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KERATIN 35, TYPE I; KRT35

KERATIN 35, TYPE I; KRT35

Alternative titles; symbolsK35KA30KERATIN, HAIR, ACIDIC, 5; KRTHA5KERATIN, HARD, TYPE I, 5; HA5HGNC Approved Gene Symbol: KRT35Cytogenetic location: 17q21.2 ...

Alternative titles; symbols

  • K35
  • KA30
  • KERATIN, HAIR, ACIDIC, 5; KRTHA5
  • KERATIN, HARD, TYPE I, 5; HA5

HGNC Approved Gene Symbol: KRT35

Cytogenetic location: 17q21.2 Genomic coordinates (GRCh38): 17:41,476,709-41,481,150 (from NCBI)

▼ Description
See KRTHA1 (601077) for general information on hair keratins.

▼ Cloning and Expression
Rogers et al. (1996) identified the KRTHA5 gene, which they called HA5, while studying the HA2 (KRTHA2; 602760) genomic sequence. Using the partial HA5 genomic fragment to screen a human scalp cDNA library, the authors isolated an HA5 cDNA. A comparison of the genomic and cDNA sequences revealed the presence of an intron in the 3-prime noncoding region. Together with the 6 conserved introns expected in the region encoding the alpha-helical domain, the HA5 gene has 7 introns. The predicted 425-amino acid HA5 protein contains a C-terminal domain with 8 cysteine and 10 proline residues. Its N-terminal domain lacks sequence homology with the N-terminal domains of HA1 (KRTHA1), HA3A (KRTHA3A; 602761), HA3B (KRTHA3B; 602762), and HA4 (KRTHA4; 602763), all of which are closely conserved in length and sequence. Northern blot analysis detected a 1.8-kb HA5 transcript in human scalp but not in hairless epidermis. In situ hybridization detected HA5 transcripts mainly in supramatricial cells and lowermost cortical cells of the hair bulb, indicating that HA5 is expressed early in hair morphogenesis; transcripts were not detected in the cuticle. See Langbein et al. (1999) for additional information on the expression pattern of the KRTHA5 gene in the hair follicle.

Rogers et al. (1998) reported that the deduced KRTHA5 protein has 426 amino acids.

▼ Mapping
Rogers et al. (1996) located the HA5 gene 8 kb upstream of the HA2 gene on 17q12-q21 and found that the 2 genes are oriented in the same transcriptional direction.

Rogers et al. (1998) isolated and characterized 2 overlapping human PAC clones that cover 190 kb on 17q12-q21 and contain 9 type I hair keratin genes, 1 transcribed hair keratin pseudogene, and 1 orphan exon. The order of the genes is 5-prime--KRTHA6 (604540)--KRTHA5--KRTHA2--orphan exon--KRTHA8 (604542)--KRTHA7 (604541)--pseudogene--KRTHA1--KRTHA4--KRTHA3B--KRTHA3A--3-prime. The hair keratin genes range in size from 4.2 to 7.5 kb, and the genes are separated from each other by 5.5 to 18.4 kb; all are located within about 140 kb. Except for KRTHA5, which has 8 exons, all of the genes contain 7 exons. Each gene is transcribed from the 5-prime to 3-prime direction. Based on sequence homologies, the genes can be grouped into 3 subclusters of tandemly arranged genes. One subcluster, group A, consists of KRTHA1, KRTHA3A, KRTHA3B, and KRTHA4, which share 89% overall amino acid identity. A second subcluster, group B, contains KRTHA7 and KRTHA8, as well as the hair keratin pseudogene, which the authors called HAA. The functional hair keratins and hypothetical HAA hair keratin share approximately 81% overall amino acid identity. The third subcluster, group C, consists of the structurally less related hair keratins KRTHA2, KRTHA5, and KRTHA6, which share about 70% amino acid identity.

Tags: 17q21.2