Mechanism of Splicing

Mechanism of Splicing


Mechanism of Splicing

  • The binding of snRNP brings the sequences of the neighboring exons into the correct alignment for splicing
  • Splicing occurs in several steps and is catalyzed by small nuclear ribonucleoproteins (snRNPs, commonly pronounced “snurps”).
  • It start  with a cut  in  the  5′ splice  donor  site.

 

  • Introns are removed from primary transcripts by cleavage at conserved sequences called splice sites. These sites are found at the 5′ and 3′ ends of introns.
  • The cut end then attaches to the conserved branch point region downstream through pairing of guanine and adenine nucleotides from the 5′ end and the branch point to form a looped structure known as a lariat
  • The bonding of the guanine and adenine bases takes place via a chemical reaction known as transesterification
  • The guanine residue (introns) is thus cleaved from the RNA strand and forms a new bond with the adenine.
  • an OH group at the 3′ end of the exon attacks the phosphodiester bond at the 3′ splice site.
  • The adjoining exons are covalently bound, and the resulting lariat is released with U2, U5, and U6 bound to it.
  • After introns have been removed and exons joined, the mature mRNA molecules leave the nucleus and pass into the cytosol through pores in the nuclear membrane.
  • Self Splicing :Certain hnRNA itself has splicing activity Because of Ribozyme activity.
  • mutations that cause the incorrect splicing of p-globin mRNA are responsible for some cases of β-thalassemia.
  • Selective Splicing- selective inclusion or exclusion of exons
  • Altemative 5’donor site- S’ donor site of certain exons is changed.
  • Alternative 3′ acceptor site- 3′ acceptor site of certain exons is changed.
  • Alternative Polyadenylation site-Different site is used for Poly-adenylation.

Exam Important

  • Introns are removed from primary transcripts by cleavage at conserved sequences called splice sites. These sites are found at the 5′ and 3′ ends of introns.
  • The cut end then attaches to the conserved branch point region downstream through pairing of guanine and adenine nucleotides from the 5′ end and the branch point to form a looped structure known as a lariat
  • The bonding of the guanine and adenine bases takes place via a chemical reaction known as transesterification
  • The guanine residue (introns) is thus cleaved from the RNA strand and forms a new bond with the adenine.
  • an OH group at the 3′ end of the exon attacks the phosphodiester bond at the 3′ splice site.
  • The adjoining exons are covalently bound, and the resulting lariat is released with U2, U5, and U6 bound to it.
  • After introns have been removed and exons joined, the mature mRNA molecules leave the nucleus and pass into the cytosol through pores in the nuclear membrane.
  • Self Splicing :Certain hnRNA itself has splicing activity Because of Ribozyme activity.
  • mutations that cause the incorrect splicing of p-globin mRNA are responsible for some cases of β-thalassemia.
  • Selective Splicing- selective inclusion or exclusion of exons
  • Altemative 5’donor site- S’ donor site of certain exons is changed.
  • Alternative 3′ acceptor site- 3′ acceptor site of certain exons is changed.
  • Alternative Polyadenylation site-Different site is used for Poly-adenylation
Don’t Forget to Solve all the previous Year Question asked on Mechanism of Splicing
Click Here to Start Quiz

Module Below Start Quiz

Leave a Reply

%d bloggers like this:
Malcare WordPress Security