Identification of Two Forms of the RNA Polymerase I Transcription Factor UBF

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 8; pp. 3180 - 3184
• Main Authors: O'Mahony, Daniel J., Rothblum, Lawrence I.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15-04-1991; National Acad Sciences
• Subjects: Amino Acid Sequence; Amino acids; Animals; Base Sequence; Biological and medical sciences; Cell lines; Cloning, Molecular; Complementary DNA; DNA; DNA - genetics; DNA-Binding Proteins - genetics; Fundamental and applied biological sciences. Psychology; genes; HeLa cells; Humans; Messenger RNA; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Plasmids; Pol1 Transcription Initiation Complex Proteins; Polymerase Chain Reaction; Rats; Regulatory Sequences, Nucleic Acid; RNA; RNA Polymerase I - metabolism; RNA, Messenger - genetics; transcription factors; Transcription Factors - genetics; Transcription. Transcription factor. Splicing. Rna processing; UBF protein; Human; Vertebrata; Molecular form; Mammalia; Cell line; RNA polymerase 1; Nucleotide sequence; Rodentia; Transcription factor; Aminoacid sequence
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.8.3180

The structure of the rat homologue of the RNA polymerase I transcription factor UBF was investigated. The sequence of the protein was deduced from the sequence of overlapping cDNAs isolated from a cDNA library and from clones of the products generated by the polymerase chain reaction from random-primed, first-strand cDNA. The sequences of these clones indicated that there were two mRNAs for UBF and that the encoded proteins were similar but not identical. One form of rat UBF was essentially identical to human UBF. The second class of UBF mRNA contained an in-frame "deletion" in the coding region that results in the deletion of 37 amino acids from the predicted protein sequence. This deletion reduces the predicted molecular size of the encoded form of UBF by ≈4400 from 89.4 kDa to 85 kDa and significantly alters the structure of one of the four HMG-1 homology regions (HMG box-2) in that form of UBF. Evidence for the existence of two mRNAs in rat cells was confirmed by a probe protection assay, and we provide evidence that other vertebrate cells contain these same two forms of UBF mRNA. These results are consistent with the observation that UBF purified from four different vertebrates migrates as two bands upon SDS/PAGE. It has been hypothesized that the HMG motifs are the DNA-binding domains of UBF. Altering one of these "boxes," as in the second form of UBF, may alter the functional characteristics of the transcription factor. Thus, the existence of different forms of UBF may have important ramifications for transcription by RNA polymerase I.