The RNA polymerase I transcription factor xUBF contains 5 tandemly repeated HMG homology boxes.
The RNA polymerase I transcription factor UBF has been identified in human, mouse, rat and Xenopus and the primary structure of the human protein has been determined. Human UBF was shown to contain four tandem homologies to the folding domains of the HMG1 and 2 proteins and hence to belong to a previously unrecognised family of 'HMG-box' transcription factors. Here, cDNA clones encoding the Xenopus laevis UBF (xUBF) have been isolated and sequenced. Northern and Southern blots revealed that in tissue culture cells, xUBF is coded on a single major mRNA size species by a small number of genes. The deduced primary structure of xUBF is highly homologous with the human protein except for a central deletion which removes most of one HMG-box. This explains the major size difference between the X. laevis and human proteins and may well explain their different transcriptional specificities. It is shown that xUBF contains 5 tandemly repeated HMG-boxes and that by analogy the human protein contains 6.
Bachvarov
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Centre de Recherche en Cancérologie de l'Université Laval, Québec, Canada.
Moss
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D004247:DNA; D006609:High Mobility Group Proteins / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D012318:RNA Polymerase I / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins; D014982:Xenopus laevis
D006609:High Mobility Group Proteins; D014157:Transcription Factors; C062332:UBFT protein, Xenopus; D029867:Xenopus Proteins; D004247:DNA; D012318:RNA Polymerase I