Uridylation by TUT4 and TUT7 marks mRNA for degradation

Area of Science:

• Molecular Biology
• RNA Biology
• Gene Expression Regulation

Background:

• Uridylation is a common post-transcriptional modification of mRNAs.
• The enzymes and regulatory mechanisms governing mRNA uridylation are largely unknown.
• The biological significance of mRNA uridylation in cellular processes is poorly understood.

Purpose of the Study:

• To identify the specific enzymes responsible for mRNA uridylation.
• To elucidate the mechanism and regulation of mRNA uridylation.
• To determine the functional role of mRNA uridylation in mRNA decay and microRNA targeting.

Main Methods:

• TAIL-seq (5' and 3' rapid amplification of cDNA ends) was employed to profile RNA modifications.
• In vitro biochemical assays were used to test enzyme activity and substrate specificity.
• CRISPR/Cas9-mediated gene depletion was utilized to assess the in vivo function of identified enzymes.
• Analysis of mRNA decay rates and microRNA target stability was performed.

Main Results:

• TUT4 (ZCCHC11) and TUT7 (ZCCHC6) were identified as the primary mRNA uridylation enzymes.
• Uridylation predominantly occurs on deadenylated mRNAs with short poly(A) tails, a process antagonized by PABPC1.
• Depletion of TUT4/7 leads to loss of oligo-uridylation and extended mRNA half-lives.
• microRNA-induced uridylation is dependent on TUT4/7 and promotes target mRNA decay.

Conclusions:

• TUT4/7 enzymes selectively uridylate deadenylated mRNAs, marking them for degradation.
• The oligo-U-tail serves as a critical molecular signal for global mRNA decay.
• This mechanism plays a significant role in microRNA-mediated gene silencing and post-transcriptional regulation.