xUBF contains a novel dimerization domain essential for RNA polymerase I transcription.
Xenopus laevis upstream binding factor (xUBF) is an RNA polymerase I transcription factor that is required for formation of the stable initiation complex. The 701-amino-acid protein contains three regions of homology to the chromosomal protein HMG1 (the HMG boxes), which act in comparative independence to cause DNA binding. DNA binding is augmented by a 102-residue amino-terminal domain that causes xUBF to form dimers. The dimerization domain is bipartite in structure, consisting of two regions with the potential to form amphipathic helices, separated by a gap of at least 22 amino acids. The carboxyl half of xUBF is relatively dispensable for transcription (including an 87-residue acidic tail). However, either altering the number of HMG boxes or interfering with dimerization eliminates transcription. The gap region of the dimerization domain is dispensable for dimerization but is absolutely required for transcription. This suggests that the gap region has a critical function in transcription distinct from any effect on dimerization or DNA binding.
Basic Sciences Division, Hutchinson Cancer Research Center, Seattle, Washington 98104.
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D004275:DNA, Ribosomal / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005976:Glutaral / Q000737:chemistry; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009698:Nucleoproteins / Q000737:chemistry; D009838:Oligodeoxyribonucleotides / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D035463:Pol1 Transcription Initiation Complex Proteins; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic / Q000502:physiology; D011487:Protein Conformation; D012318:RNA Polymerase I / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D014982:Xenopus laevis / Q000502:physiology
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009698:Nucleoproteins; D009838:Oligodeoxyribonucleotides; D035463:Pol1 Transcription Initiation Complex Proteins; D014157:Transcription Factors; C063844:transcription factor UBF; D012318:RNA Polymerase I; D005976:Glutaral