Nogales is a leading authority on electron microscopy and holds joint appointments with Berkeley Lab, the University of California (UC) at Berkeley, and the Howard Hughes Medical Institute (HHMI). She is the corresponding author of a paper describing this research in the journal Cell, titled "Human TFIID Binds to Core Promoter DNA in a Reorganized Structural State." Co-authors are Michael Cianfrocco, George Kassavetis, Patricia Grob, Jie Fang, Tamar Juven-Gershon and James Kadonaga.
The growing number of organisms whose genomes have been sequenced and made available for comparative analyses shows that the total number of genes in an organism's genome is no measure of its complexity. The fruit fly, Drosophila, for example, is far more complex than the nematode worm, Caenorhabditis elegans, but has about 6,000 fewer genes than the worm's 20,000. The total number of human genes is estimated to fall somewhere between 30,000 and 40,000. By comparison, the expression of the genes of both the fruit fly and the nematode are regulated through about 1,000 transcription factors, whereas the human genome boasts approximately 3,000 transcription factors. That multiple transcription factors often act in various combinations with one another creates even more evolutionary roads to organism complexity.
"Although the number of protein coding genes has remained fairly constant throughout metazoan evolution, the number of regulatory DNA elements has increased dramatically," Nogales says. "Our discovery of the existence of two structurally and functionally distinct forms of TFIID suggests a potential molecular mechanism by which a combination of transcription factors can tune the expression level of genes and thereby give rise to a diversity of outcomes."
Despite its critical role in transcription, high-resolution structural information of TFIID has been restricted to
to crystal structures of a handfu
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory