Rho has an N-terminal, RNA-binding domain and a C-terminal ATPase domain. A hexamer in the form of a gapped ring binds RNA along the exterior of the N-terminal domains. The 5’ end of the RNA is bound by a secondary binding site in the interior of the hexamer.

TLS Online TPP Program

#Id: 1982

#Unit 3. Fundamental Processes

After transcription initiation, Pol II is paused 30 nucleotides downstream from the initiation site, recruits of the capping enzymes.

TLS Online TPP Program

#Id: 1983

#Unit 3. Fundamental Processes

Capping is done by a dimeric nuclear enzyme which has two subunits and three functions

1. Guanylyl-transferase (GT)

2. Methyltransferase (MT)

TLS Online TPP Program

#Id: 1984

#Unit 3. Fundamental Processes

Structure of cap is

   

TLS Online TPP Program

#Id: 1985

#Unit 3. Fundamental Processes

Binding of the capping enzyme to the TFIIH mediated serine 5–phosphorylated CTD stimulates the activity of the enzyme.

TLS Online TPP Program

#Id: 1986

#Unit 3. Fundamental Processes

RNA polymerases I or III do not have a CTD so no capping is stimulated

TLS Online TPP Program

#Id: 1987

#Unit 3. Fundamental Processes

The 5’ cap of most mRNA is monomethylated, but some small noncoding RNAs are trimethylated.