Pbx proteins display hexapeptide-dependent cooperative DNA binding with a subset of Hox proteins.
The human proto-oncogene PBX1 codes for a homolog of Drosophila extradenticle, a divergent homeo domain protein that modulates the developmental and DNA-binding specificity of select HOM proteins. We demonstrate that wild-type Pbx proteins and chimeric E2a-Pbx1 oncoproteins cooperatively bind a consensus DNA probe with HoxB4, B6, and B7 of the Antennapedia class of Hox/HOM proteins. Specificity of Hox-Pbx interactions was suggested by the inability of Pbx proteins to cooperatively bind the synthetic DNA target with HoxA10 or Drosophila even-skipped. Site-directed mutagenesis showed that the hexapeptide motif (IYPWMK) upstream of the Hox homeo domain was essential for HoxB6 and B7 to cooperatively bind DNA with Pbx proteins. Engraftment of the HoxB7 hexapeptide onto HoxA10 endowed it with robust cooperative properties, demonstrating a functional role for the highly conserved hexapeptide element as one of the molecular determinants delimiting Hox-Pbx cooperativity. The Pbx homeo domain was necessary but not sufficient for cooperativity, which required conserved amino acids carboxy-terminal of the homeo domain. These findings demonstrate that interactions between Hox and Pbx proteins modulate their DNA-binding properties, suggesting that Pbx and Hox proteins act in parallel as heterotypic complexes to regulate expression of specific subordinate genes.
Chang
C P
CP
Department of Pathology, Stanford University Medical Center, California 94305, USA.
Shen
W F
WF
Rozenfeld
S
S
Lawrence
H J
HJ
Largman
C
C
Cleary
M L
ML
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D017124:Conserved Sequence; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011233:Precipitin Tests; D011485:Protein Binding; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; C090460:HOXB4 protein, human; C093252:HOXB6 protein, human; C490538:HOXB7 protein, human; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; C490537:Hoxb6 protein, mouse; C000715470:MAS1 protein, human; D015514:Oncogene Proteins, Fusion; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C083400:PBX1 protein, human; C089847:E2A-Pbx1 fusion protein; C092119:Hoxa10 protein, mouse; D004247:DNA