Expression of miRNA-Targeted and Not-Targeted Reporter Genes Shows Mutual Influence and Intercellular Specificity

Area of Science:

• Molecular Biology
• Gene Regulation
• RNA Interference

Background:

• RNA-induced silencing complexes (RISCs) regulate translation via Argonaute proteins and micro-RNAs (miRNAs).
• Mechanisms of specific cellular responses to miRNAs and complex formation remain unclear.
• Understanding miRNA-target interactions is crucial for deciphering gene regulation.

Purpose of the Study:

• To investigate cellular responses to specific miRNAs and the formation of miRNA-protein complexes.
• To explore how miRNA targeting affects both targeted and non-targeted reporter gene expression.
• To determine if non-targeted transcripts can be reliably used for normalization in miRNA studies.

Main Methods:

• Utilized Renilla and firefly luciferase reporter genes in psiCHECK-2 plasmids transfected into human HCT116 or Me45 cells.
• Introduced specific miRNAs (miRNA-21-5p, miRNA-24-3p, Let-7 family) targeting the Renilla gene's 3'UTR.
• Analyzed mRNA-protein complexes using sucrose gradient centrifugation and anti-miRNA oligoribonucleotides.

Main Results:

• miRNA targeting exhibited specificity, with miRNA-21-5p inhibiting Renilla translation, while others had minimal or positive effects.
• mRNA-protein complexes varied based on miRNA and cell type.
• Non-targeted firefly luciferase expression was unexpectedly affected by miRNA targeting of Renilla transcripts.
• Both targeted and non-targeted transcripts co-fractionated in sucrose gradients and responded to anti-miRNA treatments.

Conclusions:

• miRNAs can modulate the expression of non-targeted transcripts alongside targeted ones.
• Using non-targeted transcripts for normalization in miRNA experiments may introduce bias.
• Hypothetical mechanisms for miRNA-mediated regulation of non-targeted transcripts warrant further investigation.