HTF: A b-ZIP transcription factor that is closely related to the human XBP/TREB5 and is activated by hepatocellular carcinoma in rats.
We screened for rat hepatocellular carcinoma (HCC)-related genes by a novel cDNA subtraction method and obtained one gene. This gene was transcribed as 2.0- and 2.5-kb mRNAs, and its transcription was specifically enhanced in HCC. These cDNAs had the same open reading frame, but the 2.5 kb transcript had an extra 495 bases of 5'-UTR at the 5'-terminus. The deduced aa sequence revealed a basic-leucine zipper (b-ZIP) and proline/glutamine-rich structures, both of which are characteristic motifs for transcription factors. We designated the translation product of this gene HTF (Hepatocarcinogenesis-related Transcription Factor). Electrophoretic mobility shift assay demonstrated the DNA-binding ability of the recombinant HTF. It is most interesting that HTF had a considerable homology with human XBP/TREB5, which has been reported to be a binding factor for the X-box of the MHC class II gene and for the 21-bp enhancer of the HTLV-1 LTR. Genomic Southern analysis suggested that the 2.0- and 2.5-kb mRNAs are transcribed by a dual promoter of a single gene. Our results may suggest that HTF is a b-ZIP-type transcription factor involved in rat hepatocellular carcinoma.
Kishimoto
T
T
Department of Biology, Faculty of Science, Chiba University, Japan.
Kokura
K
K
Kumagai
Y
Y
Wakamatsu
T
T
Makino
Y
Y
Tamura
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry*; D005973:Glutamine; D006801:Humans; D016350:Leucine Zippers; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms / Q000378:metabolism*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D009687:Nuclear Proteins / Q000737:chemistry*; D009838:Oligodeoxyribonucleotides; D016366:Open Reading Frames; D011392:Proline; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry*; D014158:Transcription, Genetic; D000071717:X-Box Binding Protein 1
D050976:Basic-Leucine Zipper Transcription Factors; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605545:Xbp1 protein, rat; D005973:Glutamine; D011392:Proline