miRNAs

MicroRNAs (miRNAs) are short, non-coding RNA molecules, typically about 20-24 nucleotides in length, that play a crucial role in the regulation of gene expression in eukaryotic organisms. They are highly conserved across species, indicating their fundamental biological importance. miRNAs function primarily by binding to complementary sequences in messenger RNA (mRNA) molecules, leading to mRNA degradation or the inhibition of translation, thereby reducing the production of specific proteins.

The biogenesis of miRNAs involves several processing steps. It begins with the transcription of primary miRNA (pri-miRNA) transcripts by RNA polymerase II, which are then processed in the nucleus by the enzyme Drosha into precursor miRNA (pre-miRNA). These pre-miRNAs are exported into the cytoplasm and further cleaved by the enzyme Dicer into mature miRNA duplexes. One strand of the duplex is incorporated into the RNA-induced silencing complex (RISC), which guides the complex to target mRNAs based on sequence complementarity.

miRNAs are involved in a wide array of biological processes, including development, differentiation, proliferation, apoptosis, and immune responses. Dysregulation of miRNA expression has been linked to various diseases, such as cancer, cardiovascular diseases, and neurological disorders, making them of interest both as potential biomarkers and therapeutic targets.

Research into miRNAs continues to expand, revealing their versatility and significance in cellular function. Their ability to fine-tune gene expression underscores their role as key regulators in maintaining cellular homeostasis and organismal health.