What is the function of microRNAs in gene expression?

MicroRNAs (miRNAs) play a crucial role in the regulation of gene expression by specifically targeting mRNA molecules. The primary function of miRNAs is to bind to complementary sequences on their target mRNAs, leading to two key outcomes: mRNA degradation or translational repression. When miRNAs hybridize with their target mRNAs, they can either initiate degradation through the recruitment of the RNA-induced silencing complex (RISC) or hinder the translation of the mRNA without causing degradation.

This regulatory mechanism is vital for maintaining cellular homeostasis and controlling various biological processes, including development, differentiation, and responses to environmental changes. The precise modulation of gene expression by miRNAs allows for fine-tuning of protein production in response to specific cellular conditions, thus playing a critical role in gene regulatory networks.

In contrast, other functions implied in the options pertain to different RNA processing activities or mechanisms that are not primarily associated with the action of miRNAs. For example, promoting RNA stability refers to processes involved with polyadenylation or protective structures that fend off degradation, which is outside the scope of miRNA function. Enhancing translation is generally linked to factors that assist ribosome binding or activity on an mRNA, opposing the repressive role of miRNAs