Related Experiment Videos
The poly(A)-limiting element is a conserved cis-acting sequence that regulates poly(A) tail length on nuclear
H Gu1, J Das Gupta, D R Schoenberg
1Department of Pharmacology, Ohio State Biochemistry Program, and the Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA.
Abstract:
Most vertebrate mRNAs exit the nucleus with a 200+-residue poly(A) tail and are deadenylated to yield heterogeneous polymers of 50-200 adenosine residues on any given mRNA. We previously reported that Xenopus albumin mRNA and pre-mRNA have an unusually short, discrete 17-residue poly(A) tail and showed that regulation of poly(A) length is controlled independently by two cis-acting poly(A)-limiting elements (PLE A and PLE B) located in the terminal exon. The present study sought to determine the generality of this regulatory mechanism. Transferrin mRNA also has a discrete <20-nt poly(A) tail, and deletion mapping experiments identified an element homologous to the albumin gene PLE B within the terminal exon of the transferrin gene that conferred poly(A) length regulation on a globin reporter mRNA. Based on this similarity the PLE B sequence was used in a database search to identify candidate mRNA targets for regulated polyadenylation. Of the several hundred sequences identified in this manner we focused on HIV-EP2/Schnurri-2, a member of a family of genes encoding related zinc finger transcription factors. A striking feature of the PLE-like element in these genes is its location 10-33 bp upstream of the translation stop codon. We demonstrate that HIV-EP2 mRNA has a <20-nt poly(A) tail, for which the identified PLE-like sequence is responsible. These results indicate that the presence of a PLE can predict mRNAs with <20-nt poly(A) tails, and that nuclear regulation of poly(A) tail length is a feature of many mRNAs.
Insights
This study reveals that specific DNA sequences, known as poly(A)-limiting elements (PLEs), control short poly(A) tail lengths in mRNAs like transferrin and HIV-EP2. This mechanism, previously observed in Xenopus, is more widespread than initially thought.
Area of Science:
- Molecular Biology
- Gene Regulation
- RNA Processing
Background:
- Vertebrate mRNAs typically have long poly(A) tails (50-200 nt) after deadenylation.
- Previously, Xenopus albumin mRNA was found to have a short, discrete 17-nt poly(A) tail regulated by poly(A)-limiting elements (PLEs).
Purpose of the Study:
- To investigate the generality of the PLE-mediated poly(A) tail length regulation mechanism.
- To identify other mRNAs regulated by this mechanism and the responsible cis-acting elements.
Main Methods:
- Deletion mapping experiments were used to identify regulatory elements in transferrin mRNA.
- Database searches utilizing the PLE B sequence identified candidate mRNA targets.
- Reporter assays and sequence analysis were performed on HIV-EP2/Schnurri-2.
Main Results:
- Transferrin mRNA also possesses a discrete poly(A) tail (<20 nt) regulated by a PLE B-homologous element.
- A PLE-like element was identified upstream of the stop codon in HIV-EP2/Schnurri-2, responsible for its <20-nt poly(A) tail.
- The presence of a PLE sequence can predict mRNAs with short poly(A) tails.
Conclusions:
- Nuclear regulation of poly(A) tail length by PLEs is a common mechanism across various mRNAs.
- This regulatory mechanism extends beyond Xenopus and impacts genes like transferrin and HIV-EP2.