Characterization of the protein moiety of messenger ribonucleoprotein complexes from duck reticulocytes by two-dimensional polyacrylamide gel electrophoresis

The protein moiety of duck globin messenger ribonucleoprotein complexes isolated by oligo(dT)-cellulose chromatography or by sucrose gradient centrifugation was analysed by two-dimensional polyacrylamide gel electrophoresis under conditions where the separation in the first dimension occurs according to charge and in the second according to molecular weight. By comparing the pattern of protein from the mRNA - protein complex with that of ribosomal subunits we found that two acidic proteins with an identical molecular weight of about 49 000 and three basic proteins of about Mr 56 000, 64 000 and 73 000 were associated with the duck globin mRNA but were absent from either puromycin/high-salt-derived or 'run-off' ribosomal subunits. The comparison of the proteins from the complex with mRNA with those found in the 0.5 M KCl wash, commonly used as the source of initiation factors, showed also that only the 49 000-Mr protein from the complex could possibly be present in the 0.5 M KCl wash of polyribosomes; proteins with mobilities similar to the other three proteins complexed with mRNA were not detected in the salt wash of polyribosomes.

Hemoglobin and the genetic code. Evolution of protection against somatic mutation

One-half of the twenty amino acids of the genetic code are just one mutational step away from the chain-terminator codons UAA, UAG, and UGA. It is postulated that somatic mutation to terminator is a hazard to which the organism has and to respond by adjusting certain proteins in the direction of fewer mutable residues. This view is supported by calculations based on the primary structure of five of the human hemoglobin chains. Each chain is scored for mutability to terminator in accord with the numbers and kinds of amino acids present. Among the adult chains, the most essential one, the alpha, has lowest mutability. The beta and delta follow, and in order of the presumed harm to the organism of a shortage of chain copies. Ante-natal chains tend to have higher mutabilities, supporting the view that cumulative mutational change in DNA can do little if the gene ceases to transcribe early in life. Two other predicitons based on the supposition of effective selection against mutability to terminator are also met: chain length of polypeptides is negatively correlated with their scores for mutability to terminator, and examination of the recently determined sequence of beta messenger RNA shows preferential use of codons that are not readily mutable to terminator.

Isolation of chicken hemoglobin mRNA and synthesis of complementary DNA

Chicken globin mRNA has been purified and partially characterized. Globin-specific sequences are found primarily as 9 S RNA, but also are found with ribosomal RNA, preferentially the 28 S moiety. The chicken globin mRNA preparation has been translated in the wheat germ and Krebs ascites cell-free systems. The products have been identified by sodium dodecyl sulfate-gel electrophoresis as the alpha- and beta-globin polypeptides. The globin mRNA is resolved into two asymmetric peaks by polyacrylamide gel electrophoresis in 98% formamide. The minor rapidly migrating peak consists primarily of alpha message while the major slowly migrating peak contains a mixture of alpha and beta messages. The synthesis of cDNA has been optimized and the products analyzed by polyacrylamide gel electrophoresis in 98% formamide. The products consist primarily of full copy transcripts that can be resolved into three discrete species.

Hemoglobin switching in sheep and goats. Preparation and characterization of complementary DNAs specific for the alpha-, beta-, and gamma-globin messenger RNAs of sheep

Specific complementary DNAs (cDNAs) for the messenger RNAs coding for sheep alpha-, betaA-, betaB-, betaC-, and gamma-globins were prepared by thermal denaturation of heterologous hybrids (e.g. alphabetaB-cDNA-alphagamma-mRNA) followed by hydroxylapatite chromatography. Each cDNA represented a nearly full-length copy of its globin mRNA complement as determined by electrophoretic analysis in polyacrylamide gels containing 98% formamide. The purity of each cDNA fraction was estimated by hybridization analysis and thermal denaturation. The beta- and gamma-cDNAs contained 5 to 20% contaminating alpha-cDNA while the alpha-cDNA was 25 to 30% contaminated with non-alpha-cDNA. The melting temperatures (Tm) of homologous duplexes between each non-alpha chain cDNA and its mRNA complement ranged from 69.5-71.5 degrees in 50% formamide while alpha-alpha duplexes melted with a Tm of 75-76 degrees. The Tm values of heterologous duplexes formed between each non-alpha-cDNA and the various globin mRNAs (e.g. betaB-cDNA-Hb C mRNA) ranged between 64.5 degrees and 68 degrees and thus were only 1.5-5.0degrees below that of homologous duplexes. These results suggest that the nucleotide sequence divergence among the various non-alpha-mRNAs (or cDNAs) is not greatly different from the minimum predicted from the amino acid sequence differences of the corresponding globins. When annealing reactions were performed above the Tm of the heterologous hybrids (68 degrees), each non-alpha-cDNA hybridized only to its own complementary mRNA. Thus the purified cDNAs provide molecular probes for the quantitation of alpha-, beta-, and gamma-globin-specific nucleotide sequences.

Direct demonstration of beta-globin mRNA in homozygous Ferrara betaO-thalassaemia patients

In cases of betaO-thalassaemia from Ferrara, Italy, the beta-globin gene in transcribed into mRNA but no protein is synthesised. For these cases there is no hybridisation data suggesting a globin gene structural mutation. This again demonstrates the diverse molecular events which may cause this prevalent hereditary disease.

Messenger RNA binding protein purified from reticulocyte polyribosomes

One of the proteins in the 0.5 M KCl eluate of rabbit reticulocyte polyribosomes which bind poly(A)-rich mRNA has been purified to apparent homogeneity using ammonium sulfate fractionation and phosphocellulose, hydroxylapatite, and diethylaminoethylcellulose column chromatography. The protein appears to contain two subunits of 66 700 and 56 400 apparent molecular weights with a 1:1 stoichiometry, since an apparent molecular weight of 110 000 was determined using Sephadex G-200 chromatography and an s020,w of 5.6 was obtained with rate-zonal sedimentation. The mRNA binding activity banded at pH 5.2-5.5 on isoelectric-focusing polyacrylamide gel electrophoresis. Protein-dependent binding appeared to be specific, since other natural or synthetic RNAs, including tRNA, ribosomal RNA, and poly(riboadenylic acid), were 90- to 250-fold less effective than mRNA at competing for binding of [3H]poly(adenylic acid)-rich mRNA. Poly(riboguanylic acid), however, was even more efficiently bound by this protein than mRNA.

Purification of a putative precursor of globin messenger RNA from mouse nucleated erythroid cells

Nucleated erythroid cells were incubated for 10 min in the presence of [5-3H]uridine, and the total RNA was isolated by three different extraction procedures. RNA containing globin messenger RNA sequences was purified from other cellular RNAs by selective hybridization to globin complementary DNA cellulose. Depending upon the extraction procedure employed, 0.4-0.6% of the radioactively-labeled total cellular RNA applied to the column annealed to globin complementary DNA cellulose. The annealed RNA was treated with formaldehyde and analyzed by formaldehyde/polyacrylamide gel electrophoresis. Mature globin mRNA and an RNA migrating at approximately 15 S were observed. No globin mRNA containing sequences larger than 20 S were present. The 15S RNA was partially resolved from mature globin mRNA by neutral sucrose density gradient centrifugation. The RNA isolated from the heavy region of this gradient migrated as 15 S in the formaldehyde/polyacrylamide gels and retained its ability to quantitatively anneal to globin complementary DNA cellulose. On the basis of these observations, we conclude that nucleated erythroid cells obtained from the spleens of anemic mice have a 15S RNA which contains globin mRNA sequences. The 15S RNA is not an aggregate and is a good candidate for a globin mRNA precursor.

Translation and stability of human globin mRNA in Xenopus oocytes

Human globin messenger RNA (mRNA) prepared from erythroid cells of patients with sickle cell anemia has been translated in Xenopus laevis oocytes. Addition of hemin to the injected mRNA causes total globin synthesis to increase and the ratio of alpha- to betas-globin synthesis (alpha/betas ratio) to approach unity. To determine the effect of the length of the poly-(A) segment on human globin mRNA stability, 10 S globin mRNA was fractionated into poly-(A)-poor fractions by oligo (dT)-cellulose column chromatography. When oocytes are injected with each of these fractions, translation of the poly-(A)-rich globin mRNA is sustained for a longer period than that of the poly-(A)-poor mRNA. Regardless of the mRNA fraction injected, the alpha/betas ratio of the synthesized globin decreases as the injected oocytes are incubated for longer periods. The results indicate that in frog oocytes poly-(A)-rich mRNA has greater translational stability than poly-(A)-poor mRNA, AND beta-mRNA has greater stability than alpha-mRNA with comparable poly-(A) content.

Different lifetimes of reticulocyte messenger RNA

About 85-90% of cytoplasmic protein synthesized by young reticulocytes is globin, and about 10% is a polypeptide (I) of molecular weight 64,000 daltons. Maturation of reticulocytes is accompanied by selective reduction in the synthesis of polypeptide I, relative to globin; mature reticulocytes synthesize globin at a high level but make no detectable polypeptide I. Studies in which RNA from young and old reticulocytes was translated in a wheat germ cell-free extract showed that reduction in synthesis of polypeptide I was correlated with a reduction in the amount of translatable mRNA for this protein. Differential destruction of mRNA thus is an important factor in determining the types of proteins made during the final stages of erythropoiesis.

Demonstration of non-functional beta-globin mRNA in homozygous beta (0) thalassemia

In two Chinese patients with homozygous beta(0)-thalassemia, messenger RNAs from peripheral blood reticulocytes and the bone marrow failed to direct beta-chain synthesis in vivo and in vitro in a cell-free system. Molecular hybridization showed that the beta cDNA annealed to the RNAs at almost the same rate as the alpha and gamma cDNA. The beta cDNA-RNA hydrid formed efficiently and was thermally stable, whereas hybrids between gamma and beta sequences formed slowly and denatured at a significantly lower temperature. Thus, we conclude that the beta cDNA was annealing to beta-globin sequences in these two patients, and that nonfunctional beta-globin mRNA was present. Similar results were obtained in the reticulocyte RNA from an Italian patient with homozygous beta(0)-thalassemia.

A simple method for the purification of reticulocyte globin messenger ribonucleic acid

A relatively simple and inexpensive method has been developed for the preparation of highly purified rabbit reticulocyte globin mRNA. After phenol extraction, polysomal RNA was chromatographed on Sigmacell type 38 cellulose and Sepharose 4B. The resulting mRNA preparation has a purity in excess of 90%. No selective loss of either alpha or beta globin mRNA is observed.

Changes in globin messenger RNA content during erythroid cell differentiation

Previous studies have shown that mouse fetal erythroid precursor cells isolated by an immunological technique synthesize little or no globin and contain little, if any, globin mRNA, as assayed in a cell-free system (translatable mRNA). After culture for 10 hours in the presence of erythropoietin, there is a marked increase in globin synthesis and in translatable globin mRNA. The present studies were designed to measure directly the content of globin mRNA sequences during erythroid cell differentiation, by molecular hybridization with 3H-labeled DNA complementary to globin mRNA. The results indicate that few, if any, globin mRNA sequences are present in the total RNA of erythroid precursor cells. There is little or no pool of untranslated globin mRNA in these cells. After 10 hours of culture with erythropoietin, there is an increase in globin mRNA content, as ;easured by a change in the Cot1/2 values obtained by cDNA: mRNA hybridization with (Co) representing the concentration of RNA. Between 0 and 22 hours of culture, there is a 250-fold rise, and between 22 and 44 hours, a further 2-fold increase in globin mRNA content. During the 44 hours in culture, the number of cells in culture increases 2- to 3-fold. The number of globin mRNA molecules rises in erythroid precursor cells to an average value of 1800 molecules/cell during 22 hours of culture. In cultures without added erythropoietin, the absolute number of cells decreases, however, cells presumably induced to differentiate by exposure to erythropoietin in vivo continue to differentiate in vitro, accumulating globin mRNA and initiating globin synthesis.

Potentiation of hemoglobin messenger ribonucleic acid. A step in protein synthesis initiation involving interaction of messenger with 18 S ribosomal ribonucleic acid

The polyadenylic acid-containing messenger ribonucleic acid from rabbit reticulocyte polyribosomes, isolated by a rapid and very gentle procedure (Krystosek, A., Cawthon, M. L., and Kabat, D. (1975) J. Biol. Chem. 250, 6077-6084), sediments in a sucrose gradient in three sharp peaks, at 9 S, 17 to 18 S, and 28 S. The alpha and beta globin messenger activity follows the absorbance profile in the sucrose gradients and has its major peak at 17 to 18 S. The larger messengers are more active than 9 S messenger by approximately 2-fold per mass unit of ribonucleic acid or by at least 8-fold per molecule. The major 17 to 18 S form of globin messenger was examined further and was shown to be a 1:1 complex of 9 S messenger and 18 S ribosomal ribonucleic acid. The effect of 18 S ribosomal ribonucleic acid on translation of purified 9 S globin messenger was analyzed in a messenger-dependent protein-synthesizing system (Krystosek, A., Cawthon, M. L., and Kabat, D. (1975) J. Biol. Chem. 250, 6077-6084). In the absence of exogenous ribosomal ribonucleic acid, 9 S messenger is inefficiently translated; a large excess of messenger is required to saturate the system; and globin is synthesized mainly on di- and monoribosomes. Exogenous liver or reticulocyte 18 S ribosomal ribonucleic acid potentiates 9 S messenger translation and renders it at least 10 times more efficient. The potentiation reaction can also be accomplished by increasing the concentration of ribosomes in the assay system. However, transfer or messenger ribonucleic acids cannot carry out this reaction. It is proposed that 9 S globin messenger ribonucleic acid is an inactive molecule which is normally potentiated by specific reversible base pairing with an accessible region of ribosomal ribonucleic acid contained in a 40 S ribosomal subunit. The potentiated messenger interacts with initiation factors and with other ribosomal subunits to synthesize protein. Potentiation is the first specific function in protein synthesis demonstrated for the ribosomal ribonucleic acid portion of ribosomes.

The separation of 9 S RNA from avian immature red blood cells into f2c-histone mRNA and globin mRNA

9 S RNA from avian immature red blood cells was isolated from polysome-released ribonucleoprotein particles by sucrose-gradient techniques. Translation of this RNA in an Ehrlich ascites cell-free system and product analysis revealed that globin mRNA was contaminated by f2c-histone mRNA. When 9 S RNA was applied to oligo(dT)-cellulose columns a partial separation could be achieved. Poly (A)-containing globin mRNA did not contain f2c-histon mRNA, whereas the RNA which was not absorbed to oligo(dT)-cellulose contained all the f2c-histone mRNA besides substantial amounts of globin mRNA.

Hybridization of pigeon globin messenger RNA with complementary DNA synthesized in vitro by reverse transcription: influence of the homopolymeric regions

The kinetics of hybridization of pigeon globin messenger RNA with complementary cDNA synthesized by means of AMV reverse transcriptase is complex. Addition of poly A or poly U in excess to the reaction mixture normalized the kinetics. It is concluded that association of the complementary homopolymeric regions of mRNA and cDNA accelerates the complex formation between heteropolymeric sequences in a fraction of the molecules.

Human globin gene analysis for a patient with beta-o/delta beta-thalassemia

Complementary DNA (cDNA) was prepared with RNA-dependent DNA polymerase from human globin messenger RNA (mRNA). Annealing and translation experimenta with total mRNA from circulating cells from a patient with heterozygous beta/heterozygous beta-delta-o thalassemia (beta-o/delta beta-o-thalassemia) demonstrated no detectable mRNA for beta-globin. cDNA enriched in sequences homologous to beta-globin mRNA was prepared by hydroxylapatite fractionation of hybrids formed between beta-o/delta beta-o-thalassemic mRNA and cDNA made from mRNA from a patient with alpha-thalassemia (hemoglobin H disease). The rate of annealing of this beta-enriched cDNA to normal human nuclear DNA was that of a sequence present as only a single copy per haploid genome. The beta-enriched cDNA annealed to the beta-o-delta beta-o-thalassemia total DNA with approximately the same kinetics as to normal DNA, indicating that no total gene deletion of beta-globin genes from the diploid genome has occurred, although the accuracy of the technique could not exclude with certainty a partial deletion or a deletion of a beta-globin gene from only one of the haploid genomes. This demonstrates that at least one of the beta-o- or the delta beta-o-thalassemia haploid genomes in this case contains a substantially intact beta-globin gene.

Globin mRNA translation on Artemia salina ribosomes with components from Friend leukemia cells

Globin mRNA can be translated with relatively high efficiency in a fractionated cell-free system containing ribosomes prepared from cytst of Artemia salina. These ribosomes have unusually low endogenous activity for peptide synthesis in the absence of added mRNA. The system requires components from the postribosomal supernatant and from the 0.5 M KCl ribosomal wash fraction. Both these fractions were derived from either rabbit reticulocytes or unstimulated Friend leukemia cells that produce little or no hemoglobin. The activity of mRNA and enzyme fractions from rabbit reticulocytes and Friend leukemia cells were tested in this system in vitro for their ability to direct the synthesis of the alpha and beta chains of globin. The alpha:beta chain ratio synthesized from mRNA in the rabbit reticulocyte salt wash fraction was 4:1. The corresponding value for the 9-S mRNA fraction from the salt-washed reticulocyte ribosomes was 1:4, thus these two fractions appear to provide sources enriched in either alpha or beta globin mRNA. Under all conditions tested, the ratio and amounts of peptides formed in vitro appear to reflect mRNA composition. Globin mRNA from dimethysulfoxide-stimulated Friend leukemia cells when translated in vitro produced alpha and beta chains in a ratio of 1:1. These peptides are formed in the same ratio in the intact cells.

alpha-and beta-Globin complementary deoxyribonucleic acids of human and rabbit. Specificity of hybridization

The specificity of hybridization was compared between the human and rabbit alpha and beta-globin complementary DNAs (cDNAs) and the corresponding alpha and beta-globin messenger RNAs (mRNAs). The globin chain-specific mRNAs of rabbit were prepared from polysomes incubated with O-methylthreonine (alpha and beta) or from postribosomal supernatant (alpha). Enrichment for either the alpha- or beta-globin mRNA was demonstrated by cell-free protein synthesis and by RNA-cDNA hybridization. Human mRNAs, active as templates for RNA-directed DNA polymerase, were prepared from reticulocytes of patients with hemolytic anemia, alpha-thalassemia (hemoglobin H disease), and beta-thalassemia. Because there was partial cross-hybridization between human mRNA and rabbit cDNA, the rabbit alpha- and beta-globin cDNAs could be used to demonstrate that the beta-thalassemia mRNA was enriched in human alpha-globin mRNA sequences and that the alpha-thalassemia mRNA was enriched in human beta-globin mRNA sequences. These results were confirmed by preparation of thalassemia globin cDNAs and subsequent hybridization to their template mRNAs. The amount of cross-hybridization between the human and rabbit alpha-globin mRNA and the two alpha-globin cDNAs was comparable to the cross-hybridization between the two beta-globin mRNAs and the two beta-globin cDNAs, indicating a similar degree of evolutionary divergence in the nucleotide sequences of the two globin genes.

Further evidence of a quantitative deficiency of chain-specific globin mRNA in the thalassemia syndromes

Formamide gel electrophoresis separates the mRNA fraction from reticulocyte polyribosomes of adult humans into two major RNA species with migratory rates identical to those of the alpha- and beta-globin mRNAs of the rabbit. That these two RNAs of human origin are the globin mRNAs is further supported by the deficiency of the presumed beta mRNA in reticulocyte polyribosomes of fetuses and premature infants, whose cells make gamma chains in preference to beta chains. The globin mRNAs of reticulocyte polyribosomes from patients with hematological disorders were estimated by scanning the stained formamide gels. In contrast to individuals with either hemolytic anemia without hemoglobinopathy or sickle cell anemia who had beta mRNA to alpha mRNA ratios of approximately one, a patient with Hb S-beta-thalassemia had a ratio of beta mRNA to alpha mRNA of 0.75 while two subjects with homozygous beta-thalassemia had severe deficiencies of beta mRNA. Conversely, a patient with alpha-thalassemia (Hb H disease) had a ratio of beta mRNA to alpha mRNA on reticulocyte polyribosomes of 6. These data provide further evidence of a quantitative deficiency of chain-specific globin mRNA in patients with the thalassemia syndromes.

Synthesis of alpha- and beta-globin directed by messenger ribonucleoprotein from rabbit reticulocytes

The translation of globin messenger ribonucleoprotein (mRNP) obtained from high salt-washed rabbit reticulocyte ribosomes by treatment with EDTA was investigated using a cell-free system from mouse Krebs II ascites tumour cells. The messenger activity of the mRNP and the mRNA derived from it by mild deproteinization was compared in the presence and absence of reticulocyte initiation factors. Both forms gave identical products over a wide range of messenger concentration and there was no qualitative or quantitative difference in their efficiency as messengers. It is concluded that the proteins associated with polysomal mRNA do not alter the specificity of translation of alpha- and beta-globin messengers or the requirement for initiation factor.

Evidence for multiple forms and partial resolution of rabbit reticulocyte alpha- and beta-globin messenger RNA by gel isoelectric focusing

Isoelectric focusing in polyacrylamide gels has been used to fractionate and characterize RNAs from rabbit reticulocytes with major emphasis on globin mRNA. Reticulocyte 18S and 28S RNAs banded essentially as single components, well separated from each other and from the multiple forms of tRNA. By contrast, mRNA was resolved into a number of major and minor components. These bands were shown to contain intact globin mRNA by translation in a messenger-dependent cell-free protein synthesizing system. One major band was enriched slightly in alpha-globin mRNA and a second major band was enriched considerably in beta-globin mRNA. Reticulocyte supernatant mRNA, containing predominantly alpha-globin messenger, demonstrated only one major component which banded at the same position as the alpha-enriched band from total mRNA. Little of this material behaved as beta mRNA either by its focusing profile or by its translation products. Globin mRNA fractions with high and low 3' poly(A) contents also demonstrated differences in focusing distribution profiles. Although the basis for separating RNA by this technique has not been established, our results suggest that isoelectric focusing may offer a new approach to fractionation and characterization of specific mRNA species.

Globin mRNA from rabbit reticulocyte membrane-bound ribosomes

Messenger RNA has been isolated from both free and membrane-bound rabbit reticulocyte ribosomes. Membrane-bound ribosomes, which constitute less than 10% of total cellular ribosomes, are released from the membrane by deoxycholate but remain associated with the membrane fraction following treatment with 0.5 M KC1. The major messenger RNA species isolated from either free or bound ribosomes is globin messenger. Both alpha- and beta-globin chains are synthesized when the isolated messenger RNA from either free or membrane-bound reticulocyte ribosomes is added to a Krebs ascites cell-free system.

Cell-free translation of the globin message within polydisperse high-molecular-weight ribonucleic acid of avian erythrocytes

Polydisperse high-molecular-weight RNA of nucleated avian erythrocytes includes sequences coding for globin chains. The RNA was extracted from immature erythrocytes of ducks and fractionated under denaturing conditions by sucrose density gradient centrifugation in 99% dimethylsulfoxide. The RNA sedimenting faster than 45 S was able to direct the synthesis of duck globins in the Krebs II ascites cell-free protein-synthesizing system. The newly synthesized globin molecules have been identified by their characteristic electrophoretic properties in polyacrylamide gels containing either urea or sodium dodecyl sulfate, and by immunoprecipitation of the released globin chains by rabbit antibodies against duck hemoglobin. In order to rule out the possibility of a contamination of the high-molecular-weight RNA with duck-globin messenger RNA tailing from the 9-10S region, rabbit-globin messenger RNA was added to duck RNA as an internal control. No rabbit-globin messenger RNA activity could be detected in the RNA fractions sedimenting faster than 45 S. It is concluded that high-molecular-weight RNAs in the nucleated erythroid cell contain sequences of globin messenger RNAs covalently attached to larger polynucleotide chains. These results support the view that polydisperse nuclear RNA is the precursor of the cytoplasmic messenger RNA fraction.

Decreased globin messenger RNA in thalassemia detected by molecular hybridization

In previous studies of patients with beta thalassemia, mRNA extracted from reticulocytes in peripheral blood when added to cell-free systems reproduces the deficient beta-chain synthesis characteristic of intact cells. The present studies with specific probes for alpha and beta mRNA were designed to decide whether the decreased beta mRNA activity is due to the presence of abnormal or reduced beta globin mRNA in these cells. Purified alpha and beta complementary DNAs (cDNAs) have been synthesized with RNA-instructed DNA polymerase; alpha and beta mRNAs isolated from heavy (beta-producing) and light (alpha-producing) polyribosomes of rabbit reticulocytes were used as templates. Each of the cDNAs is more than 80% pure by the criterion of biological activity. The alpha cDNA labeled with [(32)P]dCTP and the beta cDNA labeled with [(3)H]dCTP have been added simultaneously to reaction mixtures containing various concentrations of mRNA from thalassemic and nonthalassemic subjects. The extent and rate of hybridization were determined, permitting a comparison of relative alpha and beta mRNA content in the same annealing mixture. In six nonthalassemic patients, relatively equal amounts of hybridizable alpha and beta mRNA appear to be present. In five of seven patients with beta-thalassemia, significantly decreased amounts of beta mRNA compared to alpha mRNA can be demonstrated. In two patients with Hemoglobin H disease, there is a decreased amount of alpha mRNA compared to beta mRNA.

Monoribosomal attachment to messenger ribonucleic acid in sodium fluoride-treated rabbit reticulocytes

Mild proteolysis with Pronase selectively dissociates ribosomes not attached to mRNA into subunits; ribosomes attached to mRNA remain intact. A portion of monoribosomes from reticulocytes incubated with NaF resisted proteolytic dissociation. Recovery of mRNA from monoribosomes of NaF-treated reticulocytes therefore may be explained by persistent attachment of some monoribosomes to mRNA.