In vitro translation of RNA from lizard epididymis and identification of poly A RNA coding for a major androgen-dependent protein

During the reproductive period (spring) the lizard epididymis secretes a soluble protein of an apparent molecular weight (MW) of 19,000, the protein L. This androgen dependent protein disappears during post-nuptial atrophy of the epididymis (summer). At two time intervals (spring and summer) total RNA were extracted and poly (A) RNA were prepared. The RNA were translated in a cell-free system (rabbit reticulocyte lysate) in the presence of 35S methionine. Labelled translation products were analyzed by polyacrylamide gel electrophoresis under denaturing conditions. Electrophoresis were preceded or not by immunoprecipitation with an antiserum raised against protein L. RNA extracted during spring coded for several unique bands including five immunoprecipitated proteins with close-related MW (21,000 to 25,000). When RNA were translated in the presence of dog microsomes, the five previously detected protein bands disappear although a 19,000 MW immunoprecipitated protein was clearly demonstrated. These proteins were not detected when RNA extracted in summer were used. The protein L appears to be synthesized as preprotein(s). Its (unique or several?) messenger is of poly A type; it is present in spring and absent or undetectable in these experimental conditions in summer.     

Changes in epididymal protein synthesis during the sexual cycle of the lizard, Lacerta vivipara

During its annual cycle, the lizard epididymis undergoes strong modifications of the secretory epithelium. These modifications previously were classified into 10 stages. The present study gives the biochemical basis of these modifications. Several parameters, such as the quantity of soluble proteins, rates of protein synthesis, and electrophoretic profiles of newly synthesized proteins and of in vitro RNA translation products were compared at 8 stages. Two-dimensional gel electrophoresis of newly synthesized tissue proteins showed that the synthesis of about 20 proteins fluctuated during the cycle. Furthermore, it revealed that the protein band L of molecular weight 19,000 identified in one-dimensional (1-D) electrophoresis was composed of at least 10 proteins. Their rate of synthesis paralleled the concentrations of their mRNA evaluated with in vitro translation. This could indicate that in this system protein synthesis is regulated by mRNA concentrations. The present analysis has confirmed that 4 different phases characterize the annual evolution of the lizard epididymis: regeneration, onset of secretory activity, hypersecretion and involution. Well-defined, newly synthesized proteins would characterize some of these phases, and could be used as markers for future detailed analysis of epididymis control.     

Characterization of hormonally regulated secretory proteins from the caput epididymidis of the rabbit.

1. The incorporation of [35S]methionine into protein was investigated in tissue minces from different regions of the rabbit epididymis incubated in vitro. Rates of synthesis were in the order: epididymal regions 2-5 greater than region 7 greater than region 6 greater than region 1 greater than region 8 greater than ductus deferens greater than ductuli efferentes. 2. Separation of labelled proteins on polyacrylamide gels containing sodium dodecyl sulphate followed by fluorography revealed that one protein (mol.wt. approx. 90 000) was characteristic of region 1, four proteins (one of mol.wt. 54 000 and three of mol.wt. 20 000) were synthesized principally in regions 2-5, and one protein (mol.wt. 22 500) was produced mainly in regions 6, 7 and 8. 3. Castration for 14 days decreased incorporation of [35S]methionine into total protein to less than 10% of that in controls in all regions of the epididymis. However, testosterone treatment for a further period of 14 days restored protein synthesis to normal values in regions 6, 7 and 8, but not in region 1 or regions 2-5. In regions 2-5 the synthesis of three proteins of mol.wt. 20 000 declined after castration, but was not stimulated by exogenous testosterone. Since the 20 000-mol.wt. proteins were major tissue proteins, accounting for 16-25% of the total synthesized, they were used as markers for investigating hormone action in the epididymis. 4. Castration followed immediately by testosterone treatment or ligation of the ductuli efferentes resulted in a decrease in their synthesis, suggesting that they are partially dependent on factors in testicular fluid. Purification and characterization showed them to be acidic glycoproteins with a number of biochemical and immunological properties in common. 5. It is suggested that there is a synergistic action between blood androgens and factors in testicular fluid in regulating protein synthesis in the proximal regions of the rabbit epididymis.     

SDS-PAGE analysis of caput epididymis proteins in rats receiving a zinc deficient diet

Caput epididymis proteins from control, pairfed and zinc deficient (ZD) wistar weanling albino rats after 2-, 4-, 6- and 8-weeks were examined using SDS-PAGE followed by densitometric scanning of the gels. In comparison to the control and pairfed rats, ZD rats displayed new proteins. These included a Mr 42 kDa from 2ZD, Mr 47.5, 27.5, 23.2 and 16.0 kDa from 4ZD and Mr 87 and 14.2 kDa from 6ZD group. The 8ZD group, however, revealed no additional protein bands over controls. Further, several other proteins were missing from ZD rats. These included Mr 93 and 71 kDa from 2ZD; 93, 90, 79, 67, 62, 55 and 15.3 kDa from 4ZD; 60, 45.5, 34, 30 and 24 kDa from 6ZD and 41.5, 33 and 27.5 kDa bands from 8ZD group. The results indicate that the induced Zn-deficient state may be responsible for the altered protein patterns in the caput epididymis. The duration of low Zn uptake period also appears to influence the protein pattern in caput epididymis.     

Free messenger ribonucleoprotein complexes of chicken primary muscle cells following modification of protein synthesis by heat-shock treatment

When primary cultures of chicken myoblasts were subjected to incubation at a temperature higher than their normal growing temperature of 36-37 degrees C, the pattern of protein synthesis was altered. This condition of heat shock induced a vigorous production of a number of proteins collectively known as 'heat-shock proteins'. The synthesis of heat-shock proteins was achieved without a significant decrease in the production of a broad spectrum of proteins by muscle cells. The synthesis of three major heat-shock polypeptides with Mr values of 81 000, 65 000 and 25 000 was observed in both mononucleated dividing myoblast cells and terminally differentiated myotubes. Two-dimensional electrophoretic separation of the heat-induced polypeptides synthesized by myogenetic cultures further established that same set of polypeptides with Mr of 65 000 (pI 6.0 and 5.5), 81 000 (pI 6.2) and 25 000 (pI 5.6 and 5.3) were produced in myoblasts and myotubes. The effect of the changes in pattern of protein synthesis on the mRNA and protein moieties of non-polysomal cytoplasmic mRNA-protein complexes (free mRNP) was examined. Free mRNP complexes sedimenting at 20-35 S were isolated from the post-ribosomal supernatant of both normal and heat-shocked myotube cultures by centrifugation in a sucrose gradient. A 10-20S RNA fraction isolated from these complexes stimulated protein synthesis in a cell-free system. The RNA fraction obtained from heat-shocked cells appeared to direct the synthesis of all three major heat-shock proteins. In contrast, synthesis of these polypeptides was not detected when RNA from free mRNP complexes of normal cells was used for translation. The free mRNP complexes of both normal and heat-shocked cells showed a buoyant density of 1.195 g/cm3 in metrizamide gradients. A large number of polypeptides of Mr = 35 000-105 000 were present in the highly purified free mRNP complexes isolated from the metrizamide gradient. Similar sets of polypeptides were found in these complexes from both normal and heat-shocked myotube culture. However, the relative proportion of a 65 000-Mr polypeptide was dramatically increased in the free mRNP complexes of heat-shocked cells. Two-dimensional gel electrophoretic analysis revealed that this polypeptide and the 65 000-Mr heat-shock polypeptide exhibit similar electrophoretic migration properties. These observations suggest that, following heat-shock treatment of chicken myotube cultures, the changes in the pattern of protein synthesis is accompanied by alteration of the mRNA and protein composition of free mRNP complexes.     

Acetyl-coenzyme A carboxylase from avocado (Persea americana) plastids and spinach (Spinacia oleracea) chloroplasts.

1. Protein synthesis has been investigated in different regions of the rat epididymis by measuring incorporation of [35S]methionine in tissue minces incubated in vitro followed by analysis of labelled proteins on polyacrylamide gels containing sodium dodecyl sulphate. Rates of synthesis were highest in the proximal cauda > distal cauda > initial segment > ductuli efferentes > corpus > distal caput > proximal caput. One protein (mol.wt. 23 000) characterized the initial segment, three proteins (mol.wts. 18 500, 19 000 and 32 000) the caput and one protein (mol.wt. 47 000) the cauda. 2. After castration, [35S]methionine incorporation in all regions of the epididymis was reduced to < 10% of that in normal animals but could be restored to control levels within 5 days by testosterone treatment. Other steroids (corticosterone, oestrogen or progesterone) were ineffective. 3. The synthesis of the 18 500, 19 000, and 32 000 mol.wt. proteins in the caput and the 47 000 mol.wt. protein in the cauda were preferentially regulated by androgens, whilst the synthesis of 23 000 and approx. 80 000 mol.wt. proteins in the initial segment was dependent upon factors present in testicular fluid. 4. The androgen-dependent and testicular fluid-dependent proteins were major components of epididymal secretion. Purification and characterization of the 18 500, 19 000, 23 000 and 32 000 mol.wt. proteins showed them to be acidic glycoproteins with a carbohydrate content of 7.6-13.2%. The 47 000 mol.wt. protein, on the other hand, is highly basic. 5. A possible role for these proteins in the acquisition of motility, fertilizing capacity and storage of spermatozoa in the epididymis is discussed.     

Induction of four proteins in chick embryo cells by sodium arsenite

Four proteins of Mr = 89,000, 73,000, 35,000, and 27,000 are strongly induced in chick fibroblasts by sodium arsenite. Induction of these proteins is discoordinate as a function of arsenite concentration. Kinetically, all species appear 1 h after exposure to 50 microM arsenite, after 24 and 48 h of exposure, the 27,000 protein is still synthesized extensively, whereas normal cell proteins and the three other induced proteins are greatly reduced. The four proteins are unrelated by tryptic peptide-mapping procedures. Multiple subspecies of p89, p73, and p27 were observed in two-dimensional gels. The subspecies of p73 appear to be related as determined by partial proteolytic maps as are those of p27. Two-dimensional gel analysis of in vitro translation products from rabbit reticulocyte lysates primed with mRNA from uninduced and induced cells reveals that the amount of translatable mRNA specific for these proteins is increase by induction. This increase is attributable to new mRNA synthesis since actinomycin D prevent induction and new bands of RNA (Mr = 0.9 X 10(6) and 1.3 X 10(6)) appear in methyl mercury gels of oligo(dT) selected RNA from induced cells. These bands are assigned to p73 and p89 based on translation of electroeluted RNA from a similar preparative gel. A comparison is made between induction of these proteins and the heat shock response in Drosophilla melanogaster.     

Rabbit epididymal secretory proteins. I. Characterization and hormonal regulation

Analyses of samples of luminal fluid from the rete testis, distal efferent ducts, and epididymal regions 2-5 and 8 revealed that 91% of the fluid leaving the testis is reabsorbed by the efferent ducts, 79% of the remainder is reabsorbed proximal to epididymal regions 4 and 5, and there is a net secretion of fluid into the duct caudally. There is a net reabsorption by the efferent ducts of 73% of the protein leaving the testis and then a net secretion along the epididymis. SDS-PAGE of the luminal fluids indicated that four new protein bands that were not present in blood appeared in the efferent ducts, 5 in epididymal regions 1-5, 6 in regions 6 and 7, and one in region 8. Two bands in samples from the efferent ducts were absent caudally, and one band present in region 7 was absent in region 8. The rates of incorporation of (35)S-methionine into minced duct in vitro varied among regions when expressed per milligram of wet weight of tissue (region 2-5 > region 7 > region 6 > region 1 > region 8 > ductuli efferentes), and orchidectomy had little effect on the rates. Incorporation into four proteins that were secreted in vitro (M(r) 38 000, 20 000, 15 000, and 13 000) was reduced or abolished by orchidectomy and restored by testosterone therapy. The secretion of three proteins (M(r) 52 000, 23 000, and 22 000) was reduced or abolished by orchidectomy and not restored by testosterone therapy. SDS-PAGE of detergent extracts of sperm indicated that five proteins were lost and nine were gained during epididymal transit. Seven of the proteins gained were about the same molecular weight as proteins secreted by the epididymis (M(r) 94 000, 52 000, 38 000, 36 000, 22 000, 20 000, and 13 000) and were analyzed using N-terminal amino acid microsequencing.     

Identification and cytogenetic localization of vitelline membrane messenger RNAs in Drosophila

During stages 9 and 10 of oogenesis in Drosophila the major proteins involved in vitelline membrane (VM) formation are synthesized and secreted by the somatic follicle cells surrounding the oocyte. To identify potential mRNAs involved in VM protein synthesis, newly synthesized poly(A)-containing RNA from egg chambers of different developmental stages was studied. Urea-agarose gel electrophoresis revealed two RNA bands in stage 10 egg chambers in the size range expected for those which encode the smaller VM proteins. These RNA bands, T₁ and T₂, are specifically enriched in stage 10 follicle cell preparations. In vitro translations in reticulocyte lysates in the absence and presence of microsomal membranes showed both RNA bands code for products that are synthesized in precursor forms which are processed to species that comigrate with VM proteins. T₂ directed the synthesis of processed species that comigrated with the 23- to 24-kDa and 17.5-kDa VM proteins (J. Fargnoli and G. L. Waring, 1982, Dev. Biol. 92, 306–314) while the T₁ translation product comigrated with the 14-kDa protein. To determine the cytogenetic location of the genes encoding T₁ and T₂ RNAs, radiolabeled T₁ and T₂ RNAs were hybridized in situ to salivary gland chromosomes. The results suggest that the structural genes coding for the small vitelline membrane proteins are localized at two sites on the second chromosome: 39DE and 42A.     

Rapid expression of novel proteins in goldfish retina following optic nerve crush

Polyadenylated messenger RNA was isolated from goldfish retinas at various times following unilateral crush of the optic nerve. RNA was translated in a cell-free system and product proteins analyzed by two-dimensional gel electrophoresis and autofluorography. Poly(A)+ mRNA-directed protein synthesis revealed an 8-fold increase in the labeling of polypeptides of about 30 kd Mr and a pI of 5.5 in retinas 2 d following optic nerve crush, compared with control retina mRNA translation products. In vitro labeling of retinal proteins revealed the enhanced synthesis of comparable 30 kd proteins in 2 d post-crush retinas. Evidence presented suggests that this 30 kd protein cluster may correspond to fish 30 kd stress or heat-shock proteins (hsp-30).     

Formation of a 22S mRNA X rRNA X protein complex during translation of globin messenger RNA

Poly(A)-rich RNA was isolated from rabbit reticulocyte polyribosomes by affinity chromatography on oligo(dT)-cellulose and fractionated in sucrose gradients under non-denaturing conditions. Most of the translatable RNA sedimented in sucrose gradients both as free 9S mRNA and as a 22S complex containing 18S ribosomal RNA and a protein of Mr 66 000. The complex was characterized by identification of the translation products. Experiments with both labelled globin mRNA and Mr-66 000 protein indicate that the complex is not an artefact, but rather that it is formed during the initiation of protein synthesis. The Mr-66 000 protein appears to be a component of the 48S pre-initiation complex and recycles before 80S complex formation.     

DNA, RNA, and protein synthesis by porcine oocyte-cumulus complexes during expansion

The experiments described in this report were designed to determine three biosynthetic functions of oocyte-cumulus complexes during expansion. The events investigated were DNA, RNA, and protein synthesis during a 24-h in vitro culture; these were determined by 3H-thymidine, 3H-uridine, and 3H-leucine incorporation into oocyte-cumulus complexes, respectively. The quality of proteins produced was also determined by slab-gel electrophoresis. Results indicated that, during follicle-stimulating hormone-induced cumulus expansion, total DNA synthesis was significantly (P less than 0.05) reduced whereas RNA synthesis remained unchanged. Overall protein synthesis was markedly increased (P less than 0.05), with one major band (Mr = 22,000) and two minor bands (Mr = 19,500 and 78,000) being produced during expansion.     

Isolation, characterization and regulation of expression of the nuclear genes for the core II and Rieske iron-sulphur proteins of the yeast ubiquinol-cytochrome c reductase

Cloning and mapping of the yeast nuclear genes for the core II (Mr 40 000) and Rieske iron-sulphur proteins of the mitochondrial ubiquinol-cytochrome c reductase, and comparison with the genomic regions in nuclear DNA from which they are derived, show that the genes are likely to be present in single copies and that they are not closely linked. They have been reintroduced into yeast cells on multi-copy plasmids and, similar to results obtained for the Mr 11 000 subunit [Van Loon et al., EMBO J. 2 (1983) 1765-1770], increase in the dosage of either gene prompts discoordinate synthesis of the encoded protein. Quantitative analysis of transformants carrying extra copies of the gene for the iron-sulphur protein shows that messenger RNA level, rate of synthesis and steady-state concentration of the protein correlate well with each other. This indicates that its level, in contrast to that of the Mr 11 000 subunit, is only determined by the concentration of its messenger RNA. Over-production of these proteins does not interfere with mitochondrial function as judged from growth rates of transformed cells on non-fermentable media. The excess Mr 40 000 protein is imported into the mitochondrion, showing that import of this subunit is not obligatorily coupled to complex assembly.     

Developmental expression of the protein product of Vg1, a localized maternal mRNA in the frog Xenopus laevis.

Vg1 is a maternal mRNA localized in the vegetal cortex of Xenopus laevis oocytes, that encodes a protein homologous to the mammalian growth factor TGF-beta. Using a polyclonal antibody to a T7-Vg1 fusion protein, we have identified the native protein. We find that a single protein of Mr 40 kd is immunoprecipitated following in vitro translation of oocyte poly(A)+ RNA, whilst two proteins of Mr 45 and 43.5 kd are immunoprecipitated from oocyte and embryo extracts. Synthesis of at least the 40 kd, in vitro, and 45 kd, in vivo, proteins is specifically inhibited following treatment of the respective systems with antisense Vg1 (but not histone H4) oligodeoxynucleotides. Tunicamycin treatment reveals the in vivo proteins to be glycosylated versions of a 40 kd protein, modified by the addition of either two or three N-linked oligosaccharide side chains. Both proteins are sensitive to digestion by the enzyme endoglycosidase-H, and are segregated within a membrane fraction from which they can be released by high pH treatment. Their synthesis is first detectable in stage IV oocytes and continues throughout early embryogenesis until the late gastrula. During embryogenesis the relative proportions of the two proteins change, the 45 kd protein being predominant in early embryogenesis and the 43.5 kd protein in late embryogenesis. Synthesis only occurs in the vegetal hemisphere at all stages; however, in the large oocyte diffusion of both proteins into the animal hemisphere occurs.     

Biosynthesis and processing of legumin-like storage proteins in Lupinus angustifolius (lupin).

Synthesis, secretion and post-translational proteolysis of the storage proteins in cotyledons of Lupinus angustifolius L. (lupin) have been examined in vivo and in vitro by using a combination of pulse-chase experiments with [3H]- or [35S]-labelled amino acids, subcellular fractionation and cell-free translation from poly(A)+ (polyadenylylated) RNA or membrane-bound polyribosomes. Related polypeptides were identified by immunoprecipitation, separation on sodium dodecyl sulphate/polyacrylamide gels and fluorography. The synthesis and processing of two proteins were compared. Conglutin alpha, the 11 S protein, was found as a family of precursor polypeptides of Mr 68000-88000 when translated from poly(A)+ RNA under conditions where signal segments were not cleaved, and Mr 64000-85000 both when sequestered into the endoplasmic reticulum and when accumulated in the protein bodies. Pulse-chase labelling showed that cotyledons from early stages of development were completely incapable of further proteolysis of these precursors. Nevertheless, in the same juvenile cotyledons, the precursors of the minor storage protein conglutin gamma, two polypeptides with Mr 50000-51000, were proteolytically cleaved to mature subunits of Mr 32000 and 17000 within 2 h. Further cleavage of the precursors of conglutin alpha into families of mature subunits of Mr 21000-24000 and 42000-62000 was detected in more mature cotyledons. A model is proposed which suggests that the mature subunits are produced by a single proteolytic cleavage of each of the three major precursors of conglutin alpha and also suggests that a close similarity exists between these subunits and those of other legumin-like proteins. The enzyme responsible for this cleavage, which appears at a specific stage in the middle of cotyledonary development, seems to be an integral part of the programmed developmental sequence in these pods.     

The surface cyclic AMP receptor in Dictyostelium. Levels of ligand-induced phosphorylation, solubilization, identification of primary transcript, and developmental regulation of expression

A monospecific polyclonal antiserum to the surface cAMP receptor of Dictyostelium has been developed by immunization with purified receptor immobilized on particles of polyacrylamide and on nitrocellulose paper. In Western blots, the antiserum displays high affinity and specificity for both the R (Mr 40,000) and D (Mr 43,000) forms of the receptor previously identified by photoaffinity labeling with 8-azido-[32P] cAMP. These bands, labeled with the photoaffinity label or with 32 Pi, were quantitatively and specifically immunoprecipitated, supporting co-purification data that all represent the same polypeptide. The R form, found in unstimulated cells, contained at least 0.2 mol of phosphate/mol of receptor. The D form, generated by cAMP stimulation of intact cells, contained at least 4 mol of phosphate/mol of receptor. In the absence of detergents, the receptor was exclusively located on membranes. The receptor was solubilized effectively in Triton X-100 and sedimented as a broad peak of 5-7 S on sucrose velocity gradients. Western blots of membranes isolated at different times after starvation indicate that the appearance of cell surface cAMP binding sites during the aggregation stage of development (5-6 h) is due to de novo synthesis of receptor protein. Pulse labeling with [35S]methionine indicated that the receptor is most rapidly synthesized during the preaggregation stage of development (1-3 h), prior to its maximal accumulation in membranes. The serum specifically immunoprecipitates a polypeptide of Mr 37,000 from an in vitro translation reaction using RNA isolated from preaggregation stage cells. The time course of expression of the mRNA coding for the Mr 37,000 polypeptide parallels the rate of receptor synthesis in vivo.     

Microsomal target proteins of metabolically activated aromatic hydrocarbons.

The specificity of binding to microsomal proteins of metabolically activated hydrocarbons has been studied. Radioactively labelled benzene, phenol, chlorobenzene, BP and MC were incubated with liver microsomes from control, phenobarbital- and MC-treated rats in the presence of an NADPH-generating system. The patterns of metabolite binding to microsomal proteins were examined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and fluorography. Benzene, phenol and chlorobenzene metabolites showed one type of binding pattern dominated by a band at 72 000 Mr. This band was strong both in control and induced microsomes. Additional radioactive bands were seen in the 50 000--60 000 Mr region particularly in MC-induced microsomes. BP and MC metabolites showed a different type of binding pattern with incorporation of radioactivity into several fractions in the 50 000--60 000 Mr region of MC-induced microsomes. Two other strongly labelled fractions occurred at 68 000 and 72 000 Mr. The incorporation was low into control and phenobarbital-induced microsomes. Two labelled bands (Mr 56 000 and 72 000) were common for all hydrocarbons in MC-induced microsomes. The 56 000 Mr band had the same mobility in the gel as an MC-induced protein likely to be cytochrome P-448. The NADPH-generating system was essential for metabolite binding and GSH and UDPGA greatly reduced binding. We suggest that differences in metabolite binding patterns reflect differences in the routes of metabolite formation and that activated hydrocarbons are likely to bind to proteins close to their site of formation.