The HMG-I(Y) A.T-hook peptide motif confers DNA-binding specificity to a structured chimeric protein.
Chromosomal translocations involving genes coding for members of the HMG-I(Y) family of "high mobility group" non-histone chromatin proteins (HMG-I, HMG-Y, and HMG-IC) have been observed in numerous types of human tumors. Many of these gene rearrangements result in the creation of chimeric proteins in which the DNA-binding domains of the HMG-I(Y) proteins, the so-called A.T-hook motifs, have been fused to heterologous peptide sequences. Although little is known about either the structure or biophysical properties of these naturally occurring fusion proteins, the suggestion has been made that such chimeras have probably assumed an altered in vivo DNA-binding specificity due to the presence of the A.T-hook motifs. To investigate this possibility, we performed in vitro "domain-swap" experiments using a model protein fusion system in which a single A. T-hook peptide was exchanged for a corresponding length peptide in the well characterized "B-box" DNA-binding domain of the HMG-1 non-histone chromatin protein. Here we report that chimeric A. T-hook/B-box hybrids exhibit in vitro DNA-binding characteristics resembling those of wild type HMG-I(Y) protein, rather than the HMG-1 protein. These results strongly suggest that the chimeric fusion proteins produced in human tumors as a result of HMG-I(Y) gene chromosomal translocations also retain A.T-hook-imparted DNA-binding properties in vivo.
Banks
G C
GC
Department of Biochemistry/Biophysics, Washington State University, Pullman, Washington 99164-4660, USA.
Mohr
B
B
Reeves
R
R
D000595:Amino Acid Sequence; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D025741:HMGA1a Protein; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D025741:HMGA1a Protein; D004247:DNA