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DNase I footprinting and gel mobility shift analysis showed that an HuH-7 hepatoma nuclear protein, termed AFP1, binds specifically to an AT-rich sequence, TGATTAATAATTACA, in domain B of the human alpha-fetoprotein enhancer. No such binding activity was found in HeLa cell nuclei. Transient transfection studies showed that a 54-base-pair region corresponding to the AFP1-binding site could stimulate the simian virus 40 early promoter to express a linked chloramphenicol acetyltransferase gene in an orientation-independent and cell-specific manner. The correlation between the binding of AFP1 and the stimulation of chloramphenicol acetyltransferase gene expression strongly suggests that specific interaction of AFP1 with the AT motif is important for cell-specific transcriptional enhancement. Competition gel mobility shift analysis revealed that similar AT-rich sequences with high affinities to AFP1 were also present in the promoters of the alpha-fetoprotein and albumin genes. These results suggest that AFP1 may function as a common regulatory factor in the transcription of the alpha-fetoprotein and albumin genes.

Ley determinant (Fuc alpha 1----2Gal beta 1----4[Fuc alpha 1----3]GlcNAc beta 1----R) defined by mAb BM-1 is highly expressed in human immunodeficiency virus (HIV)-infected T cell lines and in CD3+ peripheral mature T cells of patients with acquired immune deficiency syndrome (AIDS) or with AIDS-related complex (ARC). Ley expression increased greatly in the CD3+ population in the advanced stage of AIDS when the CD4+ population decreased greatly. Six other carbohydrate antigens tested by their respective mAbs were not detected in these same cells. None of the carbohydrate antigens tested by the seven mAbs used in this study were found in noninfected T cell lines and in normal peripheral blood lymphocytes.

UCN-01 is a staurosporine-related compound that was isolated from the culture broth of Streptomyces sp. and shows potent and selective inhibitory activity against protein kinase C. Cellular inhibitory activity of UCN-01 against protein kinase C and cytotoxicity of UCN-01 were compared with those of staurosporine. When the mechanism of inhibitory activity was investigated in vitro, UCN-01 as well as staurosporine inhibited the activity of the catalytic domain of protein kinase C. In spite of direct inhibition against the catalytic domain of protein kinase C, cytotoxicity of UCN-01 was much lower than that of staurosporine. In addition, UCN-01 showed more selective inhibitory activity against protein kinase C than did staurosporine because of the sole structural difference at C-7. Therefore, a series of 7-O-alkyl derivatives of UCN-01 was synthesized and investigated. Interestingly, one of the compounds, the beta-methoxy derivative, showed 3-fold greater potency and 17-fold more selective inhibitory activity against protein kinase C than did UCN-01.

DNA complementary to human alpha-fetoprotein (AFP)mRNA was cloned in the plasmid pBR322. Analysis of three overlapping cDNA clones revealed most of the nucleotide sequence of AFP mRNA, and the remaining nucleotides at the 5' end of the mRNA were elucidated from a cloned genomic DNA fragment. The amino acid sequence was deduced from the nucleotide sequence, which revealed 19 amino acids in the signal sequence and 590 amino acids in mature AFP. There are 15 regularly spaced disulfide bridges, which generate a folding structure having three repeating domains. There is one potential N-glycosylation site, Asn-Phe-Thr, in the amino acid sequence. In comparison with mouse AFP, 66% of the amino acid sequence was conserved, with the highest identity (72%) in domain 3, followed by domain 2 (67%) and domain 1 (59%). In comparison with human albumin, a 39% conservation of primary structure was found. Again, the similarity was the highest in domain 3 and the lowest in domain 1. Human AFP and human albumin are similar in overall structure, but certain parts of the molecules differ significantly in their predicted secondary structure.

The human alpha-fetoprotein (AFP) gene was isolated into three overlapping clones in bacteriophage lambda vectors and its sequence organization analyzed by restriction endonuclease mapping and nucleotide sequencing. The human AFP gene is about 20 kilobase pairs long and contains 15 exons and 14 introns. The overall organization of the human AFP gene is similar to that of the mouse AFP gene, with all but two exons showing identical sizes. Nucleotide sequences at all exon/intron junctions display similarity to the consensus boundary sequence (Breathnach, R., and Chambon, P. (1981) Annu. Rev. Biochem. 50, 349-383), with the GT-AG rule applied to the splicing point. The cap site maps 44 nucleotides upstream from the translation initiation site. The "TATA box" is located 27 nucleotides upstream from the putative cap site and is flanked by sequences with dyad symmetry. The TATA box can thus be placed in the loop portion of a possible stem-loop structure formed by intrastrand base-pairing. Other characteristic nucleotide sequences in the 5' flanking region include a CCAAC pentamer, a 14-base pair (bp) enhancer-like sequence, and a 9-bp sequence homologous to the glucocorticoid responsive element. A long (90 bp) direct repeat and several alternating purine/pyrimidine sequences are also present in the 5' flanking region. A 736-bp sequence of the 5' flanking region adjacent to the cap site of the human AFP gene shows a 61% similarity with the corresponding region of the mouse AFP gene. There are two Alu family sequences and two poly(dT-dG) repeats in the human AFP gene that show different distribution patterns from those in the mouse AFP gene.

Summary.The synthesis of alpha1-fetoprotein (AFP) was measured by radioimmunoassay in tissues and fluids of 19 bovine embryos (14–46 days of gestation) and in tissue cultures of 4 pre-implantation embryos (17–27 days) by incorporation of radioactive methionine. AFP was first detected in Day-14 trophoblasts and secretion of AFP into allantoic fluid occurred by Day 16. Embryonic tissues and fluids in pre-implantation and post-implantation embryos contained levels of AFP that were 550 to 1 500 000 times higher than those found in maternal serum (3·9–298 000 compared with 0·07–0·25 ng/mg protein). High levels of AFP were also found in uterine fluid which suggested significant transfer of this protein from the early post-implantation conceptus. The major sites of AFP synthesis were yolk sac and fetal liver. It is concluded that the synthesis of bovine AFP is not initiated by events associated with implantation.

Expression of the mouse alpha-fetoprotein gene in embryonic, adult, and neoplastic tissues was assessed by RNA dot hybridization using 32P-labeled alpha-fetoprotein cDNA as probe, alpha-fetoprotein mRNA was present in high levels in total RNA from yolk sac endoderm, fetal liver, and an alpha-fetoprotein-producing hepatoma. In contrast, this mRNA was greatly depleted in total RNA from yolk sac mesoderm and essentially absent in brain, adult liver, and a non-alpha-fetoprotein-producing hepatoma. These results indicated that alpha-fetoprotein gene expression was controlled primarily at the transcriptional level. The presence of the modified base, 5-methylcytosine, in the alpha-fetoprotein gene was studied by comparing hybridization patterns obtained by Southern blot analysis of DNA cleaved with the restriction endonuclease isoschizomers Msp I and Hpa II. The gross sequence organization and reiteration frequency of the alpha-fetoprotein gene were invariant among the DNA samples, whereas, in each case, there was a positive correlation between hypomethylation of six CCGG (Hpa II) sites in the alpha-fetoprotein gene and expression of this gene. These Hpa II sites were distributed throughout a large portion of the alp]a-fetoprotein gene. Patterns of cytosine methylation in this gene were established before day 15 of gestation in yolk sac endoderm and mesoderm.

Using a titration procedure, we measured the proportion of alpha-fetoprotein (AFP) and albumin mRNA in normal, regenerating, and preneoplastic rat livers. AFP mRNA constitutes approximately 0.006% of the polysomal polyadenylated RNA of normal livers and this proportion increases only slightly before the onset of DNA synthesis in liver regeneration induced by partial hepatectomy or CCl4 injury. In either model of liver regeneration, the proportion of AFP mRNA in polysomal RNA is highest approximately 24 h after the peak of DNA synthesis. The increase in the proportion of AFP mRNA in polysomal RNA is relatively small during liver regeneration (2-4-fold) but is larger (30-50-fold) in preneoplastic livers of rats fed a choline-deficient diet containing 0.1% ethionine. In contrast to those changes in AFP mRNA, albumin mRNA levels remain unchanged during liver regeneration and double in preneoplastic livers. Our results indicate that the concept of "retrodifferentiation" as it applies to liver regeneration and certain types of hepatic neoplasia needs reevaluation.

We describe experiments showing that the 5′-flanking region of the human alpha-fetoprotein (AFP) gene contains transcription control elements with characteristics of enhancers. The enhancer activity was detected and characterized by the ability to direct the expression of a linked chloramphenicol acetyltransferase (CAT) gene in transfected AFP-producing hepatoma cells in culture. The enhancer activity is cell-specific in that it occurs in hepatoma cells producing AFP, but not in non-AFP-producing hepatoma or nonhepatic cells. The active elements can direct CAT expression in conjunction with the SV40 promoter in an orientation- and position-independent manner. The sequences important for enhancer activity reside in the 400-base pair region between 3.3 and 3.7 kilobase pairs upstream of the AFP gene. This and proximal upstream regions contain multiple enhancer “core”-like sequences and other stretches of potential biological significance.

Secretion and glycosylation of alpha-foetoprotein (AFP) by mouse yolk sac were studied by using yolk-sac explants cultured in vitro. Yolk-sac explants rapidly incorporated [35S]methionine into AFP, whereas radioactively labelled AFP was not found in the medium until 30 min after incubation was initiated. Electrophoretic analysis revealed that microheterogeneity of AFP synthesized in explants increased in parallel with the gestational age of the yolk sacs. The change in microheterogeneity was noted by the formation of increasingly acidic forms. Only the most acidic forms of AFP were found to be present in the medium on each gestational day studied. Tunicamycin reduced the incorporation of glucosamine into AFP with a concomitant decrease in molecular weight and microheterogeneity. However, the relative amount of AFP released into the medium was not altered by the presence of tunicamycin. The presence of under-glycosylated AFP in the medium indicates that glycosylation of AFP is not essential for its secretion from the yolk sac. In light of these and previous findings, it is suggested that the glycosylation of AFP may be important for the turnover of this glycoprotein in serum.

The human ATBF1 cDNA reported previously, now termed ATBF1-B, encodes a 306-kDa protein containing 4 homeodomains and 18 zinc fingers including one pseudo zinc finger motif. Here, we report the isolation of a second ATBF1 cDNA, 12 kilobase pairs long, termed ATBF1-A. The deduced ATBF1-A protein is 404 kDa in size and differs from ATBF1-B by a 920-amino acid extention at the N terminus. Analysis of 5'-genomic sequences showed that the 5'-noncoding sequences specific to ATBF1-A and ATBF1-B transcripts were contained in distinct exons that could splice to a downstream exon common to the ATBF1-A and ATBF1-B mRNAs. The expression of ATBF1-A transcripts increased to high levels when P19 and NT2/D1 cells were treated with retinoic acid to induce neuronal differentiation. Preferential expression of ATBF1-A transcripts was also observed in developing mouse brain. Transient transfection assays showed that the 5.5-kilobase pair sequence upstream of the ATBF1-A-specific exon (exon 2) supported expression of the linked chloramphenicol acetyltransferase gene in neuronal cells derived from P19 cells but not in undifferentiated P19 or in F9 cells, which do not differentiate into neurons. These results showed that ATBF1-A and ATBF1-B transcripts are generated by alternative promoter usage combined with alternative splicing and that the ATBF1-A-specific promoter is activated during neuronal differentiation.

We have characterized the 5' and 3' regions of the human albumin gene with respect to nucleotide sequences, mRNA transcription initiation and polyadenylation. There are at least two transcription initiation sites and two polyadenylation sites in the human albumin gene. The multiple transcription initiation sites are utilized almost equally. The two polyadenylation sites are used differentially, with the site proximal to the protein termination codon dominating. The “TATA” and the “CCAAT” boxes are present at about 30 and 90 nucleotides upstream of the putative cap sites. About 250 nucleotides immediately 5' to the transcription initiation sites are highly conserved among the human, rat, and chicken. Within the 1-kilobase pair 5' flanking region of the human albumin gene there are 8- and 35-base pair alternating purine/pyrimidine sequences, primarily consisting of dG and dT, and three nucleotide segments exhibiting homology to the proposed progesterone receptor-binding site. In these and other characteristics, the 5' flanking region of the human albumin gene is distinct from the corresponding region of the human alpha-fetoprotein gene. Each of the two polyadenylation sites of the human albumin gene is preceded by a AATAAA hexamer. In addition, the first polyadenylation site has several conserved sequences believed to play a role in the 3'-end formation. The second polyadenylation site lacks these signals which may explain why it is used less frequently. In spite of these differences the two polyadenylation sites show a high overall sequence similarity, suggesting that they arose by duplication. There is no major difference between the normal liver and hepatoma cells in the relative utilization of multiple sites for transcriptional initiation and polyadenylation of the human albumin gene, suggesting that the albumin mRNA polymorphism has no direct relevance to hepatocarcinogenesis.

cDNA clones coding for a T-cell receptor beta-chain were isolated from a beef insulin/IAd-reactive T-cell hybridoma, A20.2.15, and its complete amino acid sequence was deduced. This beta-chain gene utilizes the same V beta segment as a thymocyte beta-chain gene (86T1) and rearranges to the 5' proximal J-C locus (J beta 1-C beta 1), thus providing definitive evidence of a beta-chain gene from a functional hybridoma that utilizes C beta 1. The amino acid sequence of the V beta gene in A20.2.15 is identical to 86T1, thus suggesting the absence of somatic mutation in the beta-chain of A20.2.15. Southern blot analysis revealed a somatic DNA rearrangement unique to the A20.2.15 hybridoma. The expression of this gene in the hybridoma was confirmed by RNA dot hybridization. All 24 beta-chain clones so far isolated from the A20.2.15 hybridoma contained C beta 1, suggesting that the beta-chain gene of the fusion partner BW5147 is not expressed in the hybridoma.

A Schizosaccharomyces pombe gene encoding adenylate cyclase has been cloned by cross-hybridization with the Saccharomyces cerevisiae adenylate cyclase gene. The protein encoded consists of 1692 amino acids and has adenylate cyclase activity that cannot be activated by the Sa. cerevisiae RAS2 protein. Sc. pombe cyclase has a high degree of homology (approximately 60%) with the catalytic domain of Sa. cerevisiae cyclase precisely mapped by a gene-deletion analysis. A 25-40% identity is observed throughout the middle segments of approximately 1000 residues of both cyclases, large parts of which are composed of repetitions of a 23-amino acid motif similar to those found in human glycoproteins, Drosophila chaoptin, and Toll gene product. However, a segment corresponding to the NH2-terminal 620 residues of Sa. cerevisiae cyclase appears lost from Sc. pombe cyclase, and the COOH-terminal 140 residues are not well conserved between the two yeast species. Deletions involving the COOH-terminal residues of Sa. cerevisiae cyclase cause loss of activation by the RAS2 protein. These results suggest that Sc. pombe cyclase may have lost the ability to interact with RAS proteins by the loss of a regulatory site.

The level of α-fetoprotein (AFP) mRNA in HuH-7 human hepatoma cells is elevated by the addition of dexamethasone to the culture medium. To locate the DNA region involved in hormonal regulation of the AFP gene, we constructed recombinant plasmids in which various lengths of the 5′-flanking sequence of the human AFP gene were fused to the CAT gene. Various cell lines were transfected with the recombinant plasmids, incubated with or without 3 × 10−6Mdexamethasone, and then assayed for chloramphenicol acetyltransferase expression. In hepatoma cells that produce AFP, the dexamethasone treatment resulted in the stimulated chloramphenicol acetyltransferase expression when the transfected plasmids contained 169 base pairs (bp) or longer AFP 5′-flanking sequence. No dexamethasone effect was observed when the 5′-flanking sequence was less than 98 bp long. The dexamethasone stimulation was effectively suppressed by the glucocorticoid antagonist RU486, indicating that this effect is mediated by glucocorticoid receptors. The 71-bp region between positions −169 and −98 contains a nucleotide stretch which is similar to the consensus sequence of the glucocorticoid responsive element (GRE). Partial alterations of this sequence resulted in decreased dexamethasone response. The GRE-containing region stimulated heterologous (SV40) promoter activity in response to dexamethasone treatment in an orientation- and position-independent manner. The GRE and the upstream AFP enhancer function independently from each other.