a 28-kDa TMP. Sequence analysis of viral DNAs from these cultures showed that premature stop codons arising by point mutation were responsible for the change in size of the TMP with time. A similar selective pressure for truncated forms of TMP was observed when the SIVmac239 clone was transfected into human peripheral blood lymphocytes (PBL). In contrast, no such selective pressure was observed in macaque PBL. When the SIVmac239 clone was transfected into macaque PBL and the resultant virus was serially passaged in macaque PBL, the virus replicated very well and maintained a 41-kDa TMP for 80 days in culture. Macaque monkeys were infected with SIVmac239 having a 28-kDa TMP; virus subsequently recovered from T4-enriched lymphocytes of peripheral blood showed only the 41-kDa form of TMP. These results indicate that the natural form of TMP in SIVmac is the full-length 41-kDa TMP, just as in human immunodeficiency virus type 1. Viruses with truncated forms of TMP appear to result from mutation and selection during propagation in unnatural human cells.

Amino Acid Sequence↗
PubMed2002

Stop codon insertion restores the particle formation ability of hepatitis B virus core-hantavirus nucleocapsid protein fusions.

In recent years, epitopes of various origin have been inserted into the core protein of hepatitis B virus (HBc), allowing the formation of chimeric HBc particles. Although the C-terminus of a C-terminally truncated HBc (HBc) tolerates the insertion of extended foreign sequences, the insertion capacity is still a limiting factor for the construction of multivalent vaccines. Previously, we described a new system to generate HBc mosaic particles based on a read-through mechanism in an Escherichia coli suppressor strain [J Gen Virol 1997;78:2049-2053]. Those mosaic particles allowed the insertion of a 114-amino acid (aa)-long segment of a Puumala hantavirus (PUUV) nucleocapsid (N) protein. To study the value and the potential limitations of the mosaic approach in more detail, we investigated the assembly capacity of 'non-mosaic' HBc fusion proteins and the corresponding mosaic constructs carrying 94, 213 and 433 aa of the hantaviral N protein. Whereas the fusion proteins carrying 94, 114, 213 or 433 aa were not assembled into HBc particles, or only at a low yield, the insertion of a stop codon-bearing linker restored the ability to form particles with 94, 114 and 213 foreign aa. The mosaic particles formed exhibited PUUV-N protein antigenicity. Immunization of BALB/c mice with these mosaic particles carrying PUUV-N protein aa 1-114, aa 1-213 and aa 340-433, respectively, induced HBc-specific antibodies, whereas PUUV-N protein-specific antibodies were detected only in mice immunized with particles carrying N-terminal aa 1-114 or aa 1-213 of the N protein. Both the anti-HBc and anti-PUUV antibody responses were IgG1 dominated. In conclusion, stop codon suppression allows the formation of mosaic core particles carrying large-sized and 'problematic', e.g. hydrophobic, hantavirus sequences.

Animals↗
PubMed1991

RNA editing makes mistakes in plant mitochondria: editing loses sense in transcripts of a rps19 pseudogene and in creating stop codons in coxI and rps3 mRNAs of Oenothera.

An intact gene for the ribosomal protein S19 (rps19) is absent from Oenothera mitochondria. The conserved rps19 reading frame found in the mitochondrial genome is interrupted by a termination codon. This rps19 pseudogene is cotranscribed with the downstream rps3 gene and is edited on both sides of the translational stop. Editing, however, changes the amino acid sequence at positions that were well conserved before editing. Other strange editings create translational stops in open reading frames coding for functional proteins. In coxI and rps3 mRNAs CGA codons are edited to UGA stop codons only five and three codons, respectively, downstream to the initiation codon. These aberrant editings in essential open reading frames and in the rps19 pseudogene appear to have been shifted to these positions from other editing sites. These observations suggest a requirement for a continuous evolutionary constraint on the editing specificities in plant mitochondria.

Amino Acid Sequence↗