miR-148 targets human DNMT3b protein coding region.

Area of Science:

• Molecular Biology
• Genetics
• RNA Biology

Background:

• MicroRNAs (miRNAs) are key regulators of gene expression, typically binding to the 3' untranslated regions (3'UTRs) of mRNAs in animals.
• Plant miRNAs, however, often interact with coding regions of mRNAs.
• The precise mechanisms and targets of miRNA regulation in human gene expression are still being elucidated.

Purpose of the Study:

• To investigate the regulatory role of human miR-148 on the DNA methyltransferase 3b (Dnmt3b) gene.
• To determine if miRNAs can target coding sequences of human genes.
• To explore the impact of such targeting on the expression of different Dnmt3b splice variants.

Main Methods:

• Investigated miR-148's interaction with Dnmt3b using computational analysis and experimental validation.
• Utilized overexpression and knockdown (short-hairpin RNA) of miR-148 in human cells.
• Performed site-directed mutagenesis to confirm the target site in the Dnmt3b coding sequence.
• Analyzed the expression levels of different Dnmt3b splice variants (Dnmt3b1, Dnmt3b2, Dnmt3b3, Dnmt3b4).

Main Results:

• Human miR-148 directly represses Dnmt3b gene expression by binding to a conserved site within its coding sequence.
• This regulatory mechanism affects specific Dnmt3b splice variants, notably Dnmt3b1, but not Dnmt3b3, which lacks the target site.
• Overexpression of miR-148 decreased DNMT3b1 expression, while its repression increased DNMT3b1 expression, confirming a direct regulatory link.

Conclusions:

• The coding sequence of Dnmt3b mediates regulation by the miR-148 family, challenging the traditional view of miRNA targeting in animals.
• Provides evidence for miRNA targeting of coding regions in human genes.
• Suggests that miRNA-mediated targeting of coding sequences may play a significant role in regulating the expression of gene splice variants.