Determination of protein spots separated by two-dimensional polyacrylamide gel electrophoresis

Albumin mRNA expression in human liver diseases and its correlation to serum albumin concentration

The expression of albumin mRNA in human liver samples was investigated in order to understand the molecular mechanism of albumin gene expression in various liver diseases. Albumin mRNA in acute hepatic failure and decompensated liver cirrhosis was reduced significantly compared to normal control liver (P less than 0.05). Serum albumin concentration is closely correlated with albumin mRNA content (r = 0.895, P less than 0.01). These data suggest that albumin concentration is mainly regulated at albumin mRNA level in the liver despite the presence of other regulatory mechanisms and that expression of albumin mRNA level is correlated with disease severity. But in several cases there was a discrepancy between albumin mRNA level and severity of liver disease, so further investigation of the regulatory factors of albumin gene expression should be performed.

Transcriptional regulation of an aldolase gene in the regenerating rat liver

The relative abundance of rat aldolase A, B, C, alpha-fetoprotein, and albumin mRNAs was determined by Northern hybridization during liver regeneration after partial hepatectomy. Aldolase A mRNA increased more than 10-fold on the 3rd day after partial resection compared with that of normal adult rat liver. S1 analysis revealed that three species of aldolase A mRNAs (mRNA I, II & III) reappeared. However, transcriptional rate of aldolase A mRNA did not change at all during the regeneration. In contrast, aldolase B, aldolase C and albumin mRNAs did not change at all. These findings suggest that the differentiated hepatocyte maintains a differentiated state during the liver regeneration as seen in aldolase B, whereas "oncofetal" isozymes such as aldolase A resurge after partial hepatectomy under the control of post-transcriptional mechanism.

Construction and expression of human aldolase A and B expression plasmids in Escherichia coli host

E. coli expression plasmids for human aldolases A and B (EC 4.1.2.13) have been constructed from the pIN-III expression vector and their cDNAs, and expressed in E. coli strain JM83. Enzymatically active forms of human aldolase have been generated in the cells when transfected with either pHAA47, a human aldolase A expression plasmid, or pHAB 141, a human aldolase B expression plasmid. These enzymes are indistinguishable from authentic enzymes with respect to molecular size, amino acid sequences at the NH2- and COOH-terminal regions, the Km for substrate, fructose 1,6-bisphosphate and the activity ratio of fructose 1,6-bisphosphate/fructose 1-phosphate (FDP/F1P), although net electric charge and the Km for FDP of synthetic aldolase B differed from those for a previously reported human liver aldolase B. In addition, both the expressed aldolases A and B complement the temperature-sensitive phenotype of the aldolase mutant of E. coli h8. These data argue that the expressed aldolases are structurally and functionally similar to the authentic human aldolases, and would provide a system for analysis of the structure-function relationship of human aldolases A and B.

RNA processing by RNase III is involved in the synthesis of Escherichia coli polynucleotide phosphorylase

The synthesis of Escherichia coli polynucleotide phosphorylase (PNPase) was examined in a mutant strain defective in the RNA processing enzyme RNase III (Rnc-). We found that the specific activity and the synthesis rate of PNPase were increased in the Rnc- strain by more than three times that in an Rnc+ strain. Such increased synthesis of PNPase was not observed in a mutant strain transformed with a plasmid carrying the rnc+ gene. Quantitative analysis of RNA showed that the transcripts from the pnp gene, which encodes PNPase, were degraded more slowly in the Rnc- strain than in the Rnc+ strain. These results indicate that processing of the transcripts by RNase III is intimately involved in controlling the expression of pnp by affecting the stability of its messenger RNA.

An antigen expressed in proliferating cells at late G1-S phase

A monoclonal antibody Pr-28 was prepared, which recognized an antigen present only in proliferating cells. Immunofluorescence analysis of Pr-28 antigen showed that the antigen was localized mainly in perinuclear cytoplasm. Although Pr-28 antibody was produced against a chicken cell antigen, it reacts not only with chicken cells but also other cells of murine origin, such as L-cells and NIH 3T3 cells. The molecular weight (Mr) of the antigen recognized by Pr-28 antibody was 45,000 D as determined by SDS-PAGE run under reducing conditions. The antigen disappeared in NIH 3T3 quiescent cells, reappearing in quiescent cells stimulated by fetal calf serum (FCS). The synthesis of Mr 45,000 protein occurred at late G1 phase, just before DNA synthesis in serum-stimulated quiescent NIH 3T3 cells and ceased in S phase.

Inhibition of neutrophil superoxide formation by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), and inhibitor of protein kinase-C

Superoxide formation of human neutrophils stimulated by phorbol 12-myristate 13-acetate (PMA), N-formyl-methionyl-leucyl-phenylalanine, or calcium ionophore A23187 was inhibited by pretreatment of the cells with 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), an inhibitor of protein kinase-C, but was not inhibited by N-(2-guanidinoethyl)-5-isoquinolinesulfonamide which has a less inhibitory effect on the protein kinase-C. H-7 also inhibited superoxide formation of PMA-activated cytoplasts, which lack nuclei and granules. The phosphorylation of proteins induced by PMA in the cytoplasts as well as the intact neutrophils was also inhibited by preincubation with H-7. Among several phosphoproteins affected by H-7, one protein with a molecular weight of 19,000 (pI = 4.9) was inhibited markedly. N-(2-Guanidinoethyl)-5-isoquinolinesulfonamide did not inhibit the phosphorylation of proteins induced by PMA. These findings support the possibility that the protein kinase-C is involved in the activation process of superoxide formation.

Expression of three mRNA species from a single rat aldolase A gene, differing in their 5' non-coding regions

The complete nucleotide sequence of the rat aldolase A isozyme gene, including the 5' and 3' flanking sequences, was determined. The gene comprises ten exons, spans 4827 base-pairs and occurs in a single copy per haploid rat genome. The genomic DNA sequence was compared with those of three species of rat aldolase A mRNA (mRNAs I, II and III) that have been found to differ from each other only in the 5' non-coding region and to be expressed tissue-specifically. It revealed that the first exon (exon M1) encodes the 5' non-coding sequence of mRNA I, while the second exon (exon AH1) encodes those of mRNAs II and III and the following eight exons (exons 2 to 9) are shared commonly by all the mRNA species. These results allowed us to conclude that mRNA I and mRNAs II, III were generated from a single aldolase A gene by alternative usage of exon M1 or exon AH1 in addition to exons 2 to 9. S1 nuclease mapping of the 5' ends of their precursor RNAs suggested that these three mRNA species were transcribed from three different initiation sites on the single gene.

Human aldolase isozyme gene: the structure of multispecies aldolase B mRNAs

A complete nucleotide sequence of human aldolase B mRNA was determined with a recombinant cDNA (pHABL120-3). The cDNA insert was composed of 1,652 bases excluding poly(A) tail and the sequence was consistent with the previous results reported by others. However, S1 nuclease mapping and subsequent genomic analysis allowed us to know that the clone possesses two more sites corresponding to 5'-termini in the 5'-noncoding region and another site of polyadenylation in the 3'-noncoding region. In fact, the major aldolase B mRNA species occupying 90% of the total mRNAs initiated at the predominant position corresponding to the position around -82 of the 5'-noncoding sequence in pHABL120-3 and terminated at the distal polyadenylation site. Second species accounting for 9% of the mRNAs initiated at the same site and terminated at the proximal polyadenylation site. The remainings have a longer 5'-noncoding sequence which starts from further upstream region of the major one and pHABL120-3 corresponds to one of these largest clones.