A Methyl Group Makes Us Complex

The biological complexity of humans doesn’t come from a preponderance of genes—we have about the same number of genes as the worm Caenorhabditis elegans. A team of scientists led by the National Cancer Institute’s Tom Misteli has figured out one way humans recruit the biomachinery that allows us to be more complicated with fewer genes (Science, DOI: 10.1126/science.1184208). Before mRNA from a single gene is translated into a protein, it gets spliced and diced into multiple forms, which are then translated into a variety of proteins, all giving rise to human complexity. Despite its importance, the splicing process is poorly understood, although scientists do know it involves elaborate biomachinery found in the cell nucleus that is composed of hundreds of proteins and catalytic RNAs. Misteli and coworkers determined that methylation of histone proteins, around which DNA winds, can recruit the splicing machinery. The researchers propose that as DNA is being transcribed into mRNA, the chemical decorations of nearby histone proteins determine how the RNA is chopped, and therefore how biological complexity is attained.