microRNAs

MicroRNAs (miRNAs) are small, non-coding RNA molecules typically about 20-24 nucleotides in length that play a critical role in gene regulation. They are found in plants, animals, and many viruses, where they influence various biological processes by modulating gene expression at the post-transcriptional level.

MiRNAs are initially transcribed as primary transcripts called primary miRNAs (pri-miRNAs), which are processed in the nucleus by the Drosha enzyme into precursor miRNAs (pre-miRNAs). These precursors are then exported to the cytoplasm, where Dicer further cleaves them into mature miRNA duplexes. One strand of the duplex is incorporated into the RNA-induced silencing complex (RISC), guiding it to target messenger RNAs (mRNAs) through complementary base pairing.

The binding of miRNAs to target mRNAs typically results in either mRNA degradation or inhibition of translation, thereby decreasing the production of specific proteins. This regulatory mechanism underpins many cellular functions, including development, differentiation, apoptosis, and proliferation. Dysregulation of miRNAs has been implicated in various diseases, notably cancer, cardiovascular diseases, and neurological disorders.

Research on miRNAs has expanded dramatically since their discovery in the early 1990s, highlighting their importance as biomarkers for disease diagnosis and prognosis, as well as potential therapeutic targets. The study of miRNAs continues to provide insights into complex gene regulatory networks and the molecular basis of health and disease.

Overall, microRNAs are essential mediators of gene expression regulation, influencing a broad spectrum of biological functions by fine-tuning the levels of proteins within cells.