Cloning and sequence analysis of porcine myoglobin cDNA

Porcine myoglobin cDNA clones have been isolated from a cDNA library prepared from enriched heart-myoglobin mRNA. Sequence analysis revealed 59 nucleotides (nt) in the 5'-untranslated, 462 nt in the amino acid (aa)-coding, and 590 nt in the 3'-untranslated regions. The myoglobin cDNA showed a high G + C content (60%). When the nt sequence of the porcine myoglobin cDNA is compared with those of seal and human myoglobin cDNAs deduced from the corresponding genomic myoglobin genes [Blanchetot et al., Nature 301 (1983) 732-734; Weller et al., EMBO J. 3 (1984) 439-446; Akaboshi, Gene 33 (1985) 241-249], a high degree of homology is observed in the 5'-untranslated region and in parts of the 3'-untranslated region, as well as in the coding region.     

The differential expression of cytosolic carbonic anhydrase in human hepatocellular carcinoma

Cytosolic carbonic anhydrases (CAs), including CAI, CAII and CAIII are present in normal hepatocytes. This study was aimed to investigate the expression status of CAs in hepatocellular carcinomas (HCC) and cholangiocellular carcinoma (CCC) and the role of tumor progression. The activity, protein expression pattern and messenger RNA of cytosolic CA were analyzed by CA activity analysis, immunoblot and RT-PCR in 60 human hepatocellular carcinomas and 10 human cholangiocellular carcinoma surgical specimens. The in situ distribution of CAI, CAII and CAIII in hepatocellular carcinomas tissues were analyzed by immunohistochemistry. The result showed that in each of 60 human hepatocellular carcinomas and 10 cholangiocellular carcinoma, CA activity and protein expression in tumor area was significantly lower than that of paired adjacent normal tissues (P < 0.01), and mRNA expressions in tumor areas were also reduced (P < 0.001). Furthermore, the immunohistochemical studies have further confirmed this reduction of CAI, CAII and CAIII protein expression in tumor areas. There was a statistically significant reduction in the expression of cytosolic CAII in poorly differentiated cancer (P < 0.001). Furthermore, the reduction of CAI, CAII and CAIII in HCC tumor areas was also revealed in this study and this reduction might promote tumor cell motility and contribute to tumor growth and metastasis.     

Nucleotide sequence of the chicken cardiac alpha actin gene: absence of strong homologies in the promoter and 3'-untranslated regions with the skeletal alpha actin sequence

The entire nucleotide sequence of the chicken cardiac alpha-actin (CC alpha A) gene has been determined. This is the first complete sequence of a cardiac actin gene that includes the promoter region, cap site, all the introns, and the polyadenylation site. The gene contains six introns, five of which interrupt the coding region at amino acids (aa) 41, 150, 204, 267, and 327. The first intron is in the 5'-noncoding region and is 438 bp in length. The CC alpha A gene encodes an mRNA of approx. 1400 bp with 5'- and 3'-untranslated region of 59 and 184 nucleotides (nt), respectively. Like the chicken skeletal alpha-actin gene, the CC alpha A gene has the codon for the aa cysteine between the initiator ATG and the codon for the N-terminal aspartic acid residue of the mature protein. There are no strong homologies (less than 13 consecutive nt) in the promoter or 3'-untranslated regions between the CC alpha A and chicken skeletal alpha-actin genes even though both are expressed in skeletal muscle during development. However, the 3'-untranslated region of the CC alpha A gene demonstrates significant sequence homology (76% over a 200-nt region) with the same region in the partial sequence of the human cardiac gene. The conservation of these sequence homologies between identical isoforms rather than the different alpha actin genes suggests these conserved regions may have a role in regulation rather than tissue-specific expression, as previously proposed.     

Cloning and nucleotide sequence of the murine hsp84 cDNA and chromosome assignment of related sequences

The nucleotide (nt) sequence of mouse 84-kDa heat shock protein (Hsp) cDNA has been determined using a combination of molecular cloning and oligodeoxynucleotide priming on poly(A) + RNA. The cDNA was 2.5 kb long, not including the poly(A) tail. It contained a 5' leader of about 94 nt that was G + C-rich, and a 243-nt 3'-untranslated region that was A + T-rich in the vicinity of the polyadenylation signal. Gene hsp84 codes for an acidic polypeptide of 724 amino acid (aa) residues. Mouse Hsp84 had 81% and 63% aa homology to Drosophila melanogaster Hsp82 and yeast Hsp90, respectively. The nucleotide sequence had 74% and 59% homology to Drosophila and yeast hsp sequences, respectively, in the coding regions of these genes. This homology did not extend to the 5' - and 3'-untranslated regions. Chromosomal analysis indicated that hsp84-related sequences are on at least three different chromosomes.     

Cloning, expression and sequence homologies of cDNA for human gamma enolase

The nucleotide sequence of the human gamma-enolase mRNA was determined from recombinant cDNA clones. The sequence spans 2273 bp and includes the complete coding region of 1299 bp, a 5'-noncoding region of 74 bp and a 897-bp-long 3'-noncoding region containing a variant polyadenylation signal (ATTAAA). The deduced amino acid (aa) sequence is 433 aa long and shows a 97% similarity with rat gamma-enolase. Both the 5'- and 3'-untranslated regions are similar (82% and 68%, respectively) to the analogous regions of the rat gamma-enolase gene, suggesting that a strong selective pressure operates on noncoding segments of gamma-enolase mRNAs. The size of the gamma-enolase mRNA expressed in human brain is 2.4 kb. A crosshybridizing 1.5-kb message is detected in human skeletal muscle which may be derived from the beta-enolase-coding gene.     

Immunocytochemical localization of carbonic anhydrase isozymes I, II, and III in rat skeletal muscle

Specific antisera were raised against the three carbonic anhydrase (CA) isozymes, CAI, CAII, and CAIII, and were used to determine the fiber distribution of these isozymes in skeletal muscle. Fiber types were determined by ATPase staining, and the CA isozymes were detected using a peroxidase-anti-peroxidase (PAP) technique. All three isozymes were present in type I fibers; CAII and CAIII were exclusive to these fibers, and CAI were also present in some small type 2A fibers.     

Molecular cloning and nucleotide sequence of a bovine alpha-lactalbumin cDNA

A cDNA clone for the bovine milk protein, alpha-lactalbumin (alpha LA), has been identified using a rat cDNA probe. The bovine cDNA clone is 703 nucleotides (nt) long, contains 8 nt of 5'-untranslated sequence and 269 nt of 3'-untranslated sequence. When compared with previously reported sequences, the bovine alpha LA mRNA sequence has 74% similarity with rat alpha LA mRNA, 79% similarity with human mRNA and 74% similarity with guinea pig mRNA.     

CpG islands in genes showing tissue-specific expression

Patterns of DNA methylation at CpG dinucleotides and their relations with gene expression are complex. Methylation-free CpG clusters, so-called HTF islands, are most often associated with the promoter regions of housekeeping genes, whereas genes expressed in a single-cell type are usually deficient in these sequences. However, in the human carbonic anhydrase (CA) gene family, both the ubiquitously expressed CAII and the muscle specific CAIII appear to have such CpG islands although erythrocyte-specific CAI does not. The CAII island is quantitatively more CpG rich than that of CAIII, with a CpG:GpC ratio of 0.94 compared with 0.82 for CAIII. Estimation of CpG:GpC ratios in the proximal-promoter regions of 44 vertebrate genes suggest that 40% of genes with tissue-specific or limited tissue distribution may show methylation-free CpG clusters in their promoter regions. In many cases the CpG:GpC ratio is less than that found in housekeeping genes and this may reflect variation in the interaction of CpG clusters with regulatory factors that define different patterns of tissue expression.     

Transport activity of the sodium bicarbonate cotransporter NBCe1 is enhanced by different isoforms of carbonic anhydrase

Transport metabolons have been discussed between carbonic anhydrase II (CAII) and several membrane transporters. We have now studied different CA isoforms, expressed in Xenopus oocytes alone and together with the electrogenic sodium bicarbonate cotransporter 1 (NBCe1), to determine their catalytic activity and their ability to enhance NBCe1 transport activity. pH measurements in intact oocytes indicated similar activity of CAI, CAII and CAIII, while in vitro CAIII had no measurable activity and CAI only 30% of the activity of CAII. All three CA isoforms increased transport activity of NBCe1, as measured by the transport current and the rate of intracellular sodium rise in oocytes. Two CAII mutants, altered in their intramolecular proton pathway, CAII-H64A and CAII-Y7F, showed significant catalytic activity and also enhanced NBCe1 transport activity. The effect of CAI, CAII, and CAII mutants on NBCe1 activity could be reversed by blocking CA activity with ethoxyzolamide (EZA, 10 μM), while the effect of the less EZA-sensitive CAIII was not reversed. Our results indicate that different CA isoforms and mutants, even if they show little enzymatic activity in vitro, may display significant catalytic activity in intact cells, and that the ability of CA to enhance NBCe1 transport appears to depend primarily on its catalytic activity.     

Mouse carbonic anhydrase III: Nucleotide sequence and expression studies

A cDNA for the mouse carbonic anhydrase, CAIII, has been isolated from a gt11 expression library. The cloned cDNA contains all of the coding region (777 bp) and both 5 untranslated (86-bp) and 3 untranslated (217-bp) sequences. The coding sequence shows 87% homology at the nucleotide level and 91% homology, when amino acid residues are compared, with human CAIII. Protein and mRNA analyses show that CAIII is present at low levels in cultured myoblasts and is abundant in adult skeletal muscle and in liver. The marked sex-related differences in CAIII distribution, described for rat liver, are not seen in the mouse. Restriction fragment length polymorphisms usingTaqI andPstI are described which distinguish betweenMus spretus andMus musculus domesticus.S. T. is supported by an MRC postgraduate training award.     

Rat liver carbonic anhydrase I is not sexually dimorphic but is estrogen repressible

Carbonic anhydrase (CA) isozymes CAII and CAIII are known to exhibit sexual dimorphism in rat liver, and the levels o f these isozymes are affected by sex hormones. In this paper we show that the isozyme CAI is present at low levels in rat liver, with no difference in concentration between male and female rats. Estrogen and diethylstilbestrol reduce CAI levels in both sexes.     

Rat aldolase A messenger RNA: the nucleotide sequence and multiple mRNA species with different 5'-terminal regions

The nucleotide sequence of aldolase A mRNA in rat skeletal muscle was determined using recombinant cDNA clones and a cDNA synthesized by primer extension. The sequence is composed of 1343 nucleotides (nt) except for the poly(A) tail. Based on the sequence analysis we have deduced an open reading frame with 363 amino acids (aa) (Mr 39134). The sequence suggests several nt polymorphisms in the mRNA population, one of which causes an aa change. The determined sequence of rat aldolase A mRNA was compared with the published ones of rabbit aldolase A or rat aldolase B mRNAs. The homology between rat and rabbit aldolase A mRNA sequences is greater than that between rat aldolase A and B mRNA sequences. Multiple aldolase A mRNAs having different Mrs were detected in the various tissues, and appeared to be expressed in a tissue-specific manner. Further analysis suggests that differences in mRNA length are due to differences in the 5'-noncoding terminal region.     

Characterisation of cDNA clones for rat muscle carbonic anhydrase III

cDNA clones for rat muscle carbonic anhydrase III have been isolated from a gt-11 library and sequenced. Comparison with human CAIII cDNA showed about 90% homology to rat. The rat clones were used to estimate mRNA from liver and muscle on Northern blots and showed that the sexual dimorphism of CAIII in rat liver relates to a difference in mRNA levels.     

Human mitochondrial ATP synthase: cloning cDNA for the nuclear-encoded precursor of coupling factor 6

Coupling factor 6 (F6) is a component of mitochondrial ATP synthase which is required for the interactions of the catalytic and proton-translocating segments. A human fetal muscle cDNA clone encoding this protein was isolated by screening a lambda gt10 library with oligodeoxyribonucleotide probes. The 497-bp F6 cDNA included a 96-bp segment that delineated a presequence of 32 amino acids (aa) in the precursor protein, and 140 bp of 3'-untranslated sequence. The remainder of the cDNA sequence coded for a mature human F6 protein of 76 aa. The deduced primary aa sequence showed 81% homology to that of bovine F6, differing in 14 aa. Almost all of these aa substitutions were conservative and comparison of the hydropathy profiles revealed a similar pattern.     

Characterisation of an mRNA encoding a human ribosomal protein homologous to the yeast L44 ribosomal protein

We describe the isolation and characterisation of a full-length cDNA sequence (pZH-21) of a human ribosomal protein (rp) mRNA isolated from a cDNA library constructed from the human ZR-75-1 mammary tumour cell-line. The predicted protein is highly basic and shows 72% homology at the amino acid (aa) level with yeast rp L44. Comparative RNA blotting of ZR-75-1 poly(A)+ RNA isolated from cells cultured in the presence of the anti-oestrogen tamoxifen demonstrates the presence of a number of mRNA species whose concentration is elevated co-ordinately 5-6-fold in the presence of 17beta-oestradiol. Insulin in the presence of tamoxifen, also enhanced rp mRNA levels suggesting increased levels are a reflection of cell proliferation as opposed to specific hormonal regulation. Genomic analysis demonstrates the presence of a family of related human sequences, and homology with rat and guinea pig rp genes, but not yeast DNA. The conservation of rp aa sequence, in the absence of detectable homology at the nucleotide (nt) level, points to an important common functional role of the L44 protein in ribosome structure and function in man and yeast.     

Sequence conservation in the 3'-untranslated regions of neurone-specific enolase, lymphokine and protooncogene mRNAs

The C-terminal protein-coding and the entire 3'-untranslated regions of a cDNA corresponding to human neurone-specific enolase mRNA have been sequenced. The 3'-untranslated region is 892 bases long and shows a high degree of homology with the 3'-untranslated region of rat neurone-specific enolase mRNA. This sequence conservation is not seen in non-neuronal enolase mRNAs. Features of the conserved sequence include an A-rich region approx. 250 bases from the stop codon at a point corresponding to the polyadenylation signal site in non-neuronal enolase mRNA, and a repeating ATTT sequence. This unusual motif in eukaryotic mRNAs has previously been reported in the 3'-untranslated regions of lymphokine and protooncogene mRNAs.     

The nucleotide sequence of a cDNA clone containing the entire coding region for mouse X-chromosome-linked phosphoglycerate kinase

A clone containing cDNA for X chromosome-linked phosphoglycerate kinase (PGK-1) was isolated from a mouse myeloma cDNA library. The nucleotide (nt) sequence of the cDNA has been determined, and the amino acid (aa) sequence of the enzyme thereby deduced. At the nt level, the coding region of mouse PGK cDNA has 93% homology with human X-linked cDNA and 60% homology with the yeast gene. Mouse PGK-1 protein contains 416 aa and is 98%, 96% and 64% homologous with human, horse, and yeast enzyme sequences, respectively.     

Thrombospondin II: partial cDNA sequence, chromosome location, and expression of a second member of the thrombospondin gene family in humans.

A novel form of human thrombospondin was identified during the screening of a human fibroblast cDNA library. We report the cDNA sequence for 1.8 kb of the 3' end of the cDNA, plus an additional 937 bp of 3'-untranslated sequence. The translated sequence reveals a high degree of similarity to thrombospondin I. The homology ranges from 56 to 80% for different regions within the two proteins. The repeating segments of amino acid sequence identified in thrombospondin I were found to be conserved in thrombospondin II. The new form of thrombospondin hybridizes to a 7.5-kb message by Northern analysis. The THBS2 gene is located at the distal long arm of chromosome 6 at 6q27. The gene is transcribed in fibroblasts, smooth muscle cells, and an osteosarcoma cell line, at levels somewhat lower than that of thrombospondin I. Umbilical vein endothelial cells do not transcribe thrombospondin II under the conditions of this study. These findings suggest that previous studies of thrombospondin function need to be reassessed to identify the functions specific to each molecule.