Characterization of a 300 kbp Region of Human DNA Containing the Type II Hair Keratin Gene Domain

• Published in: Journal of investigative dermatology Vol. 114; no. 3; pp. 464 - 472
• Main Authors: Rogers, Michael A., Winter, Hermelita, Wolf, Christian, Schweizer, Jürgen, Langbein, Lutz
• Format: Journal Article
• Language: English
• Published: Danvers, MA Elsevier Inc 01.03.2000; Nature Publishing; Elsevier Limited
• Subjects: Amino Acid Sequence; Base Sequence; Biological and medical sciences; chromosome 12q13; Dermatology; DNA - chemistry; gene expression; Gene Expression - physiology; hair follicle; Hair Follicle - chemistry; Humans; Investigative techniques, diagnostic techniques (general aspects); Keratins - genetics; Medical sciences; Molecular Sequence Data; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; promoter; Protein Structure, Tertiary; Pseudogenes - physiology; Sequence Homology, Amino Acid; hair follicle; promoter; chromosome 12q13; gene expression; Human; Hair; Keratin; Gene; DNA; Genetics; Isolation; Molecular biology
• ISSN: 0022-202X; 1523-1747
• DOI: 10.1046/j.1523-1747.2000.00910.x

Screening of an arrayed human genomic P1 artificial chromosome DNA library by means of the polymerase chain reaction with a specific primer pair from the human type II hair keratin hHb5 yielded two P1 artificial chromosome clones covering ≈300 kb of genomic DNA. The contig contained six type II hair keratin genes, hHb1–hHb6, and four keratin pseudogenes ψhHbA–ψhHbD. This hair keratin gene domain was flanked by type II epithelial keratins K6b/K6hf and K7, respectively. The keratin genes/pseudogene are 5–14 kbp in size with intergenic distances of 5–19 kbp of DNA and do not exhibit a single direction of transcription. With one exception, type II hair keratin genes are organized into nine exons and eight introns, with strictly conserved exon–intron boundaries. The functional hair keratin genes are grouped into two distinct subclusters near the extremities of the hair keratin gene domain. One subcluster encodes the highly related hair keratins hHb1, hHb3, and hHb6; The second cluster encodes the structurally less related hair keratins hHb2, hHb4, and hHb5. Reverse transcription–polymerase chain reaction shows that all hair keratin genes are expressed in the hair follicle. Pseudogene ψhHbD is also transcriptionally expressed, albeit with alterations in splicing and frameshift mutations, leading to premature stop codons in the splice forms analyzed. Evolutionary tree analysis revealed a divergence of the type II hair keratin genes from the epithelial keratins, followed by their segregation into the members of the two subclusters over time. We assume that the ≈200 kbp DNA domain contains the entire complement of human type II hair keratin genes.