mRNA Polyadenylation mRNA processing in eukaryotes

Picture 1

Picture 2

Cleavage proteins 1.1

associate with Pol II during late stages of transcription

Cleavage proteins 1.2

CPSF and CstF travel with the Pol II CTD

Cleavage proteins 1.3

CPSF and CstF are transferred to the RNA

Cleavage proteins

1. associate with Pol II during late stages of transcription

2. CPSF and CstF travel with the Pol II CTD

3. CPSF and CstF are transferred to the RNA

mRNA is cleaved 1.0, where is it cleaved

at termination sequence, then 3’ end is polyadenylated

mRNA is cleaved 1.1

RNA is cleaved

mRNA is cleaved 1.2

poly A polymerase (PAP) adds As (~200 As)

mRNA is cleaved 1.3

poly A binding protein binds—more polyA-binding proteins leads to a longer polyA tail (usually ~200As)

mRNA is cleaved

at termination sequence, then 3’ end is polyadenylated

1. RNA is cleaved

2. poly A polymerase (PAP) adds As (~200 As)

3. poly A binding protein binds—more polyA-binding proteins leads to a longer polyA tail (usually ~200As)

Functions of polyadenylation

1. Protects against nucleases

2. Facilitates mRNA export from the nucleus

3. facilitates translation