Primary structures of human alpha-fetoprotein and its mRNA.

Abstract

DNA complementary to human a-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 ofprimary 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. a-Fetoprotein (AFP) is a major serum protein (Mr, =70,000) synthesized during fetal life (1-4). Reappearance of AFP in adult serum often signals pathological conditions, particularly hepatocarcinomas and teratocarcinomas (1-4). In contrast, albumin increases steadily during fetal and neonatal growth and shows no apparent changes in concentration associated with development of liver and germ cell tumors.In the past several years, DNAs complementary to mouse (5, 6) and rat (7) AFP mRNAs and rat (8) and human (9, 10) albumin mRNAs have been cloned. Nucleotide sequences of these clones and the amino acid sequences deduced from them have provided valuable information on the structure of these proteins. However, the rat cDNA clones are not full-length and consequently, molecular comparisons have been limited to partial sequences of mouse and rat AFPs. Also, comparisons between AFP and albumin were possible only interspecially because neither mouse albumin nor human AFP mRNA sequences were known in their entirety.In this paper we report the complete nucleotide sequence of human AFP mRNA and the amino acid sequence of AFP. These data allow comparisons of the entire primary structures of AFPs interspecially and AFP and albumin intraspecially. MATERIALS AND METHODSThe production of the cDNA clone, pHAF2, containing 841 nucleotides or about 40% of the human AFP mRNA sequence at the 3' end was described (11). By using the nick-translated insert of pHAF2 as a probe, a second clone, pHAF6, with an additional 320 nucleotides at the 5' end was obtained (Fig. 1).

Immunohistologic study on the expressions of α-fetoprotein and protein induced by vitamin K absence or antagonist II in surgically resected small hepatocellular carcinoma

“…9,21 Possible factors or mechanisms of PIVKA-II increase in the serum of HCC patients are: 1) qualitative or quantitative abnormality of prothrombin precursors; 2) changed activity of ␥-glutamyl carboxylase, i.e., the key enzyme of ␥-carboxylation; 3) lack of vitamin K; and 4) abnormality in the vitamin K cycle. 12 PIVKA-II expression in HCC tissues was confirmed by Nohno, 22 Tamano, 23 and Nakagawa et al, 24 but its expression in small HCC has not yet been studied in depth.…”

“…5,12 In the fetus, AFP is produced by the yolk sac and liver. In adults, it is well known that AFP is produced in HCC.…”

Detection of alpha-foetoprotein messenger RNA in human hepatocellular carcinoma and hepatoblastoma tissue

“…Where AFP mRNA migrated as a discrete band, it was in the region of 20S RNA species (Figure 2). This is in keeping with the size of human AFP transcripts deduced from AFP cDNAs of a human testicular cell line (Morinaga et al, 1983), but has not been shown previously in human HCC. In the other 3 human tumours positive by Northern blot (Figure 2) was generally localized in cells tha dysplastic.…”

A promoter region of the midkine gene that is frequently expressed in human hepatocellular carcinoma can activate a suicide gene as effectively as the α-fetoprotein promoter

“…MK (Kadomatsu et al, 1988) and AFP cDNA (Morinaga et al, 1983) were labelled with [ 32 P]dCTP and used as probes. The hybridisation was performed in a solution of 50% formamide/5 Â SSC/ 50 mM NaH 2 PO 4 /2 Â Denhardt's solution/0.1% SDS/0.1 mg ml À1 salmon sperm DNA at 421C for 12 h. The filter was washed with a solution of 0.2 Â SSPE/0.1% SDS several times at 501C.…”