Acanthamoeba castellanii contains a ribosomal RNA enhancer binding protein which stimulates TIF-IB binding and transcription under stringent conditions.
The intergenic spacer (IGS) of Acanthamoeba castellanii rRNA genes contains repeated elements which are weak enhancers for transcription by RNA polymerase I. A protein, EBF, was identified and partially purified which binds to the enhancers and to several other sequences within the IGS, but not to other DNA fragments, including the rRNA core promoter. No consensus binding sequence could be discerned in these fragments and bound factor is in rapid equilibrium with unbound. EBF has functional characteristics similar to vertebrate upstream binding factors (UBF). Not only does it bind to the enhancer and other IGS elements, but it also stimulates binding of TIF-IB, the fundamental transcription initiation factor, to the core promoter and stimulates transcription from the promoter. Attempts to identify polypeptides with epitopes similar to rat or Xenopus laevis UBF suggest that structurally the protein from A.castellanii is not closely related to vertebrate UBF.
Yang
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Q
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA.
Radebaugh
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CA
Kubaska
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W
Geiss
G K
GK
Paule
M R
MR
D000048:Acanthamoeba / Q000235:genetics*; D000818:Animals; D001665:Binding Sites; D003429:Cross Reactions; D018983:DNA Footprinting; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins; D011485:Protein Binding; D015800:Protozoan Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000096:biosynthesis; D012091:Repetitive Sequences, Nucleic Acid; D014157:Transcription Factors / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D006657:Histones; D035463:Pol1 Transcription Initiation Complex Proteins; D015800:Protozoan Proteins; D012335:RNA, Ribosomal; D014157:Transcription Factors; C063844:transcription factor UBF; C063660:transcription initiation factor TIF-IB