Regulation of Translational Efficiency by Disparate 5′-UTRs of PPARγ Splice Variants

Abstract EN

The PPAR-γ gene encodes for at least 7 unique transcripts due to alternative splicing of five exons in the 5′-untranslated region (UTR).

The translated region is encoded by exons 1–6, which are identical in all isoforms.

This study investigated the role of the 5′-UTR in regulating the efficiency with which the message is translated to protein.

A coupled in vitro transcription-translation assay demonstrated that PPAR-γ1, -γ2, and -γ5 are efficiently translated, whereas PPAR-γ4 and -γ7 are poorly translated.

An in vivo reporter gene assay using each 5′-UTR upstream of the firefly luciferase gene showed that the 5′-UTRs for PPAR-γ1, -γ2, and -γ4 enhanced translation, whereas the 5′-UTRs for PPAR-γ5 and -γ7 inhibited translation.

Models of RNA secondary structure, obtained by the mfold software, were used to explain the mechanism of regulation by each 5′-UTR.

In general, it was found that the translational efficiency was inversely correlated with the stability of the mRNA secondary structure, the presence of base-pairing in the consensus Kozak sequence, the number of start codons in the 5′-UTR, and the length of the 5′-UTR.

A better understanding of posttranscriptional regulation of translation will allow modulation of protein levels without altering transcription.