Post-transcriptional polyadenylation site cleavage maintains 3'-end processing upon DNA damage

Area of Science:

• Molecular Biology
• Gene Expression Regulation
• DNA Damage Response

Background:

• Polyadenylation signal (PAS) recognition is typically coupled to transcription termination on chromatin-bound pre-mRNAs.
• Some pre-mRNAs undergo post-transcriptional 3'-end processing via co-transcriptional cleavage (CoTC), releasing them from chromatin for nucleoplasmic PAS cleavage.
• DNA-damaging agents typically inhibit co-transcriptional 3'-end processing, but compensatory mechanisms exist for specific pre-mRNAs, including those in the DNA damage response pathway.

Purpose of the Study:

• To investigate the role of CoTC in the 3'-end processing of p53 pre-mRNA following DNA damage.
• To identify other pre-mRNAs that utilize post-transcriptional processing to evade DNA damage-induced 3'-end processing inhibition.
• To understand how specific pre-mRNAs maintain 3'-end processing during UV-induced DNA damage.

Main Methods:

• Analysis of p53 polyadenylation site cleavage, including engineered deletion of the p53 CoTC site.
• Measurement of p53 and p21 mRNA and protein levels.
• Assessment of cell cycle progression after UV-induced DNA damage.
• Transcriptome-wide analysis of polyadenylation site (PAS) cleavage in response to UV irradiation.

Main Results:

• Cleavage at the p53 polyadenylation site occurs partially post-transcriptionally after a CoTC event.
• Deletion of the p53 CoTC site impairs p53 3'-end processing, reduces p53 and p21 levels, and alters cell cycle progression post-UV.
• Transcriptome-wide analysis identified additional pre-mRNAs with maintained, post-transcriptional PAS cleavage following UV irradiation.

Conclusions:

• Co-transcriptional cleavage (CoTC) followed by nucleoplasmic PAS cleavage allows specific pre-mRNAs to escape 3'-end processing inhibition caused by UV-induced DNA damage.
• This mechanism is crucial for maintaining the expression of proteins involved in the DNA damage response, such as p53.
• The findings reveal a conserved strategy for ensuring gene expression resilience under genotoxic stress.