TR3.5

mRNA preprocessing

Houjun Liu 2021-09-27 Mon 12:00

1 mRNA Pre-Processing

Between Promoter and Terminator, Exon and Intron alternate. Exon is coding, whereas Intron is non-coding and works as metadata.

After reading the intron, they are spliced out during mRNA processing => done by the "splicesome". The mRNA, after splicing, is "capped and tailed" to mark pre-processing completion, at which point they leave the nucleus + go to the ribosome.

1.1 Slicing out the non-coding parts

  • Begin by assembling helper proteins at intron-exon borders => "slicing factors"
  • Other helping factor proteins come together and form the "splicesome" to do the splicing
  • Splicesome splices by bringing exon ends together
  • After it's done, the splicesome disintergrates

1.2 Marking for Maturity

After the slicing is done, each finished mRNA is marked for maturity:

  • 3' end => AAAAAA tail (using poly-adenine tailing enzyme)
  • 5' end => GGGGGG cap (using guanine-capping enzyme)