Translation of two messenger RNAs from lens in a cell free system from Krebs II ascites cells

Comparison of the crystallin mRNA populations from rat, calf and duck lens. Evidence for a longer alpha A2-mRNA and two distinct alpha B2-mRNAs in the birds

Total cytoplasmic poly(A)-containing RNA from rat, calf and duck lens was fractionated by electrophoresis in methylmercury hydroxide-containing agarose gels. RNA electrophoresed in parallel lanes was either transferred onto nitrocellulose and hybridized with total cDNA synthesized on the initial mRNA or was recovered from individual gel fractions for in vitro translation in a reticulocyte cell-free system. This allowed the identification and size-characterization of individual mRNA species encoding alpha-, beta-, gamma- and delta-crystallin polypeptides. The 14 S mRNA fraction of rat lens comprises two alpha A2-mRNAs of approximately 1250 and 1350 nucleotides and the alpha AIns-mRNA with a size similar to that of the largest alpha A2-mRNA. The calf lens 14 S mRNA fraction harbors a heterogeneous population of alpha A2-mRNA. In the same fraction another mRNA encoding a polypeptide, designated X, has been found sharing no homology with alpha A sequences. The duck lens alpha A2-mRNA appears to be 400-450 bases longer than the rat and calf lens alpha A2-mRNAs. Furthermore, in contrast to the single alpha B2-mRNA in rat and calf lens, two alpha B2-mRNAs have been identified in duck lens, one, the major species, similar in size to the alpha B2-mRNA in rat and calf lens (800 bases), and the other species 700 nucleotides longer. The large size differences among the alpha A2- and alpha B2-mRNAs most likely reside in their 3'-untranslated sequences.

Ontogeny and localization of the alpha-, beta-, and delta- crystallin antigens during lens development in mallard embryos

The ontogeny of alpha-, beta-, and delta-crystallin antigens in the developing lens of mallard (Anas platyrhynchos) was investigated by indirect immunofluorescence using specific antibodies to mallard alpha-, beta-, and delta- crystallins raised in rabbits. The IgG fraction from each antiserum was isolated by affinity chromatography usign Protein A Sepharose CL-4B. Fluoresceinee (FITC) or rhodamine (TRITC) conjugated goat anti rabbit (GAR) gamma-globulin was used as the secondary antibody. The results show that alpha-, beta-, and delta-crystallins appear simultaneously in the developing mallard lens and are detectable from 66 hr (stage 15/16). This situation is different from the chick where delta- is known to appear first followed by beta-, and alpha-. This could be due to species variation. In the epithelium, however, as in the chick, delta- emerges first followed by beta-, and alpha- but rather late when compared with the chick and this seems probably due to a difference in the incubation time between the two species. Results from immunofluorescence and Tris-SDS gel electrophoresis demonstrate that alpha A subunit of the alpha-crystallin appears much earlier than the alpha B subunit. We also found that the newly discovered epsilon-crystallin (18) appears long after the three major crystallin classes.

Post-translational assembly of lens alpha-crystallin in the reticulocyte lysate and in Xenopus laevis oocytes

Lens mRNA was translated in reticulocyte lysate predominantly into monomeric alpha-crystallin chains. Lens polyribosomes added to the cell-free system produced the same polypeptides, but these were detected predominantly in alpha-crystallin aggregates. Lens mRNA, after microinjection into Xenopus laevis oocytes, produced alpha-crystallin subunits that were exclusively found in the form of high-molecular-weight complexes. Also after injection of the purified 14-S mRNA, coding for the alphaA subuint, the synthesized alpha-A polypeptides were incorporated into high-molecular-weight aggregates. In contrast, the synthesis of alphaB subunits, directed by a 10-S mRNA, did not result in aggregate formation. The experiments thus suggest that aggregate formation of alpha-crystallin is triggered by its alphaA subunits, which are then joined by the alphaB subunits. This process occurs partly in the cell-free system and completely in Xenopus oocytes.

Inhibition of translation of lens mRNAs in a messenger dependent reticulocyte lysate by cap analogues

The nuclease treated reticulocyte lysate forms a highly efficient and completely mRNA-dependent cell-free system. In this system the functioning of the cap on eukaryotic mRNAs was explored by blocking cap recognition with cap analogues. Translation of capped mRNAs was severely inhibited, while translation of uncapped mRNAs was unaffected. It is concluded that this cell-free system can be used for screening cap dependence in the translation of specific mRNAs, like calf lens mRNAs. At 1.2 mM m7G5'p, 0.16 mM m7G5'pp or 0.16 m7G5'ppp5'G, translation of all lens mRNAs was totally inhibited. At lower concentrations the sensitivity to cap analogues was different for the various species of lens crystallin messenger. gamma-Crystallin mRNA showed relatively the lowest response. The translation of added polyribosomes was also inhibited by the cap analogue. It is concluded that translation of all crystallin messengers is cap-dependent.

In-vitro translation of messenger-RNA from developing bean leaves. Evidence for the existence of stored messenger-RNA and its light-induced mobilisation into polyribosomes

Poly(A)-containing messenger RNA was purified from polyribosomes isolated from the primary leaves of 7-day-old dark-grown seedlings of Phaseolus vulgaris var. Masterpiece. Analysis of the messenger RNA on 2.4% polyacrylamide gels showed that it consists of a heterogeneous population of molecules with an average molecular weight of 500,000. The nucleotide composition of the RNA was 16.0% cytidylic acid, 39.4% adenylic acid, 21.3% guanylic acid and 23.2% uridylic acid. Based on the degree of resistance of the RNA to digestion with ribonucleases A and T1 the average length of the poly(A) sequence was calculated to be 120 nucleotides. No significant differences in mobility in polyacrylamide gels, nucleotide composition or polyadenylic acid content were found between the poly(A)-containing mRNA from polyribosomes of primary leaves of dark-grown plants and those given a 16 h white light treatment. Purified poly(A)-containing mRNA was shown to direct the incorporation of [(35)S]methionine into proteins in an in vitro protein-synthesising system from wheat germ. The protein products were fractionated according to molecular size by electrophoresis in 15% polyacrylamide/urea/SDS gels and the protein bands were detected by fluorography. Messenger RNAs directing the synthesis of three polypeptides with molecular weights of 34,000, 32,000 and 25,000 were detected in polyribosomes of plants following white light treatment. These messenger RNAs were absent, or present in much lower amounts, in polyribosomal messenger RNA from leaves of dark-grown plants, although they were present in total cell poly(A)-containing RNA. This indicates that certain messenger RNAs may be stored in the dark and that light stimulates these RNAs to engage in polyribosome formation. Continuous far-red (730 nm) irradiation for 4 h also caused the appearance of these messenger RNAs in the polyribosomes although 5 min red light followed by 4 h darkness had little effect. This suggests that phytochrome acting in the "high energy" mode, may be the photoreceptor responsible for initiating the response.

Translation of mRNA from rat-liver polysomes into tyrosine aminotransferase and tryptophan oxygenase in a protein-synthesizing system from wheat germ. Effects of cortisol on the translatable levels of mRNA for these two enzymes

Messenger RNA was isolated from rat liver polysomes by phenol/chloroform extraction and subsequent oligo(dT)-cellulose chromatography. The mRNA was translated in a protein-synthesizing system in vitro derived from wheat germ. The system was optimized in respect to Mg2+ and K+. The presence of spermidine or spermine is necessary for the synthesis of polypeptides having molecular weights of over 20 000. In the absence of the bases only small molecular weight products are formed. The amount of protein synthesized is linearly dependent on the amount of mRNA added up to concentrations of 80 mug mRNA/ml. The synthesis of tyrosine aminotransferase and tryptophan oxygenase in the system in vitro has been demonstrated by specific immunoprecipitation and sodium-dodecylsulfate polyacrylamide gel electrophoresis of the precipitate with enzyme proteins as marker. The amount of specific product formed is linearly dependent on the amount of mRNA present. The amount of translatable tyrosine aminotransferase mRNA and tryptophan oxygenase mRNA increases after administration of hydrocortisone to adrenalectomized rats. At low doses of hormone (2 mg/100 g body weight) maximal values are observed at 4 h, control levels being reached at 6-8 h after hormone application. With higher doses of hydrocortisone (20 mg/100 g body weight) maximal values are attained at 6 h, tending to control levels 14 h after treatment. The enzyme activity curves are parallel to the mRNA curves, the peak of enzyme activity occurring 2 h after the peak of mRNA activity.

Messenger RNA translation in the presence of homologous and heterologous tRNA

The effect of tRNA distribution in the cell on the rate of specific protein synthesis has been investigated. A tRNA-dependent cell-free protein-synthesizing system derived from Krebs-II ascites cells has been worked out. In this system it is possible to synthesize specific proteins (egg-white proteins or globin) by the translation of oviduct or reticulocyte messenger RNA in the presence of tRNA from homologous or heterologous tissues. The rate of translation of a give messenger RNA is optimal in the presence of tRNA from the homologous tissue. The lower level of protein synthesis obtained with an excess of heterologous tRNA can be overcome by adding the homologous tRNA. Nevertheless homologous isoaccepting species partly purified by a reversed-phase chromatography or a benzoylated DEAE-cellulose column cannot fully restore the optimal synthesis, eliminating the hypothesis according to which a particular tRNA species is involved in this phenomenon. The correct distribution of tRNA is necessary for optimal translation of a messenger RNA.

Immunochemical isolation and characterization of vitellogenin mRNA from liver of estradiol-treated chicks

Vitellogenin mRNA was purified through three steps. A heavy polysome fraction was obtained by discontinuous sucrose density gradient centrifugation, vitellogenin polysomes were immunoprecipitated with affinity-chromatography-purified anti-lipovitellin IgG and goat anti-rabbit IgG, the enriched mRNA was isolated on a poly(U)-Sepharose column. As judged by its specific activity in a reticulocyte lysate system, vitellogenin mRNA has been enriched a 1000-fold with a recovery of 30%. On 99% formamide 3.4% polyacrylamide gels vitellogenin mRNA has an Mr of 2.4-2.5 X 10(6) and codes for a peptide of Mr 240000, which under our incubation conditions is partially degraded to smaller peptides.

Calf lens messenger ribonucleoprotein complexes. Characterization and comparison of template activity with corresponding mRNAs

Lens messenger ribonucleoprotein complexes have been isolated from calf lens polysomes by sucrose gradient centrifugation after puromycin-induced dissociation. A 10 S mRNA was released from a 13 S messenger ribonucleoprotein complex and a 14 S mRNA from a 19 S messenger ribonucleoprotein complex. Two major protein components with molecular weights of approx. 64 000 and 40 000 were isolated from each of the messenger ribonucleoprotein complexes after RNAase digestion. Buoyant density determinations suggest that the messenger ribonucleoprotein complexes contain approximately one mol of each major protein species per mol mRNA. In contrast to lens mRNA, lens messenger ribonucleoproteins are poor templates for transcription with avian myeloblastosis virus reverse transcriptase. Similar results were also obtained with globin messenger ribonucleoprotein containing either two major protein species (or deficient in the lower molecular weight protein species). Polynucleotide phosphorylase eliminates the reverse transcription template activity of the lens mRNA. This effect is blocked in the messenger ribonucleoprotein. Such observations suggest that at least one of the protein components associated with lens messenger ribonucleoprotein may be located in the 3'-terminal region. Only a small variation in translation activity was observed between the messenger ribonucleoproteins and their respective mRNAs.

Further studies on the lens cell-free system. In vitro synthesis of the non-crystallin lens proteins

1. The lens cell-free system synthesizes in addition to the crystallins, polypeptides which co-electrophorese with lens plasma membrane protein components. 2. Isolated lens polysomes can be translated in a heterologous cell-free system. They code for both the crystallins and membrane-protein-like components. 3. If messengers isolated from these polysomes by affinity chromatography on oligo-(dT)-cellulose are added to a heterologous cell-free system, only lens proteins of lower molecular weight are synthesized. 4. Different ionic conditions are required for optimal translation of different lens messengers.

A transfer RNA-dependent protein synthesizing system from Ehrlich ascites extracts

An homologous cell-free system from Ehrlich ascites cells was made tRNA dependent by passing both the ribosomes and the ammonium sulfate fraction through DEAE-cellulose columns in 0.30 M KCl. Protein synthesis was routinely stimulated 20-50 fold by the addition of 100 mug/ml of ascites cell tRNA in the presence of oviduct mRNA, ascites mRNA, or encephalomyocarditis RNA.

Translation of poly(riboadenylic acid)-enriched messenger RNAs from the yeast, Saccharomyces cerevisiae, in heterologous cell-free systems

Poly(riboadenylic acid) [poly(A)] enriched messenger RNAs from yeast have been used to direct the synthesis of yeast polypeptides in mouse Krebs II ascites and wheat embryo extracts. Both cell-free systems, synthesize polypeptides over a molecular weight range of 10,000-100,000. Autoradiograms of sodium dodecyl sulfate-polyacrylamide slab gels used to fractionate [35S]methionine-labeled in vitro products reveal that about 25 major bands (each of them possibly representing multiple polypeptides) are produced by each cell-free system. Each of these coelectrophoreses with a major polypeptide labeled in vivo or in a yeast lysate. These results suggest that cell-free translational machinery from eukaryotes is not able to discriminate in an all or none fashion against messenger RNAs which are available to it. While yeast poly(A)-enriched messenger RNA directs the synthesis polypeptides over approximately the same molecular weight range in both cell-free systems, the wheat germ system directs the incorporation of 45 times the amount of [3H]serine into Cl3CCOOH-precipitable polypeptides. This is in contrast to the 2.5-fold more efficient translation of hemoglobin mRNA in the wheat embryo extract. Thus, the extract from mammalian cells is able to translate mRNA from a lower plant with a much lower efficiency than it translates hemoglobin mRNA, and at a lower efficiency than is observed using a cell-free system from wheat embryos. This indicates that the wheat embryo system is the one of choice for translation of yeast messenger RNA.

The cell-free translation of Rauscher leukemia virus RNA into high molecular weight polypeptides

Rauscher leukemia virus (RLV) 65-S RNA, 35-S mengovirus RNA and reticulocyte A-rich RNA each stimulated cell-free protein synthesis in a JLS-V5 cell derived S-30 system. rRNA, however, was not stimulatory in this system. Of the stimulated protein products only those synthesized in response to added RLV RNA were immune-precipitable with anti-RLV rabbit serum. Furthermore, cell-free incubations with pactamycin at a concentration which specifically inhibits initiation and not elongation prevented the stimulation of amino acid incorporation in response to added RLV RNA. Analysis of the polypeptides synthesized by the cell-free system in response to reticulocyte A-rich RNA, showed them to be globin-like and, therefore, also mRNA specific. The RLV RNA-directed product included at least two classes of polypeptides (mol. wts of 140 000-185 000 and 50 000-75 000) both of which were larger than the group specific polypeptides of mature virions. None of the internal structural polypeptides of mature virions were synthesized in response to RLV RNA. The large molecular weight, viral-specific polypeptides are candidate precursor polyproteins which may represent the translational products of a polycistronic mRNA with a single initiation site.

Individual histone messenger RNAs: identification by template activity

Newly synthesized polysomal messenger RNAs from cleavage stage embryos of the sea urchin Arbacia punctulata and Lytechinus pictus that contain putative histone mRNAs have been fractionated on 6% polyacrylamide slab gels. At least 8 RNA species with unique electrophoretic mobilities have been recognized. The complex of RNAs has been eluted from the gels in three groups, A, B, and C, in increasing order of mobility. The template activity of the three fractions and the unfractionated starting material was examined in the mouse Krebs II ascites tumor cell-free protein synthesizing system. The unfractionated messenger complex programs the synthesis of proteins that co-electrophorese exclusively with sea urchin histones in both sodium dodecyl sulfate and acid urea gel systems. The products of in vitro protein systhesis stimulated by the individual polyacrylamide gel RNA fractions were similarly examined. Each stimulated protein synthesis and was enriched for specific histone templates. We conclude that RNA fraction A is template for histone f1, C is template for histone f2a1, and B serves as template for f2b, f2a2, and f3 histones. A minor degree of contamination of the A and B RNA fractions was obvious from the production of other histones by each template. The co-electrophoresis of specific template activity with specific radiolabeled RNAs supports the concept that most or all of the labeled RNAs are indeed themselves the histone mRNAs.

Translation of mRNA for 3,4-dihydroxyphenylalanine decarboxylase isolated from epidermis tissue of Calliphora vicina R. -D. in a heterologous system. Dependence of mRNA concentration on the insect steroid hormone ecdysone

RNA was isolated from the epidermis of Calliphora vicina larvae by phenol--chloroform extraction. The RN A sedimenting in sucrose gradients between 5 and 18 S was submitted to chromatography on oligo(dT)-cellulose columns. The fraction binding to the oligo(dT) is able to stimulate protein synthesis in a system consisting of mouse liverribosomal subunits, pH-5 factors from rat liver and initiation factors from rabbit reticulocytes. Optimal Mg2+ concentration for the translation of insect mRNA is 3.5 mM, that of K+ 76 MM. Initiation factors prepared from epidermis of Calliphora larvae are less efficient in the translation of insect mRNA than initiation factors isolated from reticulocytes. The pH-5 fraction from epidermis inhibits protein synthesis independent of the source of the mRNA fraction used. One of the proteins synthesized in the reconstituted system under the direction of insect mRNA has been identified as 3,4-dihydroxyphenylalanine (DOPA) decarboxylase by immunoprecipitation with specific antiserum against DOPA decarboxylase and comigration in dodecylsulphate-acrylamide electrophoresis with pure DOPA decarboxylase. Both mRNA from white prepupae and from 6--7-days-old larvae contain sequences coding for DOPA decarboxylase. However, white prepupae contains 3--4 times more DOPA decarboxylase-mRNA than 6--7-days-old larvae. The content of DOPA decarboxylase mRNA is proportional to the amount of active DOPA decarboxylase molecules present in the animals from which the mRNA was isolated.

Effect of development on the translation of messenger RNA in Artemia salina embryos

Cell-free preparations from encapsulated Artemia salina embryos readily translate poly(U), but there is no endogenous protein synthesis or translation of added natural mRNA until development resumes upon incubation in saline. High-salt-washed 80S ribosomes and highspeed supernatant (cytosol) were prepared from undeveloped eggs and from eggs allowed to develop to a stage prior to hatching. Endogenous protein synthesis occurs only with ribosomes from developed embryos, whether with undeveloped or developed cytosol. This is mainly elongation of preformed polypeptide chains, for it is largely resistant to edeine, an inhibitor of chain initiation. Edeinesensitive translation of added natural mRNA occurs with both developed and undeveloped ribosomes but requires developed cytosol. Translation of brome mosaic virus RNA is not much, if at all, further stimulated by high-saltwash of developed ribosomes, but that of globin mRNA is markedly enhanced. Levels of the chain initiation factor EIF-1 are the same before and after development. These results are consistent with the view that resumption of developemtn is triggered by transcription, with ensuing translation of the resulting messengers to yield, among other proteins, mRNA-recognizing initiation factors of the IF-3 type which are partly free in the cytosol and partly ribosome-bound. The data also suggest that different factors may be involved in the translation of brome mosaic virus RNA and globin mRNA by this system.

Cell-free synthesis of adenovirus 2 proteins programmed by fractionated messenger RNA: a comparison of polypeptide products and messenger RNA lengths

Cytoplasmic RNA extracted from human tissue culture cells infected with adenovirus type 2 was used to program protein synthesis in a cell-free system derived from mammalian cells. Analysis of the protein product by polyacrylamide gel electrophoresis revealed ten adenovirus-specific polypeptides. Five of these were further identified by analysis of tryptic peptides. Translation of RNA fractionated by sedimentation through sucrose gradients containing formamide demonstrated seven size classes of RNA, each of which programmed the synthesis of only one or two virus-specific polypeptides. Six of the virus-specific polypeptides were translated from RNAs much larger than expected for the size of the polypeptide.

Isolation and in vitro translation of delta-crystallin mRNA from embryonic chick lens fibers

Of the protein synthesized and accumulated during differentiation of embryonic chick lens fibers, 70-80% is the tissue specific protein delta-crystallin. We have isolated and partially characterized the total cytoplasmic mRNA from purified lens fibers of 15-day-old embryos as an initial step toward understanding the regulated expression of delta-crystallin during development. Each lens fiber mass contained an average of 10 mug of cytoplasmic RNA; approximately 0.1 mug per fiber mass was recovered in the mRNA fraction by oligo(dT)-cellulose chromatography. The mRNA electrophoresed primarily as a single peak on a polyacrylamide-agarose gel with an apparent molecular weight of about 9 x 10(5) estimated by comparison with 28S and 18S rRNA markers. Of the protein synthesized in response to the mRNA in cell-free systems derived from Krebs II ascites tumor cells or rabbit reticulocytes, 70-80% comigrated with delta-crystallin on sodium dodecyl sulfatepolyacrylamide-agarose gels. Comparison of the tryptic peptides of delta-crystallin with those of the in vitro products from both heterologous systems established that the lens fiber mRNA contained delta-crystallin mRNA, and that no other functional mRNAs were present in detectable quantities. Thus, the specialization of protein synthesis in embryonic chick lens fibers apparently results from an accumulation of delta-crystallin mRNA in the cytoplasm.

Characterization of ribonucleic acids from the venom glands of Crotalus durissus terrifucus (Ophidia, Reptilia) after manual extraction of the venom. Studies on template activity and base composition

RNA synthesis in the venom glands of Crotalus durissus terrificus was stimulated by the manual extraction of the venom (milking). RNA was extracted from venom glands activated by milking and fractionated by centrifugation through sucrose density gradients. Template activity for protein synthesis and base composition of the RNA fractions were studied. RNA fractions that sediment between 18S and 4S had the highest template activity. The base composition analysis indicated that the 28S and 18S rRNA have a C+G content of 65.4 and 58% respectively. The ;melting' temperature (T(m)) of DNA in 0.15m-NaCl-0.015m-trisodium citrate, pH7.0, was 85 degrees C, corresponding to a C+G content of 38%. The base ratio of the RNA fractions that showed a high template activity was intermediate between that of rRNA and homologous DNA. The possible role of these fractions in the synthesis of the two main toxins (crotoxin and crotamine) of the South American rattlesnake's venom is discussed.

Calf lens crystallin messenger RNA's contain polynucleotide sequences rich in adenylic acid

Calf lens messenger fractions have been purified on poly(dT)-cellulose. The purified RNA's have been analyzed as nucleosides by a method which can be used on a micro-scale with highly reproduceble results. Both the 10S and 14S lens mRNA contain poly A sequences. The poly A content found in 14S mRNA cannot account for the excess nucleotides in this message.

Cell-free synthesis of rat growth hormone

Growth hormone has been synthesized in a cell-free system derived from Krebs II ascites cells, under the direction of RNA prepared from rat pituitary tumor (GC) cells. Growth hormone synthesized in the cell-free system was identified by precipitation with antiserum against growth hormone developed in baboon, followed by electrophoretic analysis of the dissolved precipitate on sodium dodecyl sulfate-polyacrylamide gels. RNA from both the membrane and the post-membrane fractions of the cytoplasm of GC cells stimulated protein synthesis in the cell-free system, but only RNA from the membrane fraction was found to direct the synthesis of growth hormone.

In vitro translation of oogenetic messenger RNA of sea urchin eggs and picornavirus RNA with a cell-free system from sarcoma 180

A cell-free protein-synthesizing system prepared from mouse sarcoma 180 was characterized by use of RNA from mengo virus and sea urchin egg. In the presence of exogenous mammalian transfer RNA, total sea urchin egg RNA and mengo RNA direct incorporation of [(3)H]leucine into acid-insoluble material. The system is extremely efficient in that a stimulation of 100-times over background can be obtained. Studies with formylmethionyl-transfer RNA, as well as with inhibitors of initiation, indicate that multiple initiation occurs; further, 85-90% of all chains made in vitro are subsequently released from ribosomes. An average translation time of 3.5 min was determined with messenger RNA of sea urchin egg, and product analysis indicates that high-molecular-weight products (greater than 50,000 molecular weight) are being made in vitro. Sequences of sea urchin egg RNA containing poly(A) act as messenger RNA.