RNA editing Flashcards
where is apoB100 synthesized and used for?
synthesized in the liver and is necessary for the assembly of VLDL and transport of TAG
where is apoB48 synthesized and used for?
synthesized by the intestine and is essential for chylomicron formation and absorption and transport of dietary cholesterol and TAG
what are the reasons for possible resemblance of apoB100 and apoB48?
apoB100 and apoB48 could be encoded by separate genes
apoB48 could be produced from apoB100 by posttranslational proteolytic processing
Differential processing of a primary nuclear RNA transcript could produce 2 tissue specific mRNAs coding for each
what was the findings of the apoB experiment?
They isolated mRNA from intestinal cells and converted the apoB48 mRNA into DNA copies (cDNA), cloned the cDNA and prepared and sequenced ten different cDNA clones
All 10 cDNA closes had an in frame stop codon after codon 2152. In contrast, all 5 apoB100 liver cDNA sequences abd all 3 published genomic DNA sequences had glutamine codon at the same position
what is southern blotting?
Separate DNA fragments by agarose gel electrophoresis and denature them under alkaline conditions. Transfer the ssDNA to a membrane and probe them
what were the probes used?
BGLN adn BSTOP
what does BGLN detect?
detects complementary sequences only in liver-derived tissue and not in intestinal
what does BSTOP detect?
detects complementary sequences only in intestinal and not the liver.
what does genomic, intestional and liver encode?
Genomic DNA - encodes only a gln codon
Liver mRNA contains a gln codon
Intestinal mRNA contains a stop codon
what is the characteristics of the deamination reaction?
In the small intestine, cytidine in the mRNA for human apoB is deaminated to uridine. This changes a CAA (gln) to a UAA (stop) which leads to synthesis of a shorter protein - apoB48
what is the adenosine to inosine mutation?
Inosine was found in the anticodon of the first tRNA that was sequences
Inosine us interpreted as guanosine, so edits in a coding region could change the final protein sequence
This is catalyzed by the ADAR enzyme
what does the adenosine to inosine mutation cause?
dyschromatosis symmetrica hereditaria
where and when does nucleoside modification occur?
In tRNA occurs after transcription
what are the 2 types of RNA editing?
Cytidine insertion in slime molds
Uridine insertion/deletion in trypanosomes - parasites that cause chagas disease and african sleeping sickness
what do guide RNAs do?
bind to mRNAs and define insertion and deletion locations. They base pair with mRNA and if a mismatch occurs then an endonuclease cuts the mRNA there
