Translational control elements in the major human transforming growth factor-beta 1 mRNA

Area of Science:

• Molecular Biology
• Gene Expression Regulation
• Cellular Biology

Background:

• Transforming growth factor-beta 1 (TGF-beta 1) is a crucial cytokine.
• Differential translation efficiency of TGF-beta isoforms is not well understood.
• The 2.4 kb TGF-beta 1 transcript is known to be poorly translated.

Purpose of the Study:

• To investigate the mechanisms underlying the poor translation of TGF-beta 1 mRNA.
• To determine the role of 5' and 3' untranslated regions (UTRs) in TGF-beta 1 translational regulation.
• To compare the translation efficiency of TGF-beta 1 and TGF-beta 2 transcripts.

Main Methods:

• Polysome analysis in cultured cells and mouse liver.
• Deletion analysis of TGF-beta 1 5' and 3' UTRs.
• In vitro and in vivo translation assays using synthetic TGF-beta 1 mRNAs in MCF-7 cells.

Main Results:

• The major 2.4 kb TGF-beta 1 transcript exhibits poor translation in vivo and in cultured cells, unlike the efficiently translated TGF-beta 2 transcripts.
• Both 5' and 3' UTRs of TGF-beta 1 stimulated translation in vitro, despite high G+C content.
• In vivo, limited trans-acting factors interact with the 5'UTR, conferring translational inhibition, with multiple stimulatory and inhibitory regions identified within the 5'UTR.

Conclusions:

• Poor translation of TGF-beta 1 mRNA is attributed to suboptimal initiation context and inhibitory interactions involving limited trans-acting factors and cis-elements within the 5'UTR.
• These findings have implications for understanding the translation of shorter TGF-beta 1 variants.
• The study provides a basis for further high-resolution mapping of regulatory elements in TGF-beta 1 mRNA.