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Biomedical subjects

M J Chu

Publications and source records attributed to M J Chu.

8 recordsLinked to original sources
PubMed1998

Cytotoxic sterols from the soft coral Nephthea erecta.

Two new cytotoxic sterols, 24-methylcholesta-5,24(28)-diene-3beta, 15beta,19-triol (1) and 24-methylcholesta-5,24(28)-diene-3beta, 19-diol-7-one (2), as well as four cytotoxic sterols, 24-methylcholesta-5,24(28)-diene-3beta,19-diol (3), 24-methylcholesta-5,24(28)-diene-3beta,19-diol-7beta-mono aetate (4), 24-methylcholesta-5,24(28)-diene-3beta,7beta,19-triol (5), and 24-methylcholesta-24(28)-ene-3beta,5alpha,6beta,19-tet raol (6), have been isolated from the soft coral Nephthea erecta. The structures of compounds 1 and 2 were determined by spectral analysis.

Animals↗
PubMed1996

Transcription of the human hepatic lipase gene is modulated by multiple negative elements in HepG2 cells.

The expression of the hepatic lipase (HL) gene is highly tissue specific. In order to identify cis-acting elements which regulate the expression of this gene in the liver, multiple deletion mutants of the 5'-flanking region of the HL gene fused to the human growth hormone gene were transfected in HepG2 cells, which normally produce HL. Transient expression assays indicated the presence of negative (at nucleotides (nt) -1576(/)-1342 and -623(/)-407) and positive (at nt -1862(/)-1576 and -50(/)-9) regulatory elements. Transfection of HeLa cells, which do not produce HL, with the same deletion constructs resulted in a similar pattern of promoter activities. However, additional negative (nt -138/-50) and positive (nt -407(/)-138) elements were found. DNase I footprint analysis of the proximal and distal HLpromoter sequences with HepG2 and HeLa cell nuclear extracts identified seven protected regions: A, nt -1540(/)-1527; B, -1505(/)-1473; C, -1467(/)-1460; D, -592(/)-577; E, -565(/)-545; F, -234(/)-220; and G, -70(/) -48. Sites A, B, C, D and E were located within regions containing negative regulatory elements. In order to determine which nuclear factor interacts with the negative elements, sites B, D and E were mutated and the effects of mutation on competition in a gel retardation assay and on promoter activity were studied. When the binding motif for AP1 in sites B, D and E was mutated, the specific DNA-protein complexes were not competed with the mutant oligonucleotides and promoter activity increased twofold. The magnitude of the increase is less than expected from the deletion analysis, and simultaneous mutations did not cause further increase in promoter activity, which suggests that other sites are involved in this negative modulation. These results suggest that the transcription of the HLgene in HepG2 cells is negatively modulated by multiple cis-acting negative elements and AP1-like nuclear factor may play some role in this modulation.

Base Sequence↗
PubMed1995

Partial structure of the mouse glucokinase gene.

A complementary DNA for glucokinase (GK) was cloned from mouse liver total RNA by a combination of the polymerase chain reaction (PCR) and mouse liver cDNA library screening. Liver- and beta-cell-specific exons 1 were isolated by PCR using mouse and rat genomic DNAs. These clones were then used to screen a mouse genomic library; three genomic clones were isolated and characterized. The mouse GK gene spans over 20 kb, containing 11 exons including a liver- or beta-cell-specific exon 1, which encodes a tissue-specific 15-aa peptide at the N-terminus of the protein. Both types of GK contain 465 amino acid residues. The predicted amino acid sequence of mouse beta-cell-specific GK showed 98 and 96% identity to the rat and human enzymes, respectively; the corresponding values are 98 and 95%, respectively, for the liver-specific GK. Several transcription factor-binding consensus sequences are identified in the 5' flanking region of the mouse GK gene.

Amino Acid Sequence↗
PubMed1994

Mouse very-low-density-lipoprotein receptor (VLDLR) cDNA cloning, tissue-specific expression and evolutionary relationship with the low-density-lipoprotein receptor.

The very-low-density-lipoprotein receptor (VLDLR) is a recently described lipoprotein receptor that shows considerable similarity to the low-density-lipoprotein receptor (LDLR). This receptor has been suggested to be important for the metabolism of apoprotein-E-containing triacylglycerol-rich lipoproteins, such as very-low-density-lipoprotein (VLDL), beta-migrating VLDL and intermediate-density lipoprotein. cDNA clones that code for the VLDLR were isolated from a mouse heart cDNA library. The deduced amino acid sequence predicts a mature protein of 846 amino acids preceded by a 27-residue signal peptide. Three mRNA species for the VLDLR with sizes of 3.9, 4.5 and 7.9 kilobases were present in high concentration in heart and muscle, which utilize triacylglycerols as an energy source. VLDLR mRNA is also detected in decreasing amounts in kidney, brain, ovary, testis, lung and adipose tissue. It is essentially absent in liver and small intestine. The amino acid sequence of the VLDLR is highly conserved among rabbit, human and mouse. VLDLR contains five structural domains very similar to those in LDLR, except that the ligand-binding domain in VLDLR has an eightfold repeat instead of a sevenfold repeat in LDLR. Sequence conservation among animal species is much higher for the VLDLR than the LDLR. Sequences of the VLDLR from three vertebrate species and the LDLR from five vertebrate species were aligned and a phylogenetic tree was reconstructed. Although both receptors contain five domains and share amino acid sequence similarity, our computations showed that they diverged before the divergence between mammals and amphibians. In addition, sequence comparison of both receptor sequences suggests that the rabbit is evolutionarily closer to man than to the mouse. These results are consistent with the hypothesis that the VLDLR and the LDLR have evolved from a common ancestral gene to play distinct roles in lipoprotein metabolism and that the metabolic handling of triacylglycerol by the body via the VLDLR is a highly conserved mechanism.

Amino Acid Sequence↗
PubMed1987

The complete nucleotide sequence of the cloned DNA of hepatitis B virus subtype adr in pADR-1.

The complete nucleotide sequence of the cloned hepatitis B virus DNA subtype adr in pADR-1 was determined by Maxam and Gilbert's method. It is 3215 base pairs in size, which is 27 bp longer than the sequence of the adr pHBr330, as reported by Ono et al. The nucleotide difference between pADR-1 and adr pHBr330 is about 2% while those between pADR-1 and adw as well as ayw are 9.3% and 9.7% respectively. In this paper, the heterogeneity and homogeneity of the S gene, the C gene and the other coding regions in pADR-1 and in the other subtypes are compared and discussed.

Base Sequence↗
PubMed1984

The nucleotide sequence of surface antigen gene of hepatitis B virus subtype adr.

The nucleotide sequence of the XhoI-BamHI fragment (1279bp), which contains the surface antigen gene (S gene) of HBVadr, was determined by Maxam and Gilbert's method. By comparing the differences both of the nucleotide sequence in the S gene and its coded amino acid sequence between adr and those reported for adw, ayw and adyw, some new variation sites were discovered. The differences were mainly distributed in the two hydrophilic regions. However, at those sites which might show biological function, there were no variations among different subtypes, they are relatively conservative in heredity and evolution. Comparing the variation of the nucleotide sequence in the S gene region with that in the non-S gene region, it is shown that the frequency of variation in the non-S gene region doubled that in the S gene region. The S gene region is more conservative.

Amino Acid Sequence↗