Identification of a transcript release activity acting on ternary transcription complexes containing murine RNA polymerase I.
Termination of mammalian ribosomal gene transcription by RNA polymerase I (Pol I) requires binding of the nucleolar factor TTF-I (transcription termination factor for Pol I) to specific rDNA terminator elements. We have used recombinant murine TTF-I in an immobilized tailed template assay to analyze individual steps of the termination reaction. We demonstrate that, besides the TTF-I-DNA complex which stops elongating Pol I, an additional activity is required to release both the nascent transcript and Pol I from the template. Moreover, transcript release, but not TTF-I-directed pausing, depends on upstream sequences directly flanking the terminator element. Together, complete termination of Pol I transcription requires TTF-I bound to the terminator DNA, a stretch of thymidine residues upstream of the TTF-I-mediated pause site and an activity which releases the RNA transcript and Pol I from the DNA template.
Mason
S W
SW
Division of Molecular Biology of the Cell II, German Cancer Research Center, Heidelberg.
Sander
E E
EE
Grummt
I
I
D000818:Animals; D001685:Biological Factors / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D051379:Mice; D012318:RNA Polymerase I / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013728:Terminator Regions, Genetic; D013936:Thymidine / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic
D001685:Biological Factors; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; C504004:Ttf1 protein, mouse; D012318:RNA Polymerase I; D013936:Thymidine