Cloning of bovine prolactin cDNA and evolutionary implications of its sequence

Restriction fragment length polymorphisms for growth hormone, prolactin, osteonectin, alpha crystallin, gamma crystallin, fibronectin and 21-steroid hydroxylase in cattle

Genomic DNAs from animals representing six breeds of cattle (Angus, Brahman, Hereford, Holstein, Jersey and Texas Longhorn) were screened with cloned gene probes in a search for restriction fragment length polymorphisms (RFLPs). Eleven RFLPs were identified using seven different probes: growth hormone, prolactin, osteonectin, alpha A-crystallin, gamma crystallin, fibronectin and 21-steroid hydroxylase. The frequencies of the alleles identified by each probe were calculated and compared in a limited sampling of the six bovine breeds. These polymorphisms greatly enhance the pool of immunogenetic, biochemical and molecular markers available in cattle for linkage analysis, testing of parentage, and distinction of breeds.

PLP-I: a novel prolactin-like gene in rodents

In this report, we describe molecular cloning and characterization of cDNAs encoding a novel rat prolactin-like protein. The rat cDNAs were isolated from the decidua and the gene was named PLP-I. cDNAs for the mouse equivalent were also cloned by the cross-hybridization technique. Pregnancy-specific expression of the rat PLP-I gene was observed in the rat placenta by Northern analysis. Location of signal peptide cleavage sites in rat and mouse pre-PLP-I proteins was predicted using a theoretical method. A molecular phylogenetic tree for the growth hormone-prolactin superfamily including the novel member, PLP-I, constructed using the neighbor-joining method, places rat/mouse PLP-I closest to rat/mouse placental lactogen I and II.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Sequence and regulation of European eel prolactin mRNA

cDNA clones encoding the European eel (Anguilla anguilla L.) prolactin were isolated from a pituitary cDNA library constructed in gamma gt10, using a rainbow trout Prl cDNA fragment as a probe. Four different inserts were subcloned into the pGEM 3Z plasmid after PCR amplification. The 1082 bp-long nucleotide sequence revealed an open reading frame of 627 bp encoding a 24 amino acid-long signal peptide followed by a 185 amino acid-long mature protein. Comparison studies showed 60-70% homology with other known teleost fish prolactins and 30-45% with non-teleost fish, amphibian, reptilian, avian and mammalian prolactins. In situ hybridization studies using labelled prolactin RNA probe showed a strong signal in the rostral pars distalis of the pituitary gland. We next examined the physiological regulation of this prolactin synthesis in vivo using Northern blot analysis and prolactin cDNA probe labelled by random priming. The pituitary prolactin mRNA level was markedly decreased 3 weeks after transfer of eels from freshwater to sea water. Implants of thyroid hormones left for up to three weeks were ineffective on prolactin mRNA. Estradiol administered as implant, alone or in combination with 500 micrograms testosterone, was also unable to significantly alter the pituitary mRNA level for prolactin in the freshwater silver eels whatever the dose used (20-500 micrograms) and whatever the duration of treatment (from 4 days to 10 weeks).

Molecular cloning of silver carp and bighead carp prolactin

The cDNAs encoding the prolactin of silver carp (scPRL) and bighead carp (bcPRL) have been cloned. Deduced from the nucleotide sequences, both scPRL and bcPRL are composed of 187 amino acid residues. Only one residue is different between scPRL and bcPRL. Homology analysis indicates that scPRL and bcPRL are highly homologous to carp PRL (97%), relatively conserved in relation to PRLs of salmon, trout, and tilapia (64-69%), and diversified from avian and mammalian PRL (30-35%). Similar to PRLs of other species of fish, scPRL and bcPRL lack the first 12 N-terminal residues of avian and mammalian PRLs.

Enhanced heterologous gene expression in novel rpoH mutants of Escherichia coli

Extragenic temperature-resistant suppressor mutants of an rpoD800 derivative of Escherichia coli W3110 were selected at 43.5 degrees C. Two of the mutants were shown to have a phenotype of enhanced accumulation of heterologous proteins. Genetic mapping of the two mutants showed that the mutation conferring temperature resistance resided in the rpoH gene. P1-mediated transduction of the rpoD+ gene into both of the rpoD800 rpoH double mutants resulted in viable rpoH mutants, MON102 and MON105, that retained temperature resistance at 46 degrees C, the maximum growth temperature of W3110. The complete rpoH gene, including the regulatory region, from MON102, MON105, and the parental W3110 was cloned and sequenced. Sequencing results showed that a single C----T transition at nucleotide 802 was present in both MON102 and MON105, resulting in an Arg(CGC)----Cys(TGC) substitution at amino acid residue 268 (R-268-C; this gene was designated rpoH358). Heterologous protein accumulation levels in both MON102 and MON105, as well as in rpoH358 mutants constructed in previously unmanipulated W3110 and JM101, were assessed and compared with parental W3110 and JM101 levels. Expression studies utilizing the recA or araBAD promoter and the phage T7 gene 10L ribosome-binding site (g10L) showed that increased accumulation levels of a number of representative heterologous proteins (i.e., human or bovine insulin-like growth factor-1, bovine insulin-like growth factor-2, prohormone of human atrial natriuretic factor, bovine placental lactogen, and/or bovine prolactin) were obtained in the rpoH358 mutants compared with the levels in the parental W3110 and JM101. The mechanism of enhanced heterologous protein accumulation in MON102 and MON105 was unique compared with those of previously described rpoH mutants. Pulse-chase and Northern (RNA) blot analyses showed that the enhanced accumulation of heterologous proteins was not due to decreased proteolysis but was instead due to increased levels of the respective heterologous mRNAs accompanied by increased synthesis of the respective heterologous proteins. The plasmid copy number remained unaltered.

Purification to homogeneity of bovine prolactin by high-performance ion-exchange chromatography

Homogeneous bovine prolactin (bPRL) has been obtained using a procedure based on high-performance anion-exchange chromatography. The procedure enables up to 6 mg of 99.4% pure bPRL to be obtained per hour, with a recovery of 32.4%. The purity of the protein was checked by N-terminal sequencing and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The highly purified bPRL obtained with this method is suitable for complete structural and immunochemical studies.

Structure, sequence, chromosomal location, and evolution of the human ferredoxin gene family

Ferredoxin is an iron-sulfur protein that serves as an electron transport intermediate for mitochondrial cytochromes P450 involved in steroid, vitamin D, and bile acid metabolism. We cloned and characterized the human ferredoxin gene family, which includes two expressed genes and two pseudogenes. Sequence analysis of this gene family revealed that it encodes only one protein product. The expressed genes were assigned to chromosome 11 and pseudogenes to chromosomes 20 and 21 by identifying single-copy probes from each gene segment and hybridizing them to DNA from rodent-human hybrid cells. The pseudogenes lacked introns and contained numerous mutations, including insertion, deletion, and substitution which rendered them inactive. They were 96% and 85% homologous to the expressed gene, yet they were only 78% homologous with each other. The intronless nature, higher diversity among themselves, and distinct chromosomal location of the pseudogenes suggests that they arose by independent, retroposon-mediated events.

Rainbow trout prolactin cDNA cloning in Escherichia coli

We describe the isolation and characterization of a cDNA for trout prolactin (tPrl). An extensive analysis of tPrl recombinant clones by restriction analysis and sequencing revealed the presence of only one form of tPrl mRNA. The deduced protein sequence consists of 210 amino acids, including a signal peptide of 23 amino acids. The amino acid sequence of the mature protein is compared among teleosts and mammals, showing two domains of strong similarity that may be involved in biological activity.

Cloning and sequence of the human gene for P450c17 (steroid 17 alpha-hydroxylase/17,20 lyase): similarity with the gene for P450c21

P450c17 is a single cytochrome P450 enzyme mediating both 17 alpha-hydroxylase and 17,20 lyase activities in the biosynthesis of steroid hormones. We have cloned and sequenced the human P450XVIIA1 gene lying on chromosome 10, which encodes P450c17. The gene spans 6569 bp and is divided into eight exons by seven introns. This intron/exon structure closely resembles that of the P450XXI genes encoding P450c21 (steroid 21-hydroxylase), which contain 10 exons, except that the introns dividing exons 1 and 2 and exons 4 and 5 in the P450XXI gene are absent in the P450XVII gene. Furthermore, computer modeling studies indicate the conformations of P450c17 and P450c21 are very similar. The structures of the P450XXVII and P450XXI genes are very different from other classes of P450 genes. Although the production of P450c17 is under different hormonal, ontogenic, and tissue-specific controls in various types of steroidogenic cells, the adrenal and testis transcribe the P450XVIIA1 gene into P450c17 mRNAs having the same cap sites. S1 nuclease protection experiments locate the principal cap sites as a G residue lying 22 bases 3' to an atypical TTTAAA promoter, and 82 bases 3' to a typical CAAT box. The 5'-flanking DNA contains sequences similar to consensus sequences regulated by cAMP and glucocorticoids.

Cytochrome P450c17 (steroid 17 alpha-hydroxylase/17,20 lyase): cloning of human adrenal and testis cDNAs indicates the same gene is expressed in both tissues

P450c17 is the single enzyme mediating both 17 alpha-hydroxylase (steroid 17 alpha-monooxygenase, EC 1.14.99.9) and 17,20 lyase activities in the synthesis of steroid hormones. It has been suggested that different P450c17 isozymes mediate these activities in the adrenal gland and testis. We sequenced 423 of the 509 amino acids (83%) of the porcine adrenal enzyme; based on this partial sequence, a 128-fold degenerate 17-mer was synthesized and used to screen a porcine adrenal cDNA library. This yielded a 380-base cloned cDNA, which in turn was used to isolate several human adrenal cDNAs. The longest of these, lambda hac17-2, is 1754 base pairs long and includes the full-length coding region, the complete 3'-untranslated region, and 41 bases of the 5'-untranslated region. This cDNA encodes a protein of 508 amino acids having a predicted molecular weight of 57,379.82. High-stringency screening of a human testicular cDNA library yielded a partial clone containing 1303 identical bases. RNA gel blots and nuclease S1-protection experiments confirm that the adrenal and testicular P450c17 mRNAs are indistinguishable. These data indicate that the testis possesses a P450c17 identical to that in the adrenal. The human amino acid sequence is 66.7% homologous to the corresponding regions of the porcine sequence, and the human cDNA and amino acid sequences are 80.1 and 70.3% homologous, respectively, to bovine adrenal P450c17 cDNA. Both comparisons indicate that a central region comprising amino acid residues 160-268 is hypervariable among these species of P450c17. Comparison of the amino acid sequence of P450c17 with two other human steroidogenic cytochromes P450 show much greater homology with P450c21 (28.9%), another microsomal enzyme, than with P450scc (12.3%), a mitochondrial enzyme.

Structure of genes encoding steroidogenic enzymes

Synthesis of adrenal steroid hormones from cholesterol entails the actions of only five enzymes, four of which are specific forms of cytochrome P450. These cytochrome P450 enzymes have all been isolated and their activities reconstituted in vitro, showing that each enzyme catalyses multiple steroidal conversions. Genes or complementary DNAs have been cloned for human P450scc (the cholesterol side-chain cleavage enzyme), P450c17 (17 alpha-hydroxylase/17,20 lyase) and P450c21 (21-hydroxylase). The sequences for microsomal P450c17 and P450c21 are much more closely related to one another than either is to the sequence for mitochondrial P450scc. Each of these P450 enzymes is encoded by a single human gene; the gene for P450scc lies on chromosome 15, that for P450c17 lies on chromosome 10, and that for P450c21 lies on chromosome 6. The human, mouse and bovine genomes each have two P450c21 genes. While only one of these is active in mouse and man, both genes may be active in cattle. A wide variety of lesions in the human P450c21(B) gene causes congenital adrenal hyperplasia, a common genetic disorder.

Human cholesterol side-chain cleavage enzyme, P450scc: cDNA cloning, assignment of the gene to chromosome 15, and expression in the placenta

Conversion of cholesterol to pregnenolone is mediated by P450scc [cholesterol, reduced-adrenal-ferrodoxin: oxygen oxidoreductase (side-chain-cleaving), EC 1.14.15.67]. RNA from several human adrenal samples was translated in vitro and immunoprecipitated with anti-bovine P450scc, indicating that P450scc mRNA represents about 0.5% of human adrenal mRNA in normal, hypertrophied, and malignant adrenals. A 1626-base-pair human adrenal P450scc cDNA was cloned in bacteriophage lambda gt10. Primer extension data indicated P450scc mRNA is about 1850 bases long and that all adrenal P450scc mRNA has the same 5' end. A full-length clone containing 1821 bases was obtained from a human testis cDNA library to yield the complete sequence. The encoded human preP450scc contains 521 amino acids with a molecular weight of 60189.65. The testis and adrenal sequences were identical; the human cDNA and amino acid sequences are 82% and 72% homologous, respectively, with the bovine sequences. P450scc cDNA was used to probe DNA from a panel of mouse-human somatic cell hybrids, showing that the single human P450scc gene lies on chromosome 15. The human P450scc gene is expressed in the placenta in early and midgestation; primary cultures of placental tissue indicate P450scc mRNA accumulates in response to cyclic AMP.

Cloning and sequence analysis of cDNA for mouse prolactin

The present study was undertaken to find out whether or not sexual dimorphism in biological activities and amino acid compositions of mouse prolactin might be due to heterogeneity in mRNA for mouse prolactin Cloned cDNAs for mouse prolactin were first isolated from a mouse pituitary cDNA library by hybridization with a rat prolactin cDNA. Then, one clone of about 140 positive clones obtained from 2000 transformants was subjected to nucleotide sequence analysis and verified to contain a nearly full length of cDNA sequence coding for mouse prolactin precursor. The deduced complete amino acid sequence indicates that the precursor molecule consists of 31 amino acids as the signal peptide and 197 amino acids of prolactin, in which two amino acids were found to be different from the amino acid sequence previously published elsewhere. S1 nuclease mapping analysis using male and female pituitary RNAs indicates that mouse preprolactin is encoded by two mRNAs in both sexes. The two mRNAs differ from each other based upon the deletion of three nucleotides in the coding region for the signal peptide determined by the nucleotide sequence analysis in other cDNA clones. In the present study, no sexual difference was revealed in murine prolactin mRNA.

Structure of a bovine gene for P-450c21 (steroid 21-hydroxylase) defines a novel cytochrome P-450 gene family

P-450c21, a cytochrome P-450 enzyme [steroid 21-monooxygenase (steroid 21-hydroxylase), EC 1.14.99.10], mediates the 21-hydroxylation of glucocorticoid and mineralocorticoid hormones in the adrenal gland. The complete sequence of a bovine P-450c21 gene shows it is 3447 base pairs long and contains 10 exons. The intron/exon organization and encoded amino acid sequence indicate that P-450c21 represents a unique family of genes in the P-450 gene superfamily. Primer extension and S1 nuclease protection experiments identified several cap sites for initiation of transcription; the principal cap site produces mRNA with a 5' untranslated region only 11 bases long. S1 nuclease protection experiments confirm that P-450c21 is actively expressed in the adrenal and the testis, an organ not known to secrete 21-hydroxylated steroids.

Synthesis of bovine prolactin in Escherichia coli

Transformation of Escherichia coli cells with a recombinant plasmid (pESP4) containing a modified bovine prolactin cDNA clone in a pEMBL vector resulted in efficient expression of prolactin. The cDNA was modified by removal of a 5' nontranslated sequence as well as the sequence that specified the signal peptide of preprolactin. To achieve a high level of synthesis, a sequence of 30 nucleotides in the cDNA, which included the ATG initiation codon and the first 7 codons of mature bovine prolactin, was replaced by a chemically synthesized oligonucleotide duplex. The sequence of this duplex was chosen from the consensus sequence around the initiation codon of E. coli genes and by the amino acid sequence of the protein. Prolactin, a single-chain polypeptide of molecular weight 24,000, was identified by Coomassie Blue staining of NaDodSO4-polyacrylamide gels of total protein from transformed E. coli cells, and by reaction with specific antibody. Increased levels of expression of the hormone, corresponding to the form secreted from the pituitary, were observed in the presence of isopropyl-beta-D-thiogalactopyranoside (IPTG).

Use of avian retroviral-bovine growth hormone DNA recombinants to direct expression of biologically active growth hormone by cultured fibroblasts

A variety of recombinant DNA molecules were constructed in which an avian retroviral long terminal repeat (LTR) was ligated to the bovine growth hormone (bGH) gene. The retroviral LTR was derived from a plasmid clone of a Schmidt Ruppin B strain of Rous sarcoma virus while the bGH gene was subcloned from a lambda bacteriophage genomic library. Using a transient eukaryotic expression assay system, recombinant plasmid constructs were screened for their ability to direct expression and secretion of bGH. One such plasmid DNA construct, termed pBGH-4, was found to be active in the production of bGH. Stable mouse fibroblast cell lines were generated containing pBGH-4 DNA integrated into the mouse cell genome. Many of these mouse cell lines express and secrete bGH. One line, L-Pd lambda-BGH4-13, was found to secrete bGH at a rate of 75 micrograms per 5 X 10(6) cells per 24 hr. Bovine growth hormone derived from this cell line is biologically active.

Molecular cloning of DNA complementary to bovine adrenal P450scc mRNA

P450scc is the rate-limiting hormonally regulated enzyme that cleaves the cholesterol side chain. Translation of bovine adrenocortical mRNA and immunoprecipitation with rabbit anti-bovine P450scc indicates P450scc mRNA represents 1% of the total. DNA complementary to bovine adrenocortical mRNA was cloned in the PstI site of pBR322 by dC X dG tailing and high-efficiency transformation. A clone containing sequences complementary to P450scc mRNA was identified by hybrid-selected translation only when plasmid DNA was first purified by CsCl gradient centrifugation. As is often the case with hybrid-selected translation, the clone identified contains a small insert.

Glycosylated ovine prolactin

A modification of prolactin, in which the asparagine at position 31 carries a carbohydrate unit, was isolated from ovine pituitary glands. Sequence and amino acid analyses identified the point of linkage of the carbohydrate. Glucosamine was found in acid hydrolysates, an indication that the carbohydrate is attached through N-acetylglucosamine. The glycosylated prolactin binds to concanavalin A and lentil lectin and is eluted with methyl alpha-D-mannopyranoside. During gel electrophoresis in sodium dodecyl sulfate, the glycosylated hormone migrates as a Mr 25,000 protein; prolactin has a Mr of 23,000. The modified prolactin had a potency of 20 international units/mg, approximately equal to 60% the potency of a reference prolactin preparation when measured by the pigeon crop sac assay. In a radioimmunoassay, the glycosylated form had only 34% the immunoreactivity of ovine prolactin.

Sequence of rat alpha- and gamma-casein mRNAs: evolutionary comparison of the calcium-dependent rat casein multigene family

The complete sequences of rat alpha- and gamma-casein mRNAs have been determined. The 1402-nucleotide alpha- and 864-nucleotide gamma-casein mRNAs both encode 15 amino acid signal peptides and mature proteins of 269 and 164 residues, respectively. Considerable homology between the 5' non-coding regions, and the regions encoding the signal peptides and the phosphorylation sites, in these mRNAs as compared to several other rodent casein mRNAs, was observed. Significant homology was also detected between rat alpha- and bovine alpha s1-casein. Comparison of the rodent and bovine sequences suggests that the caseins evolved at about the time of the appearance of the primitive mammals. This may have occurred by intragenic duplication of a nucleotide sequence encoding a primitive phosphorylation site, -(Ser)n-Glu-Glu-, and intergenic duplication resulting in the small casein multigene family. A unique feature of the rat alpha-casein sequence is an insertion in the coding region containing 10 repeated elements of 18 nucleotides each. This insertion appears to have occurred 7-12 million years ago, just prior to the divergence of rat and mouse.

Cloning and nucleotide sequencing of the bovine growth hormone gene

A gene coding for bovine growth hormone was isolated from a bovine genomic library. The nucleotide sequence of the coding regions of the gene was found to be identical with that of a nearly full-length growth hormone cDNA clone. The gene sequence is approximately 1800 bp in length and contains four intervening sequences. The second intervening sequence of 227 nucleotides does not contain a repetitive element similar to that observed in the rat growth hormone gene. A comparison of the 5' and 3' flanking and untranslated regions of the bovine, human and rat growth hormone genes revealed many areas of highly conserved sequence. Especially noteworthy was the observation that all three genes had a 38 nucleotide homologous sequence within their 5' flanking regions located about 100 bp upstream from their transcription initiation sites.

Rat beta casein cDNA: sequence analysis and evolutionary comparisons

The complete sequence of a 1072 nucleotide rat beta-casein cDNA insertion in the hybrid plasmid pC beta 23 has been determined. Primer extension was employed to determine the sequence of an additional 82 5'-terminal nucleotides in beta-casein mRNA. Rat beta-casein mRNA consists of a 696 nucleotide coding region, flanked by 52 nucleotide 5' and 406 nucleotide 3' noncoding regions, including a 40 nucleotide poly(A) tail. The derived 216 amino acid sequence of rat beta-casein was compared to the previously determined sequences of beta-caseins from several other species. Approximately 38% of the amino acids have been conserved among the rat, ovine, bovine and human sequences and these conserved amino acids occurred in clusters throughout the protein. One such cluster containing the majority of the potential casein phosphorylation sites was located near the amino terminus. Contrary to the considerable divergence observed for the processed beta-casein, 14 of 15 amino acids in the signal peptide sequence of the precasein were identical between the rat and ovine caseins.