[Canonical and noncanonical RNA polyadenylation].

Area of Science:

• Molecular Biology
• Gene Expression Regulation
• RNA Processing

Background:

• Polyadenylation is the addition of adenosine nucleotides to the 3'-end of RNA, forming a poly(A) tail.
• This process is crucial for mRNA stability and translation efficiency.
• Canonical polyadenylation involves RNA polymerase II and specific sequence signals like AAUAAA.

Purpose of the Study:

• To review the classical mRNA 3'-end formation and polyadenylation.
• To explore the less-understood polyadenylation of RNA synthesized by RNA polymerase III.
• To discuss AAUAAA-independent polyadenylation by TRAMP enzymes for RNA degradation.

Main Methods:

• Literature review of established and recent findings on polyadenylation.
• Analysis of RNA polymerase II and III functions in RNA processing.
• Examination of noncanonical polyadenylation mechanisms.

Main Results:

• RNA polymerase II-mediated polyadenylation requires the AAUAAA signal and enhances mRNA lifetime and translation.
• RNA polymerase III can perform AAUAAA-dependent polyadenylation on specific RNAs (SINEs).
• TRAMP poly(A)-polymerases (Trf4, Trf5) mediate AAUAAA-independent polyadenylation for RNA degradation.

Conclusions:

• Polyadenylation is a complex process with diverse mechanisms beyond canonical mRNA processing.
• RNA polymerase III and TRAMP enzymes represent alternative pathways with distinct regulatory roles.
• Understanding these varied polyadenylation strategies is key to comprehending RNA metabolism and quality control.