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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.

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.

Osteoclastogenesis inhibitory factor (OCIF) is a heparin-binding secretory glycoprotein that belongs to the tumor necrosis factor receptor (TNFR) family. OCIF is present both as a approximately 60-kDa monomer and a disulfide-linked homodimer. We attempted to characterize the seven structural domains of OCIF by determining the capabilities of various OCIF mutants to inhibit osteoclastogenesis, to interact with heparin, and to form dimers. We also examined a potential of domains 5 and 6, death domain homologous regions (DDHs), for inducing cell death by expressing OCIF/Fas fusion proteins. Our results show that: (i) the N-terminal portion of OCIF containing domains 1-4, which have structural similarity to the extracellular domains of the TNFR family proteins, is sufficient to inhibit osteoclastogenesis; (ii) a heparin-binding site is located in domain 7, and affinity for heparin does not correlate with the inhibitory activity; (iii) Cys-400 in domain 7 is the residue responsible for dimer formation; and (iv) the C-terminal portion containing domains 5 and 6, DDHs, has a high potential for mediating a cytotoxic signal when it is expressed in cells as an OCIF/Fas fusion protein in which the transmembrane region of Fas is inserted in front of DDHs.

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.

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.