post-transcriptional regulation

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Created by
Christian

Cards (19)

  • mRNA splicing is the removal of introns from pre-mRNA and the joining of exons to make mature mRNA
  • The splicesome is composed of non-coding RNAs and several proteins and binds to intron-exon junctions
  • Introns are looped out of the pre-mRNA to form the lariat structure before being clipped at each exon boundary and released. Adjacent exons then come together
  • In alternative splicing, different splicing combinations generate multiple different mRNAs from a gene which will synthesize related protein products called isoforms
  • microRNAs are transcribed by RNA pol II
  • small interfering RNAs are transcribed by RNA pol II or can be of foreign origin
  • Dicer Rnase cleaves miRNA and siRNA precursors to 21-23 bp double-stranded RNAs which are now substrates of RISC
  • RISC stands for RNA Induced Silencing Complex
  • RISC unwinds one of the RNA strans which attracts binding of complementary mRNA, repressing gene expression by interfering with translation initiation and inducing mRNA degredation
  • Stability of mRNA depends on the presence of the 5-cap and length of poly-A tail
  • Splicing generates UTRs and open reading frame consisting of a continuous stretch of codons
  • mRNA is exported from the nucleus into the cytoplasm to associate with ribosomes
  • Post-transcriptional processing includes the addition of the 5-cap and poly-A tail and splicing
  • The 5-cap is a modified guanosine triphosphate added to the 5 end of the mRNA and acts as a ribosome binding site as well as protects mRNA from degradation
  • The poly-A tail is a long string os adenine nucleotides added to the 3 end that prevents mRNA degradation and increases translation efficiency
  • The UTRs are the 5 and 3 ends of mRNAs that are not translated
  • 5 and 3 UTRs regulate mRNA stability and translational efficiency
  • The 5-UTR contains a ribosome binding site that functions in translational initiation. This is called a Shine Dalgarno sequence in prokaryotes and a Kozak box sequence in eukaryotes
  • The open reading frame is the region of mRNA that is translated and includes the stop and start codons at the borders