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University of Pittsburgh study sheds light on how the cell decides precisely where to start copying a gene
Posté par Baltimore citywire
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The first stage of protein production is called transcription, in which a portion of the DNA strand is selected to be unraveled and copied. To initiate transcription, molecular machinery assembles at a defined region of the genome and melts the double stranded DNA, leaving a region of unwound DNA known as a “transcription bubble.” The machinery must then travel down the unwound strand, scanning for a place to begin, and initiate the process of transcription.
To better understand how a transcription start site is selected, researchers led by Craig D. Kaplan at the University of Pittsburgh carried out detailed studies on a common species of yeast, Saccharomyces cerevisiae, used since ancient times in brewing, winemaking and baking.
Their results, published October 2021 in the journal eLife Sciences, provide new insights into how far a certain protein SSl2 key roles scans in the promoter region, and how often it initiates transcription. The lead author is Tingting Zhao, currently at the Genomics and Bioinformatics Hub, Brigham and Women’s Hospital, Harvard Medical School in Boston.
Transcription factor TFIIH
In eukaryotic organisms (those with a distinct cell nucleus), transcription is carried out by a protein known as RNA polymerase POL II.
For the transcription to start, POL II requires help from at least five specialized proteins called general transcription factors. One of these transcription factors, known as TFIH, already was thought to play a crucial role in finding the start site for transcription.
However, the exact mechanism of transcription starter site selection (TSS) was not well understood. Kaplan’s team has made progress in this area by studying a protein called Ssl2.
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