The intergenic spacer of the Drosophila Adh-Adhr dicistronic mRNA stimulates internal translation initiation

Area of Science:

• Molecular Biology
• Genetics
• Gene Expression

Background:

• Eukaryotic ribosomes typically initiate translation at the 5' end of messenger RNAs (mRNAs), limiting the translation of polycistronic mRNAs.
• Internal ribosome entry site (IRES) elements have been proposed to mediate cap-independent translation initiation at internal open reading frames (ORFs).
• Dicistronic mRNAs, containing two ORFs, have been observed in some eukaryotes, suggesting mechanisms for internal translation initiation.

Purpose of the Study:

• To investigate the translation mechanism of the dicistronic Adh-Adhr mRNA in Drosophila melanogaster.
• To determine the role of the intergenic spacer in enhancing the translation of internal ORFs.
• To explore the potential link between pre-mRNA splicing and internal translation initiation.

Main Methods:

• Construction of dicistronic reporter genes in Drosophila.
• Analysis of reporter gene expression in S2 cells and adult flies.
• Comparison of translation yields from constructs with and without introns.

Main Results:

• The full-length intergenic spacer significantly enhanced the translation of the internal ORF in dicistronic reporters.
• Higher translation yields were observed for transcripts derived from intron-containing constructs.
• These findings suggest that the intergenic spacer facilitates internal translation initiation.

Conclusions:

• The intergenic spacer of the Adh-Adhr mRNA acts as an enhancer for internal ORF translation in Drosophila.
• Pre-mRNA splicing appears to play a role in promoting efficient internal translation initiation.
• This study provides insights into mechanisms regulating translation of polycistronic mRNAs in eukaryotes.