RNA production and processing Flashcards
Eukaryotes: RNA polymerase I
Makes rRNA (ribosomal RNA that is needed for protein synthesis. two subunits which are involved in forming peptide bonds between amino acids which are
RNA polymerase II
makes mRNA which is a transcription of DNA. pre mRNA is made and then spliced together to make mature mRNA which is moved to the ribosomes for translation. Death cap (Amanita phalloides) mushroom inhibits this.
RNA polymerase III
makes tRNA (transfer RNA) needed for protein synthesis for individual codons. brings individual amino acids to ribsome for protein synthesis.
In prokaryotes?
Only one multiunit RNA polymerase is used to created all three types of RNA.
Rifampicin is used to disrupt prokaryotes RNA.
Actiomycin D inhibits RNA polymerase in both pro and eu
Initial transciption product of DNA is called
Heterogenous nuclear RNA, this is modified to mRNA
RNA processing
hnRNA is capped at 5’ end with Gppp (7-methylguanosine cap)
It is then polyadenylation of 3’ (200As)
Spliced out of introns.
hn RNA –> capped, tailed and then spliced to make mRNA.
Splicing is a process where by pre mRNA is…
Combined with small nuclear RiboNuclearProteins forming a spliceome,
Formed into a lariat knot, the lariat is released removing the intron.
Problems in splicing
Antibodies to snRNPs (anti smith antibodies) are present in SLE.
Antibodies to U1 RNP are associated with Mixed connective tissue disease.
Abnormal splicing can occur (beta thalassemia)
Introns are
non coding segments of DNA which are not expressed
Exons are
Coding segments of DNA that are expressed as proteins.
Different exons can be combined in alternative patterns to form a huge number of different proteins.
What is tRNA and its structure
RNA responsible for transporting individual amino acids into ribosomes for protein synthesis.
Has a clover leaf structure.
Contains an anticodon (Anti codon of the mRNA codon for specific amino acid)
T-arm is necessary for tRNA-ribosome binding.
D-arm with dihydrouracil residues for aminoacyl-tRNA synthetase recognition.
5’-CCA-3’ acceptor stem where the amino acid binds.
What enzyme binds the amino acid to the tRNA acceptor arm?
Aminoacyl-tRNA synthetase binds amino acid to the CCA-3’ acceptor site.
What is a wobble?
accurate amino acid pairing requires the first two nucleotide positions. The third position is a wobble position where a different nucleotide may code for the same amino acid.
