Identification of EloA-BP1, a novel Elongin A binding protein with an exonuclease homology domain.
The Elongin complex stimulates the rate of transcription elongation by RNA polymerase II by suppressing the transient pausing of the polymerase at many sites along the DNA template. Elongin is composed of a transcriptionally active A subunit, and two positive regulatory B and C subunits. Although the NH(2)-terminal approximately 120 amino acid region of Elongin A is dispensable for its transcriptional activity in vitro, it shares significant sequence similarity with the NH(2)-terminus of other class of transcription factors SII and CRSP70, suggesting that the NH(2)-terminus mediates interactions important for the regulation of transcription in vivo. To identify proteins that can bind to these conserved sequences, a human B cell cDNA library was screened using the NH(2)-terminus of Elongin A as bait in a yeast two-hybrid system. Here, we report on the cloning and characterization of a novel human exonuclease domain-containing protein, Elongin A-binding protein 1 (EloA-BP1). EloA-BP1 is composed of 1221 amino acids and its mRNA is ubiquitously expressed. Double immunofluorescence labeling in COS7 cells suggested that EloA-BP1 and Elongin A are colocalized to the cell nucleus. By using an in vitro binding assay, we show that EloA-BP1 is capable of binding not only the NH(2)-terminal approximately 120 amino acid region of Elongin A, but also that of SII. Although the purified EloA-BP1 had no detectable effect on the rate of transcription elongation in vitro, it may play some role in the regulation of elongation in vivo.
Tamura
Kenji
K
Department of Functional Genomics, Faculty of Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku, Kochi, Japan.
Miyata
Keikichi
K
Sugahara
Kazunori
K
Onishi
Saburo
S
Shuin
Taro
T
Aso
Teijiro
T
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D000075065:Elongin; D005092:Exonucleases / Q000737:chemistry*; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007313:Insecta; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012319:RNA Polymerase II / Q000737:chemistry; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
D002352:Carrier Proteins; D018076:DNA, Complementary; C000616397:ELOA protein, human; C000616404:Eloa protein, rat; D000075065:Elongin; D009687:Nuclear Proteins; C477883:REXO1 protein, human; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D012313:RNA; D004247:DNA; D005982:Glutathione Transferase; D012319:RNA Polymerase II; D005092:Exonucleases