Transcription Factories
Active transcription units are clustered in the nucleus, in discrete sites called transcription factories or euchromatin. Such sites can be visualized by allowing engaged polymerases to extend their transcripts in tagged precursors (Br-UTP or Br-U) and immuno-labeling the tagged nascent RNA. Transcription factories can also be localized using fluorescence in situ hybridization or marked by antibodies directed against polymerases. There are ~10,000 factories in the nucleoplasm of a HeLa cell, among which are ~8,000 polymerase II factories and ~2,000 polymerase III factories. Each polymerase II factory contains ~8 polymerases. As most active transcription units are associated with only one polymerase, each factory usually contains ~8 different transcription units. These units might be associated through promoters and/or enhancers, with loops forming a ‘cloud’ around the factor.
Read more about this topic: Transcription (genetics)
Famous quotes containing the word factories:
“I know no more affecting lesson to our busy, plotting New England brains, than to go into one of our factories with which we have lined all the watercourses in the States. A man hardly knows how much he is a machine, until he begins to make telegraph, loom, press, and locomotive, in his own image.”
—Ralph Waldo Emerson (1803–1882)