Now, research at Cornell University, using the fruit fly as a model system, has confirmed a theory about one step in the process by showing that a protein complex known as FACT is positioned in living cells at sites where chromosomal DNA is unpacked so that its code can be read. It is part of what the researchers call "a sophisticated molecular machine" that is not yet completely understood. The research is reported in the latest edition (Aug. 22) of the journal Science .
"This process is fundamental to the expression of all genes, whether they are normally expressed genes or genes that contribute to disease -- all these use the same machinery," says John T. Lis, Cornell professor of molecular biology and genetics, who supervised the research.
Two other related papers on the topic also will be published in the same issue of Science from groups at the Robert Wood Johnson Medical School and Harvard Medical School. The cover image of the issue, from the Cornell and Robert Wood Johnson research groups, shows FACT appearing at the same locations as two other transcription factors on fruit fly (Drosophila ) chromosomes.
To fit into the nucleus of a cell, DNA must be packed into folded structures called nucleosomes that in turn form higher order structures. When the cell needs to manufacture a particular protein, nucleosomes open to expose the part of the chromosomal DNA where the gene for that protein is located. This allows an enzyme called RNA polymerase II to contact the gene to transcribe its code onto another molecule called messenger RNA. In turn, the messenger RNA travels out of the nucleus into the cytoplasm and to another cell structure called a ribosome, where a protein is manufactured according to the transcribed code.
Contact: Bill Steele
Cornell University News Service