MiRNA biogenesis pathway

miRNA Biogenesis Pathway: Key Steps

1. Transcriptional Level:

pri-miRNA Transcription:

RNA Polymerase II transcribes the miRNA gene into a primary miRNA (pri-miRNA) transcript.

pri-miRNA is a long, single-stranded RNA with a hairpin structure.

2. Post-Transcriptional Level:

Drosha Processing:

In the nucleus, Drosha (an RNase III enzyme) and its cofactor DGCR8 cleave the pri-miRNA into a shorter, precursor miRNA (pre-miRNA).

Nuclear Export:

The pre-miRNA is exported from the nucleus to the cytoplasm by Exportin-5.

Dicer Processing:

In the cytoplasm, Dicer (another RNase III enzyme) cleaves the pre-miRNA to generate a double-stranded mature miRNA (~22 nucleotides long).

RISC Loading:

One strand (guide strand) of the mature miRNA is incorporated into the RNA-Induced Silencing Complex (RISC).

Target mRNA Regulation:

RISC-bound miRNA binds to complementary sequences in the target mRNA, leading to mRNA degradation or translational repression, depending on the degree of complementarity.