Allelopathy- Asymmetric competition can be observed between plants, where one species produces and secretes chemicals from its roots that inhibit the growth of another species.

TLS Online TPP Program

#Id: 1992

#Unit 3. Fundamental Processes

Binding of polyadenylation factors takes place when CTD Ser2 phosphorylated.

TLS Online TPP Program

#Id: 1993

#Unit 3. Fundamental Processes

Phosphorylation on Ser2 by P-TEFb activates elongation, splicing and polyadenylation

TLS Online TPP Program

#Id: 1994

#Unit 3. Fundamental Processes

The polyadenylation site has two cis-acting signals: 

An upstream AAUAAA motif, which is usually located 11 to 30 nucleotides from the site  A downstream U-rich or GU-rich element.

TLS Online TPP Program

#Id: 1995

#Unit 3. Fundamental Processes

The AAUAAA is needed for cleavage and polyadenylation because deletion or mutation of the AAUAAA hexamer prevents generation of the polyadenylated 3’ end

TLS Online TPP Program

#Id: 1996

#Unit 3. Fundamental Processes

AAUAAA motif- CPSF CPSF 73 (CF1 & CFII)- Poly A site GU element- CstF

TLS Online TPP Program

#Id: 1997

#Unit 3. Fundamental Processes

The polyadenylation reaction passes through two stages. 

First, a rather short oligo(A) sequence (10 residues) is added to the 3’ end. This reaction is absolutely dependent on the AAUAAA sequence and poly(A) polymerase performs it under the direction of the specificity factor. 

In the second phase, the nuclear poly(A) binding protein (PABP II) binds the oligo(A) tail to allow extension of the poly(A) tail to the full 200 residue length.