The CTD interacting domain of Pcf 11 in complex with a CTD peptide. Conserved surface residues are colored in green

RNA processing at the 3'-end

RNA processing at the 3'-end

Eucaryotic mRNA undergoes several post-transcriptional processing steps before it becomes exported from the nucleus. In the first step the cap structure is added to the 5'-end of the nascent RNA. During RNA polymerase II (Pol II) transcription elongation, introns are removed mainly by the splicosome. And concurrently with transcription termination, the pre-mRNA becomes chopped from the transcription machinery and in most cases a poly(A) tail is added to the 3'-end of the RNA.

These post-transcriptional processing events are interlinked with the Pol II. The major platform for coupling is the mobile carboxy-terminal domain (CTD) of the largest subunit Rpb1 of Pol II. The CTD contains multiple copy numbers of a highly repetitive amino acid sequence (26 repeats in yeast).

During the transcription cycle, the CTD becomes phosphorylated and dephosphorylated. This dynamic phosphorylation-pattern triggers factor recruitment to the transcription machinery. Recently, we could shade light on how the cleavage/polyadenylation factor Pcf11 recognizes the phosphorylated CTD. Pcf11 binds to the CTD using a highly conserved groove in the CTD-interacting domain (CID).

In yeast the mRNA cleavage and polyadenylation machinery contains two large multisubunit complexes, the cleavage factor I and the cleavage / polyadenylation factor, respectively. Both factors recognize the signaling sequences for RNA cleavage.

Additionally, the cleavage / polyadenylation factor is proposed to contain the endonuclease that cuts the nascent RNA. Both factors are large multimeric complexes and their atomic structures are still enigmatic.

Go to Editor View