How does RNA splicing contribute to gene expression?

RNA splicing contributes to gene expression by removing introns and joining exons, creating a mature mRNA molecule for protein synthesis.

RNA splicing is a crucial process in the expression of most eukaryotic genes. It involves the removal of non-coding sequences, known as introns, from the pre-mRNA molecule, and the joining together of the remaining coding sequences, known as exons. This process results in a mature mRNA molecule that can be translated into a protein by the ribosome.

The process of RNA splicing begins in the nucleus, where the pre-mRNA molecule is transcribed from the DNA template. The introns and exons are initially both included in this molecule. The splicing machinery, known as the spliceosome, then recognises specific sequences at the intron-exon boundaries. The spliceosome is composed of several small nuclear ribonucleoproteins (snRNPs), which bind to these sequences and catalyse the splicing reaction.

The introns are removed in a two-step process. First, the 5' end of the intron is cut and folded back on itself to form a loop. This is followed by the cutting of the 3' end of the intron, releasing the loop and joining the two exons together. The excised intron is then degraded, while the mature mRNA molecule is exported from the nucleus to the cytoplasm for translation.

RNA splicing is not only essential for the removal of introns, but it also contributes to the diversity of proteins that can be produced from a single gene. This is due to a process known as alternative splicing, where different combinations of exons are joined together to produce different mRNA molecules. This means that a single gene can give rise to multiple proteins, depending on which exons are included in the mRNA. This greatly increases the complexity and versatility of the proteome, allowing cells to respond to different conditions and perform different functions.

In summary, RNA splicing is a vital process in gene expression, ensuring that the correct coding sequences are included in the mRNA for protein synthesis. It also contributes to protein diversity through alternative splicing, enhancing the functional capabilities of the cell.