Research reveals how cells process large genes

Important messages require accurate transmission. Big genes are especially challenging because they combine many coding segments (exons) that lie between long stretches of non-coding elements (introns). During processing, introns are snipped out and exons pasted together to form a template for proteins called messenger RNA (mRNA). Mistakes in RNA processing can reduce the expression of a functional protein or, worse, produce an abnormal protein that interferes with normal cell behavior. But just how a cell's molecular machinery eliminates long introns without making errors has puzzled scientists for years.