Selective microRNA uridylation by Zcchc6 (TUT7) and Zcchc11 (TUT4)

Area of Science:

• Molecular Biology
• Developmental Biology
• RNA Biology

Background:

• MicroRNAs (miRNAs) are key regulators of gene expression.
• Post-transcriptional modifications, including 3' end nucleotide additions, affect miRNA function.
• The enzymes responsible for specific miRNA 3' end modifications are largely unknown.

Purpose of the Study:

• To identify the enzymes responsible for 3' end mono-uridylation of specific microRNAs.
• To elucidate the mechanism and regulatory role of miRNA uridylation.
• To investigate the impact of miRNA uridylation on gene regulation and development.

Main Methods:

• Small RNA sequencing to identify modified miRNAs.
• In vitro biochemical assays using purified terminal uridyl transferases (TUTases).
• Cellular depletion of TUTases (Zcchc6/TUT7 and Zcchc11/TUT4) and subsequent miRNA analysis.
• Zebrafish embryo experiments with TUTase inhibition.

Main Results:

• Zcchc6 (TUT7) and Zcchc11 (TUT4) were identified as the primary enzymes catalyzing 3' mono-uridylation of specific miRNAs involved in cell differentiation and Homeobox (Hox) gene control.
• A bipartite sequence motif was biochemically defined as necessary and sufficient for Zcchc6/11-mediated uridylation.
• Depletion of Zcchc6/11 in cells led to a selective loss of miRNA uridylation and a compensatory increase in miRNA adenylation.
• Inhibition of TUTases in zebrafish embryos resulted in developmental defects and aberrant Hox gene expression.

Conclusions:

• Zcchc6 and Zcchc11 are key regulators of miRNA 3' end uridylation, controlling the stability and function of specific miRNA subsets.
• This study reveals the molecular basis for selective miRNA uridylation and its role in precise control of miRNA modifications.
• MiRNA uridylation by Zcchc6/11 has significant implications for gene regulatory networks, particularly in the context of development and Homeobox gene regulation.