During first cleavage, the metaphase plate is closer to the posterior, & fertilized egg is divided into two cells:

one having the anterior PARs (PAR-6 and PAR-3)

one having the posterior PARs (PAR-2 and PAR-1)

TLS Online TPP Program

#Id: 1989

#Unit 3. Fundamental Processes

SL RNA (Trans-splicing) carries a trimethylated cap, which is recognized by the variant cap-binding factor eIF4E to facilitate translation.

TLS Online TPP Program

#Id: 1990

#Unit 3. Fundamental Processes

The sequence AAUAAA (hexamer) is a signal for cleavage to generate a 3’ end of mRNA that is polyadenylated.

TLS Online TPP Program

#Id: 1991

#Unit 3. Fundamental Processes

Polyadenylation requires a protein complex that contains a specificity factor, an endonuclease, and poly(A) polymerase.

 

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.