RESUMEN
Hyaluronan (HA) is a linear glycosaminoglycan of the vertebrate extracellular matrix that is synthesized at the plasma membrane by the HA synthase (HAS) enzymes HAS1, -2 and -3. The regulation of HA synthesis has been implicated in a variety of extracellular matrix-mediated and pathological processes, including renal fibrosis. We have recently described the genomic structures of each of the human HAS genes. In the present study, we analyzed the HAS2 promoter region. In 5'-rapid amplification of cDNA ends analysis of purified mRNA from human renal epithelial proximal tubular cells, we detected an extended sequence for HAS2 exon 1, relocating the transcription initiation site 130 nucleotides upstream of the reference HAS2 mRNA sequence, GenBank accession number NM_005328. A luciferase reporter gene assay of nested fragments spanning the 5' terminus of NM_005328 demonstrated the constitutive promoter activity of sequences directly upstream of the repositioned transcription initiation site but not of the newly designated exonic nucleotides. Using reverse transcription-PCR, expression of this extended HAS2 mRNA was demonstrated in a variety of human cell types, and orthologous sequences were detected in mouse and rat kidney. Alignment of human, murine, and equine genomic DNA sequences upstream of the repositioned HAS2 exon 1 provided evidence for the evolutionary conservation of specific transcription factor binding sites. The location of the HAS2 promoter will facilitate analysis of the transcriptional regulation of this gene in a variety of pathological contexts as well as in developmental models in which HAS2 null animals have an embryonic lethal phenotype.
Asunto(s)
Glucuronosiltransferasa/genética , Regiones Promotoras Genéticas/genética , Animales , Secuencia de Bases , Línea Celular , Cartilla de ADN , Etiquetas de Secuencia Expresada , Glucuronosiltransferasa/química , Humanos , Hialuronano Sintasas , Riñón , Ratones , Datos de Secuencia Molecular , Ratas , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Alineación de Secuencia , Homología de Secuencia de Ácido Nucleico , Células Tumorales CultivadasRESUMEN
The glycosaminoglycan (GAG) hyaluronan (HA) is a key component of the vertebrate extracellular matrix (ECM) and is synthesised by the HA synthase (HAS) enzymes HAS1, HAS2 and HAS3 at the plasma membrane. Accumulating evidence emphasises the relevance of HA metabolism in an increasing number of processes of clinical interest including renal fibrosis and peritoneal mesothelial wound healing. In the present study, the genomic sequences and organisation of the genes encoding the human HAS isoforms were deduced, in silico, from reference cDNA and genomic sequence data. These data were confirmed in vitro by sequencing of PCR-amplified HAS exons and flanking genomic sequences, comparison with sequence data for the corresponding murine Has orthologues, rapid amplification of 5' cDNA ends analysis and luciferase reporter assays on putative proximal promoter sequences. The HAS1 gene comprised five exons, with the translation start site situated 9bp from the 3' end of exon 1. In contrast, the genomic structures for HAS2 and both HAS3 variants spanned four exons, exon 1 forming a discrete 5'-untranslated region (5'-UTR) and the translation start site lying at nucleotide 1 of exon 2. Dinucleotide microsatellite loci were identified in intron 1 of HAS1 and HAS2, and immediately upstream of the HAS3 gene and their utility as linkage markers demonstrated in genomic DNA (gDNA) studies. We thus present a comprehensive resource for mutation detection screening of all HAS exons and/or linkage analysis of each HAS gene in a variety of disorders for which they are attractive candidates.