Biomedical subjects

Christine B Anderson

Publications and source records attributed to Christine B Anderson.

6 recordsLinked to original sources

PubMed2006

Antisense-induced ribosomal frameshifting.

Programmed ribosomal frameshifting provides a mechanism to decode information located in two overlapping reading frames by diverting a proportion of translating ribosomes into a second open reading frame (ORF). The result is the production of two proteins: the product of standard translation from ORF1 and an ORF1-ORF2 fusion protein. Such programmed frameshifting is commonly utilized as a gene expression mechanism in viruses that infect eukaryotic cells and in a subset of cellular genes. RNA secondary structures, consisting of pseudoknots or stem-loops, located downstream of the shift site often act as cis-stimulators of frameshifting. Here, we demonstrate for the first time that antisense oligonucleotides can functionally mimic these RNA structures to induce +1 ribosomal frameshifting when annealed downstream of the frameshift site, UCC UGA. Antisense-induced shifting of the ribosome into the +1 reading frame is highly efficient in both rabbit reticulocyte lysate translation reactions and in cultured mammalian cells. The efficiency of antisense-induced frameshifting at this site is responsive to the sequence context 5' of the shift site and to polyamine levels.

Animals↗

PubMed2005

Recoding elements located adjacent to a subset of eukaryal selenocysteine-specifying UGA codons.

Incorporation of the 21st amino acid, selenocysteine, into proteins is specified in all three domains of life by dynamic translational redefinition of UGA codons. In eukarya and archaea, selenocysteine insertion requires a cis-acting selenocysteine insertion sequence (SECIS) usually located in the 3'UTR of selenoprotein mRNAs. Here we present comparative sequence analysis and experimental data supporting the presence of a second stop codon redefinition element located adjacent to a selenocysteine-encoding UGA codon in the eukaryal gene, SEPN1. This element is sufficient to stimulate high-level (6%) translational redefinition of the SEPN1 UGA codon in human cells. Readthrough levels further increased to 12% when tested in the presence of the SEPN1 3'UTR SECIS. Directed mutagenesis and phylogeny of the sequence context strongly supports the importance of a stem loop starting six nucleotides 3' of the UGA codon. Sequences capable of forming strong RNA structures were also identified 3' adjacent to, or near, selenocysteine-encoding UGA codons in the Sps2, SelH, SelO, and SelT selenoprotein genes.

Animals↗

PubMed2005

Programmed ribosomal frameshifting in decoding the SARS-CoV genome.

Programmed ribosomal frameshifting is an essential mechanism used for the expression of orf1b in coronaviruses. Comparative analysis of the frameshift region reveals a universal shift site U_UUA_AAC, followed by a predicted downstream RNA structure in the form of either a pseudoknot or kissing stem loops. Frameshifting in SARS-CoV has been characterized in cultured mammalian cells using a dual luciferase reporter system and mass spectrometry. Mutagenic analysis of the SARS-CoV shift site and mass spectrometry of an affinity tagged frameshift product confirmed tandem tRNA slippage on the sequence U_UUA_AAC. Analysis of the downstream pseudoknot stimulator of frameshifting in SARS-CoV shows that a proposed RNA secondary structure in loop II and two unpaired nucleotides at the stem I-stem II junction in SARS-CoV are important for frameshift stimulation. These results demonstrate key sequences required for efficient frameshifting, and the utility of mass spectrometry to study ribosomal frameshifting.

Base Sequence↗

PubMed2004

Identification of a new antizyme mRNA +1 frameshifting stimulatory pseudoknot in a subset of diverse invertebrates and its apparent absence in intermediate species.

The expression of eukaryotic antizyme genes requires +1 translational frameshifting. The frameshift in decoding most vertebrate antizyme mRNAs is stimulated by an RNA pseudoknot 3' of the frameshift site. Although the frameshifting event itself is conserved in a wide variety of organisms from yeast to mammals, until recently no corresponding 3' RNA pseudoknot was known in invertebrate antizyme mRNAs. A pseudoknot, different in structure and origin from its vertebrate counterparts, is now shown to be encoded by the antizyme genes of distantly related invertebrates. Identification of the 3' frameshifting stimulator in intermediate species or other invertebrates remains unresolved.

Animals↗

PubMed2004

Readthrough of dystrophin stop codon mutations induced by aminoglycosides.

We report the translational readthrough levels induced by the aminoglycosides gentamicin, amikacin, tobramycin, and paromomycin for eight premature stop codon mutations identified in Duchenne's and Becker's muscular dystrophy patients. In a transient transfection reporter assay, aminoglycoside treatment results show that one stop codon mutation is suppressed significantly better (up to 10% stop codon readthrough) than the others; five show lower but statistically significant suppression (< 2% stop codon readthrough); and two appear refractory to aminoglycoside treatment. Readthrough levels do not substantially vary between different sources of gentamicin, and, for this set of mutations, the efficiency of termination at the premature stop codon mutation does not appear to correlate with disease severity.

Aminoglycosides↗

PubMed2002

Subcellular distribution of Wnt pathway proteins in normal and neoplastic colon.

Mutations in the APC tumor suppressor gene are present in approximately 85% of colorectal tumors and are thought to contribute early in the process of tumorigenesis. The truncated protein resulting from most APC mutations can lead to elevated beta-catenin levels in colon tumor cells. APC and associated proteins thus form a beta-catenin regulatory complex, with axin playing a key role. Although cell culture studies have revealed intriguing aspects of this complex, little characterization has been done in human colonocytes, the target tissue of colon carcinogenesis. The present study of intact human colon crypts, adenomatous polyps, and adenocarcinomas focuses on subcellular localization of some key elements of the complex: beta-catenin, APC, axin, and axin2. We examined endogenous protein localization within the framework of three-dimensional tissue architecture by using laser scanning confocal microscopy, and immunofluorescence staining of whole-mount fixed tissue from more than 50 patients. Expression patterns suggest that APC and axin colocalize in the nucleus and at lateral cell borders, and show that axin2 is limited to the nucleus. Altered nuclear expression of axin seen in colon polyps and carcinomas may be a consequence of the loss of full-length APC and the advent of nuclear beta-catenin. The observation of nuclear beta-catenin in fewer than half of carcinoma images and only rarely in polyps indicates that nuclear translocation of beta-catenin may not be an immediate consequence of the loss of APC.

Adenomatous Polyps↗