According to the textbook model of gene transcription, the process is sparked by the recruitment of RNA polymerase II (Pol II) to a gene’s promoter. But a 2007 Cell paper from Richard Young’s lab at the Whitehead Institute in Cambridge, Mass., suggests the picture may be significantly more complicated at many genes, particularly those encoding key regulators of development.
That study, a Hot Paper this month, took a genome-wide look at transcription initiation in human embryonic stem cells. The authors found evidence for transcription initiation—that is, Pol II was recruited and the right chromatin marks were present—in the majority of all protein-coding genes. This was a perplexing result, since no more than 50% of such genes were thought to be undergoing transcription.1 In other words, according to the paper, transcription is initiated in most protein-coding genes, but only a subset of those are actually transcribed. Some additional mechanism, then, must ...
