科学家在活体细胞中观测DNA活动

April 21, 2011 − (BRONX, NY) − Researchers at Albert Einstein College of Medicine of Yeshiva University have for the first time observed the activity of a single gene¹ in living cells. In an unprecedented² study, published in the April 22 online edition of Science, Einstein scientists were able to follow, in real time, the process of gene transcription, which occurs when a gene converts its DNA³ information into molecules⁵ of messenger RNA (mRNA) that go on to make the protein coded by the gene. Robert Singer, Ph.D., co-director of the Gruss Lipper Biophotonics Center at Einstein and professor and co-chair of anatomy⁶（解剖） and structural⁷ biology, is senior author of the paper. The study's lead author is Daniel Larson, Ph.D., previously⁸ a member of Dr. Singer's lab and now an investigator⁹ at the National Cancer Institute and head of the institute's Systems Biology of Gene Expression Section.

Using florescent（开花的） proteins, the researchers were able to follow mRNA activity by inserting DNA sequences into a gene in live yeast¹⁰ cells. RNA made from these sequences bound a modified green fluorescent¹¹ protein; expression of the entire gene resulted in mRNA molecules that were visible with fluorescent light. Gene transcription is a key step in synthesizing proteins, which govern the body's structure and function and underlie¹² many diseases when present in mutated form or in aberrant¹³（异常的） amounts.

The study involved monitoring the activity of RNA polymerase—the enzyme¹⁴ that constructs mRNA molecules by linking single nucleotides（核苷酸） together into a molecular¹⁵ chain. The researchers were able to directly observe and measure the key steps involved in transcription: initiation¹⁶ (triggered when proteins called transcription factors bind¹⁷ to the promoter region of the gene), elongation (the progressive lengthening¹⁸ of mRNA as RNA polymerase adds more nucleotides to it) and termination (when mRNA breaks free from its DNA template, eventually migrating from the cell nucleus¹⁹ to the cytoplasm细胞质 to serve as a blueprint²⁰ for protein construction).

"The view of transcription in yeast that emerges from this study is that its initiation seems to be a random²¹ event that depends on the success of transcription factors searching through the yeast nucleus looking for a particular gene's promoter region," said Dr. Singer. "By contrast, once initiation occurs, RNA polymerase recruits individual nucleotides for the growing mRNA molecule⁴ in an efficient and predictable manner."

"Understanding how gene expression is regulated in a single-celled organism such as yeast is a first step in understanding the same processes in humans, which have a vastly larger and more complex genome," said Dr. Larson. "But fundamentally, the same molecular laws governing transcription factors will still apply."