Human hepatic triglyceride lipase: cDNA cloning, amino acid sequence and expression in a cultured cell line

By immunoscreening of a human cDNA expression library and hybridization of colonies, four partially overlapping cDNA clones of human hepatic triglyceride lipase (HTGL) mRNA were isolated. The clones included the complete coding sequence, the 3'- and at least part of the 5'-untranslated region. The length of the composite HTGL cDNA segment (1.7 kb) was consistent with the size of the mRNA identified in an established human hepatoma cell line. DNA-sequence analysis of cDNAs of partially unspliced mRNAs, and of cloned genomic DNA indicated that the HTGL coding sequence comprises at least six exons. As predicted from the cDNA, the unprocessed HTGL protein has a molecular weight of 56, three potential glycosylation sites, and a signal peptide of 23 amino acids. Sequence comparison with cDNA of other lipases, including rat hepatic lipase, revealed 30%-75% protein-sequence homology. The data establish that HTGL is a secretory protein produced in the hepatocyte, and that its synthesis can be continued in permanent cell lines of hepatoma origin. Our studies also showed that HTGL is another member of a lipase gene family which has interfacial binding sites and possibly other functional domains in common.

Replication strategy of human hepatitis B virus

To study the replication strategy of the human hepatitis B virus, the 5' end of the RNA pregenome and the initiation sites of DNA plus and minus strands have been mapped. The RNA pregenome was found to be terminally redundant by 120 nucleotides; it is initiated within the pre-C region and may also function as mRNA for synthesis of the major core protein and the hepatitis B virus reverse transcriptase. The hepatitis B virus DNA minus strand is initiated within the direct repeat sequence DR1, it contains a terminal redundancy of up to eight nucleotides, and its synthesis does not require any template switch. The DNA plus strand is primed by a short oligoribonucleotide probably derived from the 5' end of the RNA pregenome, and its synthesis is initiated close to the direct repeat sequence DR2. For its elongation to pass the discontinuity in the DNA minus strand an intramolecular template switch occurs using the terminal redundancy of this template. Thus, the route of reverse transcription and DNA replication of hepatitis B viruses is fundamentally different from that of retroviruses.

Sarcolemmal Na-Ca exchange and sarcoplasmic reticulum calcium uptake in developing chick heart

Ontogenetic changes in calcium transport mediated by the sarcolemmal Na-Ca exchanger and by the sarcoplasmic reticulum calcium pump were studied in crude membranes from chick heart. Transport activities were evaluated per mass of membrane protein and heart tissue. Relative to unit heart mass Na-Ca exchange activity increases linearly from embryonic day 4 to day 10 of newborn stage. The overall increase is about 20-fold. An excellent correlation exists between activity of sodium gradient-induced calcium uptake and ouabain-sensitive (Na,K)-ATPase in crude membranes of embryonic, newborn and adult hearts. In the same membrane preparations active calcium uptake into vesicles of sarcoplasmic reticulum increases about 3-fold from embryonic day 4 to embryonic day 7, and then increases continuously until day 20. This is followed by a 3-fold elevation in reticular calcium accumulation at hatching on day 21. Maximal sarcoplasmic reticulum calcium transport activity reached at day 10 after hatching is 40- to 50-fold greater than activity values at embryonic day 4. In adult hearts the activities of both Na-Ca exchange and reticular calcium uptake drop to levels characteristic for the late embryonic period. This comparative study of sarcolemmal sodium gradient-dependent calcium flux and reticular calcium sequestration demonstrates that during chick heart differentiation the two calcium transport systems do not develop in parallel. Na-Ca exchange appears to play a greater role in calcium control of embryonic as compared to newborn and adult hearts. By contrast, the contribution of sarcoplasmic reticulum calcium transport to cardiac calcium movements becomes more predominant during and after hatching.

A recombinant Chinese hamster ovary cell line containing a 300-fold amplified tetramer of the hepatitis B genome together with a double selection marker expresses high levels of viral protein

A new series of double-selection plasmids containing recombinant genes expressing the neomycin phosphotransferase (NEO) of transposon Tn5 and mouse dihydrofolate reductase (DHFR) in mammalian cells is described. Activity of the recombinant DHFR gene varied more than 50-fold, depending on the location of the simian virus 40 72 base-pair repeat or enhancer, which is part of the promoter of the NEO unit. A NEO-DHFR module with the enhancer located at the 3' end of the DHFR gene was inserted into a plasmid containing four tandem head-to-tail copies of the hepatitis B virus (HBV) genome and the new plasmid was used to transform DHFR- Chinese hamster ovary cells. In one of the cell lines obtained, an unrearranged copy of the HBV tetramer could be amplified 300-fold by increasing selective pressure with methotrexate, resulting in a proportional increase of the synthesis of HBV surface antigen. Four different mRNAs detected in the amplified cell line probably encode HBV core protein, pre-S and surface antigens, and the X protein. As a result of the DNA amplification, synthesis of HBV proteins is no longer restricted to resting cells. Integrated plasmid sequences appear to be stable during the amplification process.

Putative reverse transcriptase intermediates of human hepatitis B virus in primary liver carcinomas

Nucleocapsid-pol fusion proteins have been detected by serological screening hepatocellular carcinoma tissues that contain hepatitis B virus (HBV) DNA. The existence of these fusion proteins suggests that HBV may synthesize its reverse transcriptase in a fashion analogous to the way that retroviruses synthesize and process a precursor. The accumulation of HBV reverse transcriptase intermediates in tumorous tissues and not in other tissues may be related to the absence of viral core particles and possibly contributes to tumor development.

Comparative analysis of phospholamban phosphorylation in crude membranes of vertebrate hearts

Phospholamban, a sarcoplasmic reticulum phosphoprotein, is present in the hearts of mammalian, avian, amphibian, and fish species. Phylogenetic changes are indicated by marked differences among species in cardiac phospholamban content and by the absence of Ca2+/calmodulin-dependent phospholamban phosphorylation at an early developmental stage.

Determination of HBV DNA by a simplified method of spot hybridization

Molecular hybridization was employed to detect HBV DNA in sera of patients with acute or chronic hepatitis, by a simplified version of the spot hybridization technique. HBV DNA was found in 21 out of 50 sera obtained in acute hepatitis B. Determination of HBV DNA was negative in sera of patients with hepatitis A, Epstein-Bar virus infections or other HBsAg-negative liver diseases. There was no cross-hybridization between HBV DNA and sera of patients with non-A, non-B hepatitis.

[A serological criterion for Bechterew's disease. Demonstration of a new antibody specificity with polytene chromosomes]

A new antibody reacting with an antigen from polytene chromosomes of Drosophila melanogaster has been found in serum of patients with Bechterew's disease. This antigen-antibody system differs from other nuclear antibodies (anti-RNP, anti-Sm, anti-Ha/SS-B) in that it is not detectable by counter-immunoelectrophoresis. The antibody could be detected in 24 out of 62 Morbus Bechterew sera in which the antibody did not strictly correlate with the appearance of HLA-B27 antigen. The new antibody specificity is a specific serological finding in patients with Bechterew's disease and is therefore suitable for use as a diagnostic, and perhaps also as a prognostic test for this type of spondylarthritis till now assumed to be seronegative.

Structure of human ferritin light subunit messenger RNA: comparison with heavy subunit message and functional implications

Ferritin has a protein shell of 5 X 10(6) Da consisting of 24 subunits of two types, a heavier (H) chain of 21,000 Da and a lighter (L) chain of 19,000 Da. A cDNA clone of the messenger for the L subunit has been isolated from a human monocyte-like leukemia cell line. The clone contains an open reading frame of 522 nucleotides coding for an amino acid sequence matching 97% of the published sequence of human liver ferritin L subunit determined by sequenator, but it corresponds to only 55% of the reported amino acid sequence of a human liver H-subunit clone. Nevertheless, computer analysis of the subunit conformations predicted from the open reading frames of the L and H clones shows that most of the amino acid differences are conservative and would allow both subunits to form the five alpha-helices and beta-turns established by x-ray crystallography for horse spleen ferritin subunits. This suggests that L and H subunits are structurally interchangeable in forming an apoferritin shell. The 5' untranslated region of our human ferritin L clone has considerable homology with that of the rat liver ferritin L clone in the region immediately upstream from the initiator codon, notably showing an identical sequence of 10 nucleotides at the same position in both subunit clones that may participate in regulating the known activation of ferritin mRNA after iron administration. Extensive homology, including several blocks of nucleotides, was identified between the 3' untranslated regions of the human and rat L clones. The common structural features of the H and L subunits lead us to conclude that they have diverged from a single ancestral gene.

Comparative sequence analysis of duck and human hepatitis B virus genomes

We have cloned and sequenced an infectious, functionally active genome of a duck hepatitis B virus (DHBV). It is 3,021 base pairs (bp) in length and shows little DNA sequence homology to the genome of human hepatitis B virus (HBV). However, the amino acid sequences of predicted viral gene products are similar between DHBV and HBV, and the genome organization present in DHBV reflects that of HBV. As in the mammalian virus the long minus strand of the DHBV genome encodes three long overlapping reading frames designated as P, S, and C. The fourth open reading frame, termed X, is absent in DHBV. A comparison with a sequence of a second DHBV isolate [Mandart et al, Journal of Virology 49:782-792, 1984] revealed a nucleotide sequence variation of 5.6% and confirmed the presented overall gene organization of DHBV.

Transcripts and the putative RNA pregenome of duck hepatitis B virus: implications for reverse transcription

Duck hepatitis B virus (DHBV) is a DNA virus that replicates by reverse transcription. We have examined transcripts of DHBV to elucidate mechanisms of gene expression and replication. Three major transcripts were characterized and related to the expression of the genes for the core antigen (DHBcAg), the surface antigen (DHBsAg), and the pre-S/DHBs protein, respectively. They are unspliced and overlap partially since they start at different promoter sites, but they terminate near a common polyadenylation signal. The messenger RNA related to DHBcAg expression is the only major transcript of more than genome length and therefore also represents the putative template for reverse transcription (pregenome). Its structure predicts a strategy of replication of hepatitis B viruses different from that of retroviruses.

[Integrated and nonintegrated hepatitis B virus DNA in liver tissue]

Liver tissue was taken in eight patients with virus hepatitis B and one patient with liver carcinoma by biopsy, as well as in seven other patients at post mortem. HBV-DNA was measured in these tissue specimens by hybridization. In four out of eight patients who had had biopsy, HBV-DNA could be found; in two patients it was present in integrated form. The same was true for the tumor tissue stemming from the patient with liver carcinoma. In five out of eight liver tissue specimens taken at post mortem HBV-DNA could be demonstrated as well; it was integrated into the host genom in two cases. It may be important to find out in patients with chronic hepatitis virus infection, if HBV-DNA is present in free or integrated form before antiviral treatment is considered.

Determination of HBV DNA in serum in a case of needlestick hepatitis

HBV DNA in serum was determined by modified spot hybridization. A nurse of the dialysis staff was inoculated via needlestick with blood of a HBsAg-positive hemodialysis patient, who had 2000 pg HBV DNA per milliliter serum. After insufficient passive immunization the nurse developed transient anicteric hepatitis B. HBV DNA was positive in sera of the recipient before and at the beginning of the elevation of transaminases.

Cloned duck hepatitis B virus DNA is infectious in Pekin ducks

Approximately 10% of German-bred Pekin ducks were found to be chronically infected with duck hepatitis B virus (DHBV). The genomes of three German DHBV isolates analyzed were closely related but showed substantial restriction site polymorphism compared with U.S. isolates. We tested the infectivity of three sequence variants of cloned DHBV DNA by injecting them into the liver of virus-free ducklings. Most of these animals injected with double-stranded closed-circular or plasmid-integrated dimer DHBV DNA developed viremia, demonstrating the infectivity of all three cloned DHBV DNA variants. The cloned viruses produced were indistinguishable from those from naturally infected animals, implying that our experimental approach can be used to perform a functional analysis of the DHBV genome.

A new sensitive method for qualitative and quantitative assay of neomycin phosphotransferase in crude cell extracts

A general method is described for the detection and quantification of low amounts of neomycin phosphotransferase in crude cell extracts. The assay is based on the electrophoretic separation of the enzyme from other interfering proteins and detection of its enzymatic activity by in situ phosphorylation of the antibiotic kanamycin. Both kanamycin and [gamma-32P]ATP acting as substrates are embedded in an agarose gel placed on the polyacrylamide gel containing the separated proteins. After the enzymatic reaction, the phosphorylated kanamycin is transferred to P81 phosphocellulose ion exchange paper and the radiolabeled kanamycin is visualised by autoradiography. With this method 1 ng of active enzyme can easily be detected. Both prokaryotic and eukaryotic cell extracts can be examined, and changes in the size of enzymatically active proteins can be determined.

[Anti-HBc IgM in acute and chronic hepatitis B virus infection]

Hepatitis B core antigen (HBcAg) synthesized in E. coli was used for determination of immunoglobulin M class-specific antibodies against HBcAg. It was found that 98% of cases with acute hepatitis B surface antigen (HBsAg) positive hepatitis type B were anti-HBc immunoglobulin M (IgM) positive. Atypical hepatitis B was detected in 33% of anti-HBc-positive HBsAg-negative cases with acute hepatitis. Anti-HBc IgM was positive for 6 months in acute resolving hepatitis type B, whereas cases resulting in chronic hepatitis B remained anti-HBc IgM-positive for up to 900 days. Chronic HBsAg carriers with severe liver disease had anti-HBc IgM more often than individuals with minor liver damage; 83% of HBsAg-positive liver cirrhoses, 63% of chronic aggressive hepatitis, 50% of HBsAg-positive liver carcinoma, but only 17% of chronic persistent hepatitis or 7% of healthy blood donors were anti-HBc IgM-positive. Determination of anti-HBc IgM is useful in detecting atypical hepatitis B virus infections without HBsAg in serum and, with some restrictions, in discriminating acute and chronic hepatitis type B.

A new serologic marker in ankylosing spondylitis

Sera of patients with ankylosing spondylitis (AS) were screened for the presence of antibodies by indirect immunofluorescence staining of polytene chromosomes of Drosophila melanogaster. Thirty-nine percent of the sera tested contained antibodies which selectively reacted with an antigen(s) present at the chromosomal locus 93D after heat shock treatment. This indicates a novel antibody specificity in a subgroup of AS patients and may provide a new aid in the diagnosis of AS.

Hepatitis B virus transcription in the infected liver

Hepatitis B virus (HBV) transcription was studied in the liver of an infected chimpanzee and compared with HBV transcription in heterologous systems. Besides the well characterized 2.3-kb surface antigen mRNA produced in most systems, a second major transcript was identified in the liver. This 3.8-kb transcript (+/- 300 bases) is slightly larger than the HBV genome and is probably involved both in core/e antigen synthesis and in HBV replication via reverse transcription. In addition, minor variants of the 2.3-kb surface antigen mRNA were characterized as probably being involved in the expression of HBsAg-related minor proteins. Finally, several potential transcription signals, identified on the HBV genome using heterologous expression systems, were found to be poorly active if at all in the infected liver, thereby stressing the importance of HBV transcription studies performed with liver material.

Detection of hepatitis B viral DNA in sera positive for antibody to delta antigen

Hepatitis B virus (HBV) DNA was detected in 17 sera positive for antibody to delta antigen (anti-delta). Six sera from two patients were positive for HBV DNA. Analysis by the Southern blot technique showed identity between HBV DNA in anti-delta-positive and anti-delta-negative sera. These results show that anti-delta-positive sera contain HBV DNA, although these sera were also positive for antibodies to hepatitis B e antigen.

Expression of hepatitis B antigens with a simian virus 40 vector

Recombinant DNA molecules consisting of the simian virus 40 (SV40) early region and different subgenomic hepatitis B virus DNA fragments were constructed in vitro and packaged in vivo into SV40 capsids by using a complementing SV40 helper virus. Upon infection with these virus stocks the three known hepatitis B-specific antigens were expressed under SV40 control. The surface antigen was released into the medium, and the core antigen and its derivative hepatitis B e antigen were only detected intracellularly. Size analysis of the core gene product(s) by immunoblotting revealed the presence of a single protein species identical with the 21-kilodalton core antigen isolated from human liver. The hepatitis B core antigen expressing construct did not contain a putative precore sequence, indicating that such a sequence is not needed for hepatitis B core antigen synthesis in animal cells. S1 analysis demonstrated the use of SV40 signals for initiation and polyadenylation of the core gene transcripts. In addition, a processing-polyadenylation signal was identified within the core gene.

HBV-DNA in sera of patients with HBsAg-positive primary liver cell carcinoma

Sera of ten patients with HBsAg-positive primary liver carcinoma were tested for anti-HBc-IgM and HBV-DNA. Five patients were positive for anti-HBc-IgM and six for HBV-DNA. There was no correlation between the presence of anti-HBc-IgM and HBV-DNA. Our study suggests that complete viral replication exists in some HBsAg-positive primary liver carcinomas.

Characterization of endogenous phosphorylation in isolated cardiac sarcolemma

The cardiac sarcolemma contains kinases which catalyze the incorporation of 32P-phosphate into acid stable and acid precipitable membrane components of low molecular weight. The phosphorylation is not influenced by cyclic AMP or calmodulin. Analysis of phosphorylation products using proteolytic digestion, organic solvent extraction, thin layer chromatography and gel filtration reveals both polypeptides and lipids as kinase substrates. Polypeptides are phosphorylated at their serine and threonine residues, while lipid phosphorylation gives rise to 32P-labelled phosphatidylinositol phosphates and some nonidentified compounds. Phosphorylated polypeptides and phosphorylated lipids do not separate in SDS polyacrylamide gel electrophoresis. On the basis of the fast time course of 32P-phosphate incorporation, it may be supposed that endogenous phosphorylation may play a role in the short term regulation of the cardiac sarcolemmal function.

Signals regulating hepatitis B surface antigen transcription

About 200 million people are chronic carriers of hepatitis B surface antigen (HBsAg), but since hepatitis B virus (HBV) cannot be propagated in vitro, HBsAg transcription has been studied only in cell lines containing HBV DNA integrated into chromosomes, and HBsAg-related mRNAs 2.0 to 2.5 kilobases (kb) long have been described. We have analysed the transcripts produced in an infected chimpanzee liver and in a rat cell line containing HBV DNA. In contrast to previous suppositions we report here that the major S gene transcript initiates close to the S gene, that is, within the 'pre-S' region and is processed/polyadenylated at a site situated within the core gene. The efficiency of processing/polyadenylation at this site varies between the chimpanzee liver and the rat cell line studied. The S gene promoter does not contain a TATA box but instead has a sequence homologous to that which positions the 5' ends of the major simian virus 40 (SV40) late transcript.