mRNA Processing in Eukaryotes

mRNAs are

capped, spliced, and poly-adenylated in eukaryotes

Often presented as separate from transcription

• transcription creates the “pre-mRNA)

• processing occurs separately

In fact, processing occurs co-transcriptionally

• the “pre-mRNA” as a finished product is imaginary

The CTD of RNA Pol II 1.1

acts as a scaffold for mRNA processing enzymes and complexes

The CTD of RNA Pol II 1.2, During initiation,

Ser5s in the CTD are phosphorylated and capping proteins bind to the CTD

The CTD of RNA Pol II 1.3, During elongation,

Ser5s and Ser2s in CTD are phosphorylated

splicing complexes bind

The CTD of RNA Pol II 1.4, Near termination,

Ser5s are partially dephosphorylated

CPSF and CstF bind

The CTD of RNA Pol II (1)

acts as a scaffold for mRNA processing enzymes and complexes

During initiation, Ser5s in the CTD are phosphorylated and capping proteins bind to the CTD

During elongation, Ser5s and Ser2s in the CTD are phosphorylated and splicing complexes bind

Near termination, Ser5s are partially dephosphorylated and CPSF and CstF bind

shortly after initiation,

Shortly after initiation, the 5’ end of the mRNA is capped by capping proteins

During elongation

splicesosomes remove introns

At the termination sequence,

CPSF and CstF cleave the mRNA, creating the 3’ end of the functional mRNA

this is an important step before polyadenylation

The CTD of RNA Pol II (2)

Shortly after initiation, the 5’ end of the mRNA is capped by capping proteins

During elongation, splicesosomes remove introns

At the termination sequence, CPSF and CstF cleave the mRNA, creating the 3’ end of the functional mRNA

this is an important step before polyadenylation

mRNAs are capped, spliced, and poly-adenylated in eukaryotes (2)

•Processing occurs co-transcriptionally

•Processing enzymes and complexes associate with RNA Pol II during transcription

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