Termination of transcription in nucleoli isolated from Tetrahymena.

AUTOR(ES)

Leer, J C

RESUMO

Correct termination of transcription of the rRNA gene in nucleoli isolated from Tetrahymena is dependent on a protein factor with a molecular weight between 50,000 and 100,000. At low ionic strength the endogenous RNA polymerase synthesizes a transcript identical in size to the precursor rRNA extracted from cells. In the presence of ammonium sulfate, however, the RNA polymerase reads through the normal termination point as demonstrated by size and hybridization studies of the transcript. After ammonium sulfate treatment, rDNA associated with chromosomal proteins (r-chromatin) can be separated from the termination factor by differential centrifugation. The endogenous RNA polymerase on the salt-treated r-chromatin is no longer able to recognize the normal terminator even at low ionic strength. Normal termination properties can be reconstituted by complementation with intact nucleoli or with a protein factor extracted from nucleoli.

Documentos Relacionados

• Transcriptional properties of nucleoli isolated from Tetrahymena.
• In vitro splicing of the ribosomal RNA precursor in isolated nucleoli from Tetrahymena.
• Presence of calmodulin in Tetrahymena.
• The complete amino acid sequence of an HMG-like protein isolated from the macronucleus of Tetrahymena.
• Properties of in vitro transcription by isolated Xenopus oocyte nucleoli.