The amino-terminal domain of the transcription termination factor TTF-I causes protein oligomerization and inhibition of DNA binding.
The transcription termination factor TTF-I binds specifically to an 18 bp DNA element in the murine ribosomal gene spacer and mediates termination of RNA polymerase I transcription. In this study, we have compared DNA binding and termination activity of recombinant full-length TTF-I (TTF-Ip130) with two deletion mutants lacking 184 and 322 N-terminal amino acids, respectively. All three proteins exhibit similar termination activity, but the DNA binding of TTF-Ip130 is at least one order of magnitude lower than that of the deletion mutants, indicating that the N-terminus represses the interaction of TTF-I with DNA. The inhibitory effect of the N-terminus can be transferred to a heterologous DNA binding domain and is separable from other activities of TTF-I. We show by several methods that TTF-Ip130, the N-terminal domain alone, and fusions of the N-terminus with the DNA binding domain of Oct2.2 form stable oligomers in solution. Thus, in contrast to previous studies suggesting that activation of TTF-I occurs through proteolysis, we demonstrate that full-length TTF-I mediates termination of rDNA transcription in vivo and in vitro and that the oligomerization state of TTF-I may influence its DNA binding activity.
Sander
E E
EE
Division of Molecular Biology of the Cell II, German Cancer Research Center, Heidelberg, Germany.
Mason
S W
SW
Munz
C
C
Grummt
I
I
D000818:Animals; D001704:Biopolymers; D002460:Cell Line; D004247:DNA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D018411:Spodoptera; D014157:Transcription Factors
D001704:Biopolymers; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D004247:DNA