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The enzyme steroid 5 alpha-reductase catalyzes the conversion of testosterone into the more powerful androgen, dihydrotestosterone. We previously described the cloning of rat and human cDNAs that encode steroid 5 alpha-reductase and their expression in oocytes and cultured cells. Here, we report the isolation, characterization, and chromosomal mapping of two human steroid 5 alpha-reductase genes. One gene (symbol SRD5A1) is functional, contains five exons separated by four introns, and maps to the distal short arm of chromosome 5. Two informative restriction fragment length polymorphisms are present in exons 1 and 2 of this gene. A second gene (symbol SRD5AP1) has all of the hallmarks of a processed pseudogene and was mapped to the q24-qter region of the X chromosome. In the mouse, a single steroid 5 alpha-reductase gene (Srd5 alpha-1) is linked to Xmv-13 on chromosome 13.

Subunit Vb of mammalian cytochrome c oxidase (COX; EC 1.9.3.1) is encoded by a nuclear gene and assembled with the other 12 COX subunits encoded in both mitochondrial and nuclear DNA. We have cloned the gene for human COX subunit Vb (COX5B) and determined the exon-intron structure by both hybridization analysis and DNA sequencing. The gene contains five exons and four introns; the four coding exons span a region of approximately 2.4 kb. The 5' end of the COX5B gene is GC-rich and contains many HpaII sites. Genomic Southern blot analysis of human DNA probed with the human COX Vb cDNA identified eight restriction fragments containing COX Vb-related sequences that were mapped to different chromosomes with panels of human x Chinese hamster somatic cell hybrids. Because only one of these fragments hybridized with a 210-bp probe from intron 4, we conclude that there is a single expressed gene for COX subunit Vb in the human genome. We have mapped this gene to chromosome 2, region cen-q13.

Histidine-rich calcium binding protein (HRC) is a luminal sarcoplasmic reticulum (SR) protein of 165 kDa identified by virtue of its ability to bind 125 I-labeled lowdensity lipoprotein with high affinity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Hofmann et al., J. Biol. Chem. 264: 8260–8270, 1989). Its role in SR function is unknown. In this report, the gene encoding human HRC was localized to human chromosome 19 and mouse chromosome 7 by hybridization of a human HRC cDNA fragment to a panel of somatic cell hybrids. Known synteny between a portion of human chromosome 19 and a portion of mouse chromosome 7 and in situ hybridization of a biotin-labeled HRC probe to human chromosomes suggest a localization to a region corresponding to 19q13.3. The locus for myotonic dystrophy resides in the region 19q13.2–13.3. Therefore, we considered HRC , a muscle-specific gene, to possibly represent a “candidate gene” for myotonic muscular dystrophy. As a first step toward localizing HRC in relation to the myotonic dystrophy locus, we report the cloning of the human HRC gene, its intron-exon organization, and characterization of several informative polymorphisms to be used in future linkage studies in families with myotonic dystrophy. Of particular interest is an Alu -associated poly-d(GA) sequence located in an intron in the middle of the gene, and two stretches of acidic amino acids in the coding region of exon 1 that vary in length among different individuals.

We have cloned and characterized the mouse gene, P 0 , that encodes the predominant protein of peripheral myelin. Similar to the rat gene, the mouse P 0 gene is encoded by six exons that span about 7 kb of DNA. The DNA sequence of the mouse gene is highly homologous with the rat gene, including the regions believed to be important in transcriptional control. Furthermore, the P 0 protein appears well conserved throughout evolution. The gene was mapped to mouse chromosome 1 by Southern analysis of a Chinese hamster × mouse somatic cell hybrid panel. Several polymorphic restriction enzyme sites were identified within the P 0 locus. Recombinant inbred strain mapping has linked the P 0 gene to Ly-9/Ly-17/Sap in a region corresponding to band 1H3.

We have isolated and sequenced the gene encoding the human embryonic/atrial myosin alkali light chain isoform ( MLC-1 emb A ). The gene is split into seven exon by six introns; the last exon, as in all MLC isoform genes sequenced to date, is completely 3′ untranslated sequence. Comparison of the MLC-1 emb A isoform gene with the other MLC-1 genes showed that the exonintron arrangement of the human MLC-1 emb A isoform gene is analogous to that of the other MLC-1 type isoform genes. We have also mapped the human MLC-1 emb A isoform gene to the long arm of chromosome 17; the corresponding mouse gene has been mapped to chromosome 11. This gene, together with a number of others such as the collagen(I) α1, galactokinase, and thymidine kinase genes, is part of the largest syntenic group between mouse and man.

Aldehyde dehydrogenases are a group of enzymes responsible for catalyzing the conversion of numerous aldehydes to their corresponding acids. These enzymes play a major role in the detoxification of alcohol-derived acetaldehydes and in the metabolism of corticosteroids, biogenic amines, neurotransmitters, and lipid peroxidation. ALDH activities are found in most tissues, with the highest activity in the liver. Five human liver ALDH isozymes, ALDH1, 2, 3, 4, and {gamma}-butyrylaldehyde dehydrogenase ({gamma}-ABDH), have been purified and characterized, and one isozyme, ALDH5, has been identified by using a 29-nucleotide probe that is conserved in ALDH1 and ALDH2 for cDNA library screening. Several other isozymes from other tissues have also been reported. Genes for ALDH3 and ALDH5 have been previously localized to chromosomes 17 and 9, respectively. Here we report the regional assignment of these two loci. 17 refs., 1 fig.

We recently purified and cloned the gene for a DNA structure-specific endonuclease, FEN-1, from murine cells. The murine protein recognizes 5{prime} DNA flap structures that have been proposed in DNA replication, repair, and recombination. Here, we report the sequence of the human FEN1 gene. The translated sequence is identical to peptide sequence obtained from maturation factor-1, which is 1 of the 10 essential proteins for cell-free DNA replication. The human protein has the same structure-specific DNA endonuclease activity as the murine protein. Two human chromosomal hybridization signals, 11q12 and 1p22.2, were observed by FISH analysis using human genomic clones homologous to the mouse Fen-1 gene. The localization on human 11q12 was confirmed using radiation-reduced hybrids. The mouse Fen-1 gene is assigned to chromosome 19 based on somatic cell hybrids. The significance of these FEM gene localizations in human and mouse is discussed. 19 refs., 3 figs., 1 tab.

Aldehyde dehydrogenase isozymes have been suggested to play a major role in the detoxification of aldehydes generated by alcohol metabolism and lipid peroxidation. We previously cloned and characterized four human nonallelic ALDH genes encoding different isozymes. The existence of an unique ALDH isozyme in human saliva and its polymorphism has been demonstrated previously. In this paper, we describe the cloning, characterization, and chromosomal mapping of an aldehyde dehydrogenase gene ( ALDH6 ) expressed in the human salivary gland. The cloned ALDH6 cDNA is 3457 bp in length and contains an open reading frame encoding 512 amino acid residues. The deduced amino acid sequence showed that ALDH6 is larger than the human liver ALDH1 by 11 amino acid residues at the N-terminal, and the degree of identity between the two isozymes is 70% with an alignment of 500 amino acid residues. The human ALDH6 gene spans about 37 kb and consists of 13 exons. The putative TATA and CCAAT boxes and Sp1 binding sites are found in the 5′ upstream region of the gene. Northern blot analysis demonstrated that the ALDH6 gene is expressed at low levels in many tissues and at higher levels in salivary gland, stomach, and kidney. The ALDH6 gene was assigned to chromosome 15q26 using fluorescence in situ hybridization.

Moesin is a member of a recently discovered family of closely related proteins that includes ezrin, radixin, and merlin. It is widely expressed in different tissues and cells and has been localized to filopodia and other membranous protrusions that are important for cell-cell recognition and signaling and cell movement. Here, we have localized the coding gene (MSN) to Xq11.2-q12 by Southern and Western blot analyses of Chinese hamster × human somatic cell hybrids and by fluorescence chromosomal in situ hybridization. Moesin-like sequences were identified on chromosomes 5 and 6. The murine Msn locus was mapped to the X chromosome as well by studying a rodent × mouse hybrid panel. The structure of the human moesin gene has been determined. The 12 exons are distributed over >30 kb, and the exon/intron junctions demarcate individual highly conserved domains. Primer extension analysis revealed two major start transcription sites, 184 and 133 bp upstream of the initiation codon. The 5′-flanking region is GC-rich, lacks a TATA box, and contains four SP1 and one AP1 binding sites.

Cellular cholesterol metabolism is regulated primarily through sterol-mediated feedback suppression of the activity of the low-density lipoprotein receptor and several enzymes of the cholesterol biosynthetic pathway. We previously described the cloning of a rabbit cDNA for the oxysterol-binding protein (OSBP), a cytosolic protein of 809 amino acids that may participate in these regulatory events. We now use the rabbit OSBP cDNA to clone the human OSBP cDNA and 5' genomic region. Comparison of the human and rabbit OSBP sequences revealed a remarkably high degree of conservation. The cDNA sequence in the coding region showed 94% identity between the two species, and the predicted amino acid sequence showed 98% identity. The human cDNA was used to determine the chromosomal localization of the OSBP gene by Southern blot hybridization to panels of somatic cell hybrid clones containing subsets of human or mouse chromosomes and by RFLP analysis of recombinant inbred mouse strains. The OSBP locus mapped to the long arm of human chromosome 11 and the proximal end of mouse chromosome 19. Along with previously mapped genes including Ly-1 and CD20, OSBP defines a new conserved syntenic group on the long arm of chromosome 11 in the human and the proximal end of chromosome 19 in the mouse.

Mitochondrial RNA-processing endoribonuclease (RNAase MRP) has the capacity to cleave mitochondrial RNA complementary to the light strand of the displacement loop at a unique site. The enzyme is a ribonucleoprotein whose RNA component is a nuclear gene product. The 5′ flanking region of the primary transcript has control elements characteristic of RNA polymerase II transcription, and the coding region has features of RNA polymerase III transcription signals. The RNA associated with RNAase MRP is the first known RNA encoded by a single-copy gene in the nucleus and believed to be imported into mitochondria. The gene (RMRP) for this RNA component of RNAase MRP was assigned to human chromosome 9 and mouse chromosome 4 by Southern blot analyses of 11 human × rodent hybrids and 11 mouse × rodent hybrids with probe pHM1.0 and probe pSP270, respectively. In situ hybridization of probe pHSTU300 to normal human chromosomes revealed 29 of 100 cells with label on 9p and 9.6% of 302 silver grains located at 9p21-p12.