HOXC13 is involved in the regulation of human hair keratin gene expression.
At present, HOXC13 is the only member of the HOX multigene family that produces a fragile hair phenotype when mutated or overexpressed in mice. To determine whether hair keratin genes are targets for this transcription factor, we analyzed the HOXC13 responsiveness of human hair keratin genes, whose expression matched that of nuclear HOXC13, immunologically revealed in cells of the lower hair-forming compartment of the human anagen hair follicle. We show that HOXC13, but not a homeobox-deleted HOXC13, strongly activated the promoters of the genes, with the respective proximal promoter regions being sufficient for optimal activation. The hair keratin promoters contained numerous putative Hox binding core motifs TAAT, TTAT, and TTAC. Electrophoretic mobility shift assays revealed that HOXC13 bound exclusively to distinct TAAT and TTAT core motifs that were clearly concentrated in the proximal promoter regions. A comparison of the sequences flanking HOXC13 binding and nonbinding core motifs, respectively, allowed the deduction of an extended 8-bp HOXC13 consensus binding sequence TT(A/T)ATNPuPu. Thus, the DNA binding conditions for HOXC13 were distinct from those of other members of the paralogous group 13, i.e. murine Hoxb13 and HOXd13, for which previous investigations yielded the consensus binding sequence TTTA(T/C)NPuPu. Collectively, our data speak for a direct involvement of HOXC13 in the control of hair keratin expression during early trichocyte differentiation.
Jave-Suarez
Luis Felipe
LF
Divisions of Tumor Cell Regulation and Cell Biology, German Cancer Research Center, 69120 Heidelberg, Germany.
Winter
Hermelita
H
Langbein
Lutz
L
Rogers
Michael A
MA
Schweizer
Jürgen
J
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D017931:DNA Primers; D004173:Dipodomys; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D018859:Hair Follicle / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007633:Keratins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D016385:TATA Box; D014158:Transcription, Genetic; D014162:Transfection
D017931:DNA Primers; D018398:Homeodomain Proteins; C485834:Hoxc13 protein, mouse; D012333:RNA, Messenger; D007633:Keratins