Parsing a process of life
Transcription is the first step in gene expression, the process by which information contained in a gene is used to make functional products, such as proteins. It’s fundamental to life and, not surprisingly, extraordinarily complicated.
In the July 22, 2012 issue of Nature Structural & Molecular Biology, Dong Wang, PhD, assistant professor in the Skaggs School of Pharmacy and Pharmaceutical Science, and colleagues further elucidate how transcription is altered by some forms of cytosine.
Cytosine, of course, is one of the four main bases that comprise DNA and RNA (along with adenine, guanine and thymine; uracil replacing thymine in RNA). There are at least five forms of cytosine in human DNA. Wang and colleagues have discovered that two recently identified forms of cytosine, known as 5fC and 5caC, significantly reduce the transcription rate in vitro.
The finding, said Wang, suggests that some forms of cytosine (and perhaps other players yet-to-be-identified) may provide another layer of regulation and fine-tuning to the transcription process. By slowing the activity of RNA polymerase II, a major transcriptional enzyme, 5fC and 5caC may make it easier for other enzymes, proteins and factors to play their parts in the larger act of gene expression.
Photo: Structure of RNA Polymerase II, a key enzyme in mammalian cells that catalyzes the transcription of DNA into messenger RNA, the molecule that in turn dictates the order of amino acids in proteins. Courtesy of National Institute of General Medical Sciences.