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Secretion of human epidermal growth factor from Saccharomyces cerevisiae using synthetic leader sequences.

We have investigated different leader sequences for their ability to direct the efficient secretion of human epidermal growth factor (hEGF) from Saccharomyces cerevisiae. We designed a consensus signal sequence which directs secretion of hEGF from yeast as efficiently as the yeast invertase signal sequence. However, secretion is increased over fivefold by the introduction, after the signal sequence, of a synthetic 19-amino acid (aa) pro-sequence containing a cleavage recognition site for the KEX2 protease. Even in the absence of an Asn-linked glycosylation site, secretion of hEGF using the synthetic prepro-leader was as efficient as that directed by the alpha-factor leader. The role of the KEX2 protease cleavage site was investigated by mutation of the yeast alpha-factor KEX2 site (cleavage after Lys-Arg). Cleavage was obtained with the following order of efficiency, Lys-Arg greater than Pro-Arg greater than Asp-Arg, although the sequence context was also found to affect efficiency.

Amino Acid Sequence↗

Comparison of dose-response curves for alpha factor-induced cell division arrest, agglutination, and projection formation of yeast cells. Implication for the mechanism of alpha factor action.

MAT alpha cells of the yeast Saccharomyces cerevisiae produce a polypeptide mating pheromone, alpha factor. MATa cells respond to the pheromone by undergoing several inducible responses: the arrest of cell division, the production of a cell surface agglutinin, and the formation of one or more projections on the cell surface commonly termed the "shmoo" morphology. Dose-response curves were determined for each of these inducible responses as a function of alpha factor concentration. It is shown that under conditions commonly employed in previous studies, the dose-response for cell division arrest is determined by the rate at which cells inactivate the alpha factor. In order to achieve conditions where inactivation would not be the dominant parameter, the cell division response to alpha factor was monitored at low cell densities. Under conditions of essentially no alpha factor destruction, the dose of alpha factor at which cells exhibit a half-maximal response for cell division arrest (2.5 X 10(-10) M) is nearly the same as that at which cells exhibit a half-maximal response for agglutination induction (1.0 X 10(-10) M). On the contrary, the half-maximal response for projection formation was obtained at doses of alpha factor 2 orders of magnitude higher (1.4 X 10(-8) M). These results are consistent with the same high affinity alpha factor receptor mediating both cell division arrest and agglutination induction. A different system of lower affinity must mediate projection formation. Alternatively, if the same system and receptor are used, then a much higher occupancy is required for the induction of projections compared to division arrest and agglutination induction.

Agglutinins↗

Assessment of a new instrument (Coag-A-Mate X2) for performing global clotting tests and specific factor assays.

Coag-A-Mate X2 (General Diagnostics) is an automated photo-optical system for detection of clots, which can be used for measuring prothrombin time (PT) and activated partial thromboplastin time (APTT) and assaying coagulation factors. We have compared results obtained with this instrument with those obtained by the manual method used routinely in our specialized laboratory. The instrumental results showed good precision (PT: between-assay CV from 1.3 to 3.0, APTT: from 2.2 to 3.1), and high degree of correlation with the manual results (for PT r = 0.99, for APTT r = 0.95). There was also good correlation between the two methods (0.98-0.99) for factor assays (V, VII, VIII, IX, X, XI, and XII). High output, reproducibility, comparability and flexibility make this instrument suitable for both clinical and research laboratories.

Autoanalysis↗

FAR1 links the signal transduction pathway to the cell cycle machinery in yeast.

Alpha factor induces arrest of yeast a cells in G1 and transcription of genes involved in mating. Prior work indicates that FUS3, a member of the MAP kinase family, and FAR1, whose molecular activity is unknown, contribute to cell cycle arrest by inhibiting G1 cyclins. Here we show that FAR1 is a substrate for FUS3 and that this phosphorylation regulates association of FAR1 with CDC28-CLN2 kinase. We show also that FAR1 is phosphorylated in vitro by the CDC28-CLN2 complex and in vivo in a CDC28-dependent manner. Mutational analysis of FAR1 reveals a correlation between its ability to associate with CDC28-CLN2 and to arrest the cell cycle. These results suggest that FAR1 protein is the link between the signaling pathway and the cell cycle machinery.

Amino Acid Sequence↗

Factor X fusion proteins: improved production and use in the release in vitro of biologically active hirudin from an inactive alpha-factor-hirudin fusion protein.

Many recombinant proteins are synthesized as fusion proteins containing affinity tags to aid in the downstream processing. After purification, the affinity tag is often removed by using a site-specific protease such as factor Xa (FXa). However, the use of FXa is limited by its expense and availability from plasma. To develop a recombinant source of FXa, we have expressed two novel forms of FXa using baby hamster kidney (BHK) cells as host and the expression vector pNUT. The chimeric protein FIIFX consisted of the prepropeptide and the Gla domain of prothrombin linked to the activation peptide and protease region of FXa, together with a cellulose-binding domain (CBD(Cex)) as an affinity tag. A second variant consisted of the transferrin signal peptide linked to the second epidermal growth factor-like domain and the catalytic domain of FX and a polyhistidine tag. Both FX variants were secreted into the medium, their affinity tags were functional, and following activation, both retained FXa-specific proteolytic activity. However, the yield of the FIIFX-CBD(Cex) fusion protein was 10-fold higher than that of FX-CBD(Cex) and other forms of recombinant FX reported to date. The FXa derivatives were used to cleave two different fusion proteins, including a biologically inactive alpha-factor-hirudin fusion protein secreted by Saccharomyces cerevisiae. After cleavage, the released hirudin demonstrated biological activity in a thrombin inhibition assay, suggesting that this method may be applicable to the production of toxic or unstable proteins. The availability of novel FX derivatives linked to different affinity tags allows the development of a versatile system for processing fusion proteins in vitro.

Amino Acid Sequence↗

The ARD1 gene of yeast functions in the switch between the mitotic cell cycle and alternative developmental pathways.

Mutations in the yeast gene ARD1 lead to inability to respond to alpha-factor, inability to enter stationary phase, and inability to sporulate, suggesting an important role for the ARD1 gene product in controlling the switch between the mitotic cell cycle and alternative cell fates. MATa, ard1 cells seem to be defective in the expression of all a-specific functions, whereas MAT alpha, ard1 cells respond normally to a-factor. We propose that ARD1 is required for the expression of genes involved in a-mating functions, stationary phase, and sporulation. The ARD1 gene has been cloned and sequenced; there is weak homology between the C terminus of the ARD1 protein, the C-terminal region of MAT alpha 2, and the homeo box.

Base Sequence↗

Yeast-prepro-alpha-factor-leader-region-directed synthesis and secretion of truncated human macrophage colony-stimulating factor in the silkworm Bombyx mori.

Human macrophage colony-stimulating factor (hM-CSF) cDNA joined to the leader region of the precursor of the yeast mating pheromone alpha-factor (MF alpha L) was expressed at high levels in BmN cells and in silkworm (Bombyx mori) larvae, using recombinant Bombyx mori nuclear polyhedrosis virus, as a vector. The biological activity of rhM-CSF detected in the haemolymph was 1 x 10(6) colony-formation units/ml, approximately half of the expression level directed by the native signal peptide of hM-CSF in silkworm larvae. The secreted rhM-CSF was purified to homogeneity. N-terminal analysis showed that the signal peptide had been removed, indicating that insect cells possess the enzymic activity necessary to cleave the pro-alpha-factor leader region from the fusion protein at the carboxy side of Lys-Arg dibasic residues, which is the cleavage site recognized by KEX2 endopeptidase in yeast cells.

Amino Acid Sequence↗

Factors and their origins in mate selection and choice among humans: implications for individual psychotherapy and counseling.

A mechanism of mate selection in humans is proposed and elaborated. It is further proposed that this mechanism constitutes one of the important factors for stability and the necessary longevity of the procreational dyad and therefore the procreational success of humans as a species. The concepts and mechanisms of assortative mating (homogamy) and that of complementarity of temperaments of the mates (heterogamy) which guide such selections are described, the relationships between the two are explored, and finally their possible early developmental origins are proposed. Evidence from a small study of 20 married couples' responses in temperament tests is offered as well as some illustrative case histories all pointing to those mechanisms. The argument is based mainly on principles of evolutionary psychology.

Adult↗

Population structure of the Jirels: patterns of mate choice.

The influence of mating practices on genetic structure has been an area of great interest for anthropologists. In this paper, the techniques of potential mates analysis are employed to explore the mating patterns observed among the Jirels, a tribal population of eastern Nepal. Genealogical, anthropometric, dermatoglyphic, and demographic data for members of seven Jirel villages are used. Potential mate pools for a sample of 268 females are enumerated by village. Age structure and the Jirel restriction against clan endogamy are found to severely limit the number of males who are potential mates for a given female. The mating structure of the population is illuminated by statistical analysis of the characteristics of 160 actual mate pairs and all corresponding potential mate pairs. Using this approach several general mate choice practices were verified: 1) biological kin tend to be avoided as mates, 2) members of the same clan are excluded as potential mates, 3) mate exchange between clans is nonrandom, 4) individuals similar in age tend to be selected as mates, and 5) mates are drawn from the natal village more often than random expectation. A multivariate phenotypic distance measure between individuals did not reveal any evidence for assortative mating for either anthropometric or dermatoglyphic characters.

Age Factors↗

The norm for perceived husband superiority: a cause of human assortative marriage.

I have suggested that human assortative marriage for a number of variables is partially caused by behavior in accordance with two norms. Epstein and Guttman (1987) have suggested that there is no empirical evidence for these norms. In this note evidence is reviewed for the norm of perceived husband-superiority. Others have shown that the evidence for this norm is strong in regard to height, and it is shown here that the evidence is strong also in regard to age. Evidence for the norm seems suggestive in regard to IQ, education, and social class, and nonexistent in regard to physical attractiveness. With respect to height, it seems that the magnitude of the correlation between spouses is associated with the size of the breeding population to which they belong. Thus, it seems likely that the hypothesized norms are learned rather than genetically coded.

Adolescent↗

Pheromone-induced degradation of Ste12 contributes to signal attenuation and the specificity of developmental fate.

The Ste12 transcription factor of Saccharomyces cerevisiae regulates transcription programs controlling two different developmental fates. One is differentiation into a mating-competent form that occurs in response to mating pheromone. The other is the transition to a filamentous-growth form that occurs in response to nutrient deprivation. These two distinct roles for Ste12 make it a focus for studies into regulatory mechanisms that impart biological specificity. The transient signal characteristic of mating differentiation led us to test the hypothesis that regulation of Ste12 turnover might contribute to attenuation of the mating-specific transcription program and restrict activation of the filamentation program. We show that prolonged pheromone induction leads to ubiquitin-mediated destabilization and decreased amounts of Ste12. This depletion in pheromone-stimulated cultures is dependent on the mating-pathway-dedicated mitogen-activated protein kinase Fus3 and its target Cdc28 inhibitor, Far1. Attenuation of pheromone-induced mating-specific gene transcription (FUS1) temporally correlates with Ste12 depletion. This attenuation is abrogated in the deletion backgrounds (fus3Delta or far1Delta) where Ste12 is found to persist. Additionally, pheromone induces haploid invasion and filamentous-like growth instead of mating differentiation when Ste12 levels remain high. These observations indicate that loss of Ste12 reinforces the adaptive response to pheromone and contributes to the curtailing of a filamentation response.

Base Sequence↗

Expression of EGF and HIV envelope glycoprotein.

1. The S. cerevisiae alpha-factor prepro leader is functional and is correctly processed in P. pastoris. 2. P. pastoris has a high secretory capacity, but yields can be severely reduced by extracellular proteases. This problem can be reduced by altering the medium composition, e.g., adjusting the pH or by adding casamino acids. 3. A rapid DNA dot-blot technique can be used for mass screening of transformants to obtain high-copy-number, high-expressing strains. 4. For mEGF, which is an efficiently secreted protein, there was a good correlation between gene dosage and yield, and maximum levels were obtained at high copy number. 5. Vectors conferring resistance to G418 have been developed for the selection of high-copy-number transformants. These vectors can also be used to isolate a series of transformants with increasing copy number of optimizing the expression of genes where high copy number may be detrimental. 6. The HIV-1 ENV gene was not expressed in P. pastoris owing to fortuitous termination of transcription within AT-rich regions. This is a species-specific phenomenon, since full-length HIV-1 ENV transcripts are produced in S. cerevisiae. The problem was overcome by synthesizing the relevent portion of the gene with increased GC content. 7. ENV was hyperglycosylated and immunologically inactive when secreted by P. pastoris. The yield was reduced by extracellular proteases, but like mEGF, this could be significantly improved by altering the pH of the culture medium and by adding casamino acids. 8. In single-copy integrants, transcripts from the semisynthetic HIV-1 ENV gene were almost as abundant as endogenous AOX1. Transcript levels increased progressively with increasing copy number, showing that the AOX1 promoter is not greatly limited by the level of trans-activating factors.

Animals↗

Increased frequency of coronary heart disease in relatives of wives of myocardial infarct survivors: assortative mating for lifestyle and risk factors?

The frequency of myocardial infarction (MI) and coronary artery disease (CAD) was studied among the first-degree relatives of 126 spouses of male survivors of MI, and compared with the frequency of MI and CAD among relatives of 126 age-matched control subjects. MI and CAD were as frequent among the relatives of the wives as among the relatives of their husbands with MI. MI and CAD were less frequent among the relatives of control subjects. Familial aggregation of CAD, therefore, is not limited to patients' relatives, but also affects the wives' families. This finding can be explained by assortative mating, i.e., marriage partners choose mates with similar lifestyles and risk factors that lead to CAD.

Adult↗

Isolation and characterization of four related peptides exhibiting alpha factor activity from Saccharomyces cerevisiae.

The molecular structure of alpha factor, a mating hormone produced by alpha mating type cells of Saccharomyces cerevisiae has been investigated. From culture filtrates of alpha cells four oligopeptides exhibiting alpha factor activity have been isolated. These peptides, designated as alpha1, alpha2, alpha3, and alpha4 are structurally closely related, being composed of thirteen (alpha1 and alpha3) and twelve (alpha2 and alpha4) amino acids, respectively. The peptides were found to be composed of the following amino acids: 2 glutamic acid or glutamine, 2 proline, 1 glycine, 1 methionine or methionine sulfoxide, 2 leucine, 1 tyrosine, 1 lysine, 1 histidine, 1 or 2 tryptophan. The tridekapeptides differ from the dodekapeptides by an additional NH2-terminal tryptophan residue. Tyrosine was identified as the C-terminal amino acid in all four peptides. alpha3 and alpha4 are oxidation products containing an internal methionine sulfoxide instead of methionine. The mechanisms which could introduce the observed heterogeneity of the peptides are discussed.

Amino Acid Sequence↗