August 6, 2007 (BRONX, NY) Transcription the transfer of DNAs genetic information through the synthesis of complementary molecules of messenger RNA forms the basis of all cellular activities. Yet little is known about the dynamics of the process how efficient it is or how long it takes. Now, researchers at the Albert Einstein College of Medicine of Yeshiva University have measured the stages of transcription in real time. Their unexpected and surprising findings have fundamentally changed the way transcription is understood.
The researchers used pioneering microscopy techniques developed by Dr. Robert Singer, co-chair of anatomy & structural biology at Einstein and senior author of the study, which appears in the August issue of Nature Structural & Molecular Biology.
The study focused on RNA polymerase II--the enzyme responsible for transcription. During transcription, growing numbers of RNA polymerase II molecules assemble on DNA and then synthesize RNA by sequentially recruiting complementary RNA nucleotides.
To visualize the transcription process, the researchers used living mammalian cells, each of which contained 200 copies of an artificial gene that they had inserted into one of the cells chromosomes. Then, by attaching fluorescent tags to RNA polymerase II, they were able to closely monitor all three phases of the transcription process: binding of the enzyme molecules to DNA, initiation (when the enzyme links the first few RNA nucleotides together) and elongation (construction of the rest of the RNA molecule). As they observed the RNA polymerase II molecules attaching to DNA and making new RNA, they saw many cases where enzyme molecules attached and then promptly fell off.
One surprising finding was how inefficient the transcription process really is, particularly during its first two stages, says Dr. Singer. It turns out that only one percent of polymerases that bind to the gene actually remain on to help in
Contact: Karen Gardner
Albert Einstein College of Medicine