Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

HeLa cells were encapsulated in agarose microbeads, permeabilized and incubated with Br-UTP in a 'physiological' buffer; then sites of RNA synthesis were immunolabelled using an antibody that reacts with BrRNA. After extending nascent RNA chains by < 400 nucleotides in vitro, ~ 300-500 focal synthetic sites can be seen in each nucleus by fluorescence microscopy. Most foci also contain a component of the splicing apparatus detected by an anti-Sm antibody. α-amanitin, an inhibitor of RNA polymerase II, prevents incorporation into these foci; then, using a slightly higher salt concentration, ~ 25 nucleolar foci became clearly visible. Both nucleolar and extra-nucleolar foci remain after nucleolytic removal of ~ 90% chromatin. An underlying structure probably organizes groups of transcription units into 'factories' where transcripts are both synthesized and processed.

Type

Journal article

Journal

EMBO Journal

Publication Date

01/01/1993

Volume

12

Pages

1059 - 1065