The cysteine-rich LIM domains inhibit DNA binding by the associated homeodomain in Isl-1.
Recently, a new class of homeobox genes has been identified, called LIM-homeobox genes. These genes encode proteins which have two tandemly repeated cysteine motifs, referred to as LIM domains, in addition to a homeodomain. In addition, proteins with only LIM domains have been described but the function of the LIM domain is unknown. We have analysed the function of LIM domains using Isl-1 as a representative LIM-homeodomain protein. Employing protein prepared in bacterial cells, we show that the presence of the LIM domain in Isl-1 inhibits binding of the homeodomain to its DNA target. This in vitro inhibition can be released either by denaturation/renaturation of the protein or by truncation of the LIM domains. A similar inhibition is observed in vivo using reporter constructs. In addition we show that LIM domains in a chimeric protein can inhibit binding of the Ubx homeodomain to its target. The ability of LIM domains to inhibit DNA binding by the homeodomain provides a possible basis for negative regulation of LIM-homeodomain proteins in vivo.
Sánchez-García
I
I
MRC Laboratory of Molecular Biology, Cambridge, UK.
Osada
H
H
Forster
A
A
Rabbitts
T H
TH
D001483:Base Sequence; D001665:Binding Sites; D003545:Cysteine / Q000235:genetics* / Q000378:metabolism; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D019286:Endopeptidase K; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D017930:Genes, Reporter; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D008969:Molecular Sequence Data; D005810:Multigene Family; D009419:Nerve Tissue Proteins; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012697:Serine Endopeptidases / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; C063843:insulin gene enhancer binding protein Isl-1; D012697:Serine Endopeptidases; D019286:Endopeptidase K; D003545:Cysteine