Expression of the fgr protooncogene product as a function of myelomonocytic cell maturation

The fgr protooncogene is a member of the src family of protein tyrosine kinases. Recent studies have shown that normal myelomonocytic cells and tissue macrophages are the major sites of fgr mRNA expression. In the present study, we have identified the fgr protooncogene protein product in HL60 cells and have examined its expression as a function of HL60 cell maturation. Whether induced toward monocytic or granulocytic lineages, p55c-fgr accumulated in HL60 cells during maturation. In differentiated cells, the protein was active as a protein tyrosine kinase and was localized to peripheral cell membranes. Demonstration that a myristyl group was covalently bound to the protein probably accounted for its subcellular distribution. These findings establish developmental regulation of p55c-fgr in a lineage that represents its natural site of expression.     

Human tissue factor: cDNA sequence and chromosome localization of the gene

A human placenta cDNA library in lambda gt11 was screened for the expression of tissue factor antigens with rabbit polyclonal anti-human tissue factor immunoglobulin G. Among 4 million recombinant clones screened, one positive, lambda HTF8, expressed a protein that shared epitopes with authentic human brain tissue factor. The 1.1-kilobase cDNA insert of lambda HTF8 encoded a peptide that contained the amino-terminal protein sequence of human brain tissue factor. Northern blotting identified a major mRNA species of 2.2 kilobases and a minor species of approximately 3.2 kilobases in poly(A)+ RNA of placenta. Only 2.2-kilobase mRNA was detected in human brain and in the human monocytic U937 cell line. In U937 cells, the quantity of tissue factor mRNA was increased severalfold by exposure of the cells to phorbol 12-myristate 13-acetate. Additional cDNA clones were selected by hybridization with the cDNA insert of lambda HTF8. These overlapping isolates span 2177 base pairs of the tissue factor cDNA sequence that includes a 5'-noncoding region of 75 base pairs, an open reading frame of 885 base pairs, a stop codon, a 3'-noncoding region of 1141 base pairs, and a poly(A) tail. The open reading frame encodes a 33-kilodalton protein of 295 amino acids. The predicted sequence includes a signal peptide of 32 or 34 amino acids, a probable extracellular factor VII binding domain of 217 or 219 amino acids, a transmembrane segment of 23 amino acids, and a cytoplasmic tail of 21 amino acids. There are three potential glycosylation sites with the sequence Asn-X-Thr/Ser.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence for a precursor of the high-affinity metastasis-associated murine laminin receptor

The high-affinity cellular receptor for the basement membrane component laminin is differentially expressed during tumor invasion and metastasis. A cDNA clone encoding the murine laminin receptor was isolated and identified on the basis of sequence homology to the human laminin receptor [Wewer et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7137-7141]. Primer extension experiments demonstrated that the clone contained the complete 5' sequence of the murine laminin receptor mRNA. RNA blot data demonstrated a single-sized laminin receptor mRNA, approximately 1400 bases long, in human, mouse, and rat. The nascent laminin receptor predicted from the cDNA sequence is 295 amino acids long, with a molecular weight of 33,000, and contains one intradisulfide bridge, a short putative transmembrane domain, and an extracellular carboxy-terminal region which has abundant glutamic acid residues and multiple repeat sequences. The precursor of the laminin receptor is apparently smaller than the 67-kilodalton protein isolated from tissue. The apparent molecular weight on SDS-polyacrylamide gels of the rabbit reticulocyte cell-free translation product of selectively hybridized laminin receptor mRNA is 37,000. Antisera to three different domains of the cDNA-predicted receptor were used to study the relationship between the 37- and 67-kilodalton polypeptides. Antisera to cDNA-deduced synthetic peptides of the receptor immunoprecipitated a 37-kilodalton band both from cell-free translation products and from pulse-labeled cell extracts. On immunoblots of cell extracts, one antisynthetic peptide antiserum recognized only the 67-kilodalton receptor, while another antiserum identified both 37- and 67-kilodalton polypeptides, suggesting a precursor-product relationship between the two polypeptides.     

Cytovillin, a microvillar Mr 75,000 protein. cDNA sequence, prokaryotic expression, and chromosomal localization

Cytovillin is a microvillar cytoplasmic peripheral membrane protein, with prominent expression in vivo in placental syncytiotrophoblasts and certain human tumors. Cytovillin cDNA was cloned from a human placental lambda gt11 library using affinity purified antibodies. The identity of cytovillin cDNA clones was confirmed by expression of cytovillin in Escherichia coli and using antibodies raised against the expressed fusion protein in comparison with antibodies against cytovillin purified from cultured human choriocarcinoma cells. In these cells Northern blotting analysis identified a major 3.5-kilobase cytovillin mRNA. The cDNA encodes a protein of 575 amino acids corresponding to a molecular weight of 68,084. According to secondary structure prediction, cytovillin is a hydrophilic protein with an extensive internal alpha-helical region ending in a sequence of 7 consecutive prolines. The predicted alpha-helical region showed limited homology to alpha-helical regions of cytoskeletal proteins and certain other proteins, but no extensive homologies were found in the cytovillin cDNA or the deduced amino acid sequence to other registered DNA or protein sequences. Southern blot analysis of a DNA panel of human mouse somatic cell hybrids localized the cytovillin gene to the end of the long arm of chromosome 6 (6q22-q27). Our results show that cytovillin is representative of a novel class of microvillar proteins.     

Sequence of membrane-associated thyroid hormone binding protein from bovine liver: its identity with protein disulphide isomerase

The complementary DNAs of the bovine liver membrane-associated 3,5,3'-triiodo-L-thyronine binding protein with 55 k-dalton (T3BP) were cloned and the nucleotide sequences were determined. Monospecific antibodies against T3BP were used to screen a bovine liver cDNA library in lambda gtll. We analyzed the sequences of two cloned T3BP cDNAs. The clones encoded a polypeptide of 510 amino acid residues, including a signal peptide of 20 amino acid. Northern blot analysis of bovine and human RNA showed that the mRNAs encoding T3BP are 2.7 kilobase in length. Amino acid sequence of N-terminal and other three peptides isolated from purified T3BP were found in the predicted amino acid sequence from the cDNA sequence. The predicted amino acid sequence is closely homologous (93%) with that of rat protein disulphide isomerase (EC 5.3.4.1), which catalyzes the isomerization of the protein disulphide bonds and has been shown to play an important role in post-translational regulation. The results suggest that T3BP and protein disulphide isomerase should be the same protein.     

Isolation and characterization of a full-length cDNA encoding the 55-kDa rabbit zona pellucida protein.

A full-length cDNA (rc55) encoding the major rabbit zona pellucida (ZP) glycoprotein (55 kDa) has been cloned and sequenced. A lambda gt11 expression library was constructed using poly(A)+ mRNA isolated from sexually immature rabbit ovaries which contain large numbers of developing follicles. The rc55 cDNA was identified using affinity purified polyclonal antibodies specific to ZP antigens which are shared among mammalian species. The deduced amino acid sequence of the full-length rc55 clone was matched to the NH2-terminal 25-amino acid sequence obtained for this protein. The predicted amino acid sequence consists of 540 amino acids including a putative signal peptide of 18-24 residues and six potential N-glycosylation sites. The cDNA hybridizes to a 2000-base species of mRNA from rabbit ovary which is not detected in other rabbit tissues. The message is present early in ovarian follicular development and is approximately 600-fold greater in sexually immature as compared with sexually mature rabbit ovaries. This cDNA was expressed as a cro-beta-galactosidase fusion protein using the pEX expression vector. Antibodies against native rabbit ZP, affinity-purified on the recombinant 55-kDa ZP protein, were found to recognize the native rabbit ZP glycoprotein, indicating partial conservation of native epitopes in the expressed recombinant protein.     

cDNA sequence of the rat U snRNP-associated protein N: description of a potential Sm epitope.

Anti-Sm antibodies from a patient with systemic lupus erythematosus (SLE) were used to isolate cDNA clones encoding the snRNP-associated protein N from a rat brain derived cDNA library. The predicted primary structure of the 240 amino acid protein has a proline rich carboxyl terminus and shares a region of sequence similarity with other snRNP polypeptides, A and B/B'. Anti-Sm sera recognize a beta-galactosidase fusion protein containing only the carboxyl-terminal 80 amino acids of N; antibodies eluted from this fusion protein also react with A, B/B' and N on immunoblots, suggesting that these proteins share an Sm epitope located within this segment. Polyclonal antibodies raised against a 23 amino acid synthetic peptide derived from this conserved region of N recognize A, N and B/B' on immunoblots and can immunoprecipitate the Sm class of U snRNAs. These results confirm that this sequence defines a potential Sm epitope. RNA blotting analyses demonstrate that a 1.6 kb mRNA expressed predominantly in brain encodes the N polypeptide in both rats and humans. At low stringency rat N cDNA also hybridizes to a 1.3 kb mRNA species which encodes B/B', suggesting that N is structurally related to, but distinct from B/B'. Although B/B' proteins are thought to be expressed in all human cells, only N and B, but not B', are observed on immunoblots of human brain proteins probed with anti-Sm sera. The apparent difference in the complement of proteins associated with snRNP particles in human brain versus elsewhere suggests a possible mechanism for the regulation of brain-specific mRNA splicing.     

Identification from cDNA of the precursor form of a chondroitin sulfate proteoglycan core protein

The yolk sac carcinoma cell line L2 secretes a chondroitin/dermatan sulfate proteoglycan that has an Mr 10,000 core protein and carries an average of 14 glycosaminoglycan chains. The amino acid sequence of the mature core protein has been determined from cloned cDNA (Bourdon, M. A., Oldberg, A., Pierschbacher, M., and Ruoslahti, E. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 1321-1325). From additional cDNA sequences described in this report we have identified the prepro core protein precursor of the yolk sac carcinoma chondroitin/dermatan sulfate proteoglycan. From the amino acid sequence of the core protein precursor can be deduced the protein processing events in the biosynthesis of the proteoglycan. The amino acid sequence shows that the 104-amino acid mature core protein is processed from a 179-amino acid prepro core protein precursor which, in addition to the mature core protein, contains a 26-amino acid signal peptide as well as a 49-amino acid propeptide. The molecular weight of the prepro core protein predicted from the cDNA sequence (Mr = 18,600) was in good agreement with the molecular weight of the in vitro translation product (Mr = 19,000) of hybrid-selected mRNA. Accordingly, we have designated the proteoglycan core protein PG19. Further analysis of the PG19 mRNA by RNA sequencing confirmed the identification of the core protein translation initiation codon by revealing stop codons in all three reading frames of the upstream mRNA sequence. Primer extension analyses demonstrated that the 5' untranslated sequence of the proteoglycan mRNA is approximately 220 nucleotides in length, which, combined with the length of cDNA clones, accounts for the entire length of the coding sequence of PG19 mRNA from L2 cells. The cDNA sequences presented here establish the complete protein sequence of PG19 and provide evidence of polypeptide processing during the biosynthesis of the proteoglycan core protein.     

Molecular cloning of the human B cell CD20 receptor predicts a hydrophobic protein with multiple transmembrane domains.

CD20 is an antigen expressed on normal and malignant human B cells that is thought to function as a receptor during B cell activation. Here we report the isolation of a CD20-specific cDNA clone from a lambda gt11 library using a polyclonal antiserum raised against purified CD20 antigen. Additional cDNA clones were then isolated from a lambda gt10 library. Alignment of the sequences of overlapping lambda clones reveal a single consensus sequence except for a divergence that preceded the first methionine within the open reading frame. Normal B cells and B cell lines contain a prominent 2.6 kb mRNA and a lower level of a 3.3 kb mRNA. An oligonucleotide derived from one of the divergent sequences hybridized to the 3.3 kb mRNA only, indicating that the two mRNA species are derived from an alternative splicing mechanism. The predicted amino acid sequence of CD20 reveals three major hydrophobic regions of approximately 53, 25 and 20 amino acids. CD20 lacks an NH2-terminal signal peptide and contains a highly charged COOH-terminal domain. Although CD20 is immunoprecipitated as a doublet of 33 and 35 kd proteins from B cells, in vitro translation of CD20 cDNA produced a single 33 kd protein that was specifically immunoprecipitated with monoclonal CD20 antibodies. CD20 was strongly phosphorylated on resting B cells after CDw40 stimulation, suggesting that CD20 may be functionally regulated by a protein kinase(s).     

Molecular cloning and sequence analysis of cDNA for human hepatocyte growth factor

Amino acid sequences of four peptide fragments of human hepatocyte growth factor purified from the plasma of patients with fulminant hepatic failure were determined. Based on the amino acid sequence of one of the fragments, two oligodeoxyribonucleotide mixtures were synthesized and used to screen a human placenta cDNA library. On the screening, two overlapping cDNA clones for human hepatocyte growth factor were isolated and the nucleotide sequence of the cDNA was determined. The entire primary structure of the protein was deduced from the sequence. The protein consists of 728 amino acid residues, including a possible signal peptide at the N-terminus. The sequence revealed that the heavy and light chains which comprise the protein are encoded by the same mRNA and are produced from a common translation product by proteolytic processing.     

A form of human basic fibroblast growth factor with an extended amino terminus

The amino acid sequence of a human placental bFGF was determined by a combination of protein and cDNA sequencing. The placental bFGF consists of 157 amino acid residues with a calculated molecular weight of 17,464 and is highly homologous to bovine pituitary bFGF. The human protein contains an amino terminal extension when compared to the sequence established for bovine bFGF (Esch et al., 1985) and to the sequence of the predicted translation product based on human bFGF cDNA clones (Abraham et al., 1986).     

Human thrombomodulin: complete cDNA sequence and chromosome localization of the gene

A human umbilical vein endothelial cell cDNA library in lambda gt11 was screened for expression of thrombomodulin antigens with affinity-purified rabbit polyclonal anti-thrombomodulin immunoglobulin G (IgG) and mouse monoclonal anti-human thrombomodulin IgG. Among 7 million recombinant clones screened, 12 were recognized by both antibodies. Two of these, lambda HTm10 and lambda HTm12, were shown to encode thrombomodulin by comparison of the amino acid sequence deduced from the nucleotide sequence to the amino acid sequence determined directly from tryptic peptides of thrombomodulin. Thrombomodulin mRNA was estimated to be 3.7 kilobases in length by Northern blot analysis of endothelial cell and placental poly(A)+ RNA. Thrombomodulin mRNA was not detected in human brain, HepG2 hepatoma cells, or the monocytic U937 cell line. Additional cDNA clones were selected by hybridization with the 1.2-kilobase insert of lambda HTm10. One isolate, lambda HTm15, contained a 3693 base pair cDNA insert with an apparent 5'-noncoding region of 146 base pairs, an open reading frame of 1725 base pairs, a stop codon, a 3'-noncoding region of 1779 base pairs, and a poly(A) tail of 40 base pairs. The cDNA sequence encodes a 60.3-kDa protein of 575 amino acids. The predicted protein sequence includes a signal peptide of approximately 21 amino acids, an amino-terminal ligand-binding domain of approximately 223 amino acids, an epidermal growth factor (EGF) homology region of 236 amino acids, a serine/threonine-rich segment of 34 amino acids, a membrane-spanning domain of 23 amino acids, and a cytoplasmic tail of 38 amino acids. The EGF-homology region consists of six tandemly repeated EGF-like domains.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cloning and characterization of a cDNA coding for the lipoprotein-associated coagulation inhibitor shows that it consists of three tandem Kunitz-type inhibitory domains

Human plasma contains a lipoprotein-associated coagulation inhibitor (LACI) which inactivates factor Xa directly, and in a Xa-dependent fashion also inhibits the VIIa-tissue factor complex of the extrinsic coagulation pathway. Rabbit polyclonal anti-LACI antiserum was used to screen human placental and fetal liver lambda gt11 cDNA libraries for the expression of LACI antigens. Immunologically positive clones were further tested for their ability to bind 125I-factor Xa. Seven clones were obtained which are immunologically and functionally active. The longest cDNA insert (lambda P9) of these isolates is 1.4 kilobases (kb) while other clones are 1.0 kb in length. Nucleotide sequence analysis shows that lambda P9 consists of 1431 bases that include a 5'-noncoding sequence of 132 nucleotides, an open reading frame of 912 nucleotides, and a 3'-noncoding region of 387 nucleotides. The open reading frame encodes a signal peptide of 28 residues followed by a 32-kilodalton protein of 276 residues. The predicted sequence of mature LACI contains 18 cysteines and three potential N-linked glycosylation sites. The amino acid sequence analysis of purified LACI's NH2 terminus and two of its proteolytic fragments match exactly those deduced from the cDNA sequence, indicating that the cDNA codes for LACI. The translated amino acid sequence of LACI shows several discernible domains, including a highly negatively charged NH2 terminus, three tandem Kunitz-type inhibitory domains, and a highly positively charged carboxyl terminus. Northern blot analysis shows that the following liver-derived cell lines, Chang liver, HepG2 hepatoma, and SK hepatoma all, contain two major species of mRNA (1.4 and 4.4 kb) which hybridize with LACI cDNA.     

Human apolipoprotein A-II: complete nucleic acid sequence of preproapoA-II

The complete cDNA nucleic acid sequence of preproapolipoprotein (apo) A-II, a major protein constituent of high density lipoproteins, has been determined on clones from a human liver ds-cDNA library. Clones containing ds-cDNA for apoA-II were identified in the human liver ds-cDNA library using synthetic oligonucleotides as probes. Of 3200 clones screened, 4 reacted with the oligonucleotide probes. The DNA sequence coding for amino acids ?17 to +17 of apoA-II were determined by Maxam-Gilbert sequence analysis of restriction fragments isolated from one of these clones, pMDB2049. The remainder of the cDNA sequence was established by sequence analysis of a primer extension product synthesized utilizing a restriction fragment near the 5'-end of clone pMDB2049 as primer with total liver mRNA. The apoA-II mRNA encodes for a 100 amino acid protein, preproapoA-II that has an 18 amino acid prepeptide and a 5 amino acid propeptide terminating with a basic dipeptide (Arg-Arg) at the cleavage site to mature apoA-II.