The RNA conformational requirements for both aminoacylation and adenylation emerging from our studies performed using the valine- and the tyrosine-accepting plant viral RNAs are now strongly supported by the histidine-accepting tobacco mosaic virus RNA: an 'L'-shaped conformation is recognized by the aminoacyl-tRNA synthetase whereas only the aminoacyl RNA domain (equivalent in tRNAs to the continuous helix formed by the acceptor stem and the T stem and loop) interacts with the tRNA nucleotidyltransferase.

The proteins synthesized under the direction of alfalfa mosaic virus RNAS in tobacco leaves have been examined under conditions of suppressed host protein synthesis. Besides the coat protein we could detect a 22K (K = apparent molecular weight in thousands), a 35K, and a set of 54K proteins. The 22K protein is serologically related to the coat protein. The 35K protein comigrated with the 35K protein whose synthesis is directed by RNA 3 in vitro The 54K proteins are serologically related to the 35K protein produced in vitro. Readthrough products of the 35K protein cistron into the coat protein cistron have been found previously in wheat germ extracts programmed with RNA 3. Two of these proteins comigrate with the 54K proteins synthesized in vivo. Since the 35K and the coat protein cistrons are read in different reading frames the formation of readthrough products is puzzling. In viruses with a tripartite genome the subgenomic mRNA for coat protein, RNA 4, is not known to be replicated as a separate genome entity. This might indicate that proteins synthesized by readthrough into the coat protein cistron play an essential role during replication, especially in the earliest phases.

Turnip yellow mosaic virus (TYMV) Val-RNA forms a complex with the peptide elongation factor Tu (EF-Tu) in the presence of GTP: the Val-RNA is protected by EF-Tu.GTP from non-enzymatic deacylation and nuclease digestion. The determination of the length of the shortest TYMV Val-RNA fragment that binds EF-Tu.GTP leads us to conclude that the valylated aminoacyl RNA domain equivalent in tRNAs to the continuous helix formed by the acceptor stem and the T arm is sufficient for complex formation. Since the aminoacyl RNA domain is also sufficient for adenylation by the ATP(CTP):tRNA nucleotidyltransferase, an analogy can be drawn between these two tRNA-specific proteins.

The existence of subgenomic RNAs is well established in the case of plant viruses such as tobacco mosaic virus (TMV). However, except for the subgenomic coat protein mRNA, it is not known whether the other subgenomic RNAs have a function in the life cycle of the virus. In search of more information about one of the major subgenomic RNAs-intermediate length RNA-2 or I2 RNA-of TMV, in vitro and in vivo translational studies were performed. The I2 RNA, which codes in vitro for the synthesis of a 30K (K = kilodalton) protein, appears to be uncapped as judged by the need of different in vitro translation conditions for the synthesis of this protein, compared to the conditions required for the synthesis of the 126K and 183K proteins coded by the capped genomic RNA. In vivo a protein migrating in the same position as the 30K protein synthesized in vitro can be detected in infected tobacco leaves. Since this protein occurs transiently early upon infection, whether it is virus-coded or virus-induced, it could have an early function during infection.

VIROLOGY 127, 235 (1983) Author Index for Volume 127, Number 1 ADAMS, MICHAEL K., 168 ANDBRSON, CARL W., 112 ATABEKOV, J. G-, l G GARDES, MARYVONNE, 74 GAY, MARY, 88 GUSTAFSON, G. D-, 37 0 OHNO, TAKESHI, 54 OKADA, YOSHIMI, 54 BAGLIONI, CORRADO, 225 BASERGA, RENATO, 149 BEATY, BARRY J., 83 BELZHELARSKAYA, SN, l BEN-PORAT, TAMAR, 194 BERNARDS, REN 45 BILIMORIA, SL, 15 BISHOP, DAVID HL, 83, 205 Bos, JOHANNES L., 45 BOSCH, L., 100 BRITT, W., 134 C CHAPEVILLE, F., 100 CHESEBRO, B., 134 CLERX, JOHN PM, 205 CLOYD, M., 134 COLLMER, CANDACE WHITMER, 230 COVEY, SN, 37 CROCE, CARLO M., 149 DA VIES, JW, 37 DAWSON, JR 0., 37 DOUA, VV, l EVANS, L-, 134 FALTYNEK, CONNIE R., 225 FEUNTEUN, JEAN, 74 FIELDS, BERNARD N., 220 FUJISAWA, HISAO, 124 FULLER, FREDERICK, 83, 205 HAENNI, AL, 100 HULL, R …

Bromo‐ and cucumovirus RNAs contain a tRNA‐like structure as an integral part of their genome. This structure is located at the 3′ end of the viral RNA and is an acceptor of tyrosine. The 3′ regions of representative viral RNAs have been sequenced and quite unorthodox secondary foldings have been proposed for these 3′ ends. The question therefore remained as to how these structures could be recognized by tRNA‐specific enzymes. We have established the minimum number of nucleotides from the 3′ end of the brome mosaic virus and broad bean mottle virus RNAs required for the formation of structures recognized by the tyrosyl‐tRNA synthetase and/or the tRNA nucleotidyltransferase. The results obtained delineate the length of the tRNA‐like region, and indicate that the 5′ region of the tRNA‐like structure participates in the formation of the amino acid stem. This has led us to propose an ‘L’‐shaped secondary structure for these tRNA‐like regions.

Turnip yellow mosaic virus (TYMV) contains a tRNA-like structure as an integral part of its genome. This structure is located at the extreme 3' end of the viral RNA and is the acceptor of valine after 3'-terminal adenylation. It is known that in vitro (with bacterial, yeast, or plant systems) and in vivo (upon microinjection into Xenopus laevis oocytes) a series of tRNA-specific enzymes can recognize this structure in the viral RNA. We report that TYMV RNA is valylated and consequently adenylated in vivo in its natural host, Chinese cabbage leaves. This suggests that the acylated form of the viral RNA could play an important role in the life-cycle of the virus.

This paper describes the minimum length of the turnip yellow mosaic virus (TYMV) RNA necessary to fulfill the tRNA-like properties of the viral RNA: 50 to 75 nucleotides and 86 nucleotides from the 3' end of TYMV RNA are sufficient for adenylation and valylation respectively by the Escherichia coli system. The size of the tRNA-like fragments obtained in vitro in the presence of an E. coli, a reticulocyte or a chinese cabbage leaf extract has also been determined. Among the major fragments liberated from the 3' end of TYMV RNA by the three systems are fragments of 117 and 112 nucleotides. In addition, the E. coli extract liberates fragments of 139 and 61 nucleotides, and the reticulocyte lysate fragments of 109, 94, 84, 73 and 46 nucleotides. The cleavage of the viral RNA by several systems in vitro to yield RNA fragments encompassing the tRNA-like sequence suggests that such fragments might also be liberated in vivo.

All structural studies of ribonucleic acids (RNAs) from various origins—be they cellular messenger RNAs or viral RNAs—show that these molecules contain nucleotide sequences that are not translated into polypeptides. At the 5' end, besides the “cap” structure generally found in eukaryotic mRNAs and viral RNAs, the untranslated sequence is heteropolymeric and of variable length—from a few nucleotides to a few hundred nucleotides. The physiological role of these untranslated heteropolymeric regions is not well understood. This chapter summarizes the results obtained with different viral RNAs that accept an amino acid and are recognized by various tRNA-specific enzymes. For a number of these viral RNAs, the nucleotide sequence of the amino-acid-acceptor regions has been determined and the structures have been compared. Results indicated that different primary and secondary structures of two nucleic acid molecules, such as tRNAs and certain viral RNAs, can be recognized efficiently by the same enzyme systems that play a central role in the transfer of genetic information. The nucleotide sequence of virtually all tRNA molecules can be drawn in a hydrogen-bonded “cloverleaf” structure. The existence of this structure, further folded into a tertiary structure, has been proved by X-ray diffraction analyses. The chapter concludes with a discussion on the possible role of tRNA-like structures in viral RNA genomes.

FOUR different DNA polymerases have so far been described in animal cells. Two of them are present in all types of cells1–5: the low molecular weight nuclear DNA polymerase, and the high molecular weight cytoplasmic DNA polymerase. The concentration of only the latter varies during the cell cycle, suggesting its involvement in DNA replication6. The two other DNA polymerases seem to exist only in certain cell types: the first, recently characterised7, seems to be directed by RNA, although differing from the oncornavirus reverse transcriptase8; the second is terminal deoxynucleotidyltransferase which does not exhibit the usual properties of DNA polymerases since it catalyses the polymerisation of deoxyribonucleotides in the absence of template by adding them randomly to the 3′OH end of oligo- or polydeoxyribonucleotides9,10. This last enzyme is tissue-specific: it exists only on the thymus of the different species tested11. Recently the terminal transferase was also identified in blood lymphoblasts of a child suffering from acute lymphoblastic leukaemia12.

Turnip yellow mosaic virus (TYMV) RNA treated with snake venom phosphodiesterase accepts cytidine 5′-monophosphate and adenosine 5′-monophosphate (AMP) when it is incubated in the presence of cytidine 5′-triphosphate (CTP), adenosine 5′-triphosphate, and Escherichia coli transfer RNA nucleotidyltransferase; untreated TYMV RNA accepts only AMP. When α 32 PCTP was used for terminal labeling, the nearest neighbor analyses and the anallyses after action of various nucleases showed that the sequence of five nucleotides at the 3′ end of TYMV RNA is: pGpCpApCpC. A nuclease present in commerical preparations of snake venom phosphodiesterase leads to the fragmentation of TYMV RNA, the 3′ end of which is found in a fragment having a sedimentation constant close to 5 s .

The synthesis of an insoluble tRNA nucleotidyltransferase by covalent coupling of the enzyme to cyanogen bromide‐activated sepharose is described. The sepharose‐bound enzyme is active in the repair of the pCpCpA sequence of tRNA. Most of its properties are identical to the soluble enzyme although its stability, regarding thermal inactivation and trypsin digestion, is increased. However, tRNA, which protects the soluble enzyme against thermal denaturation and protease digestion, surprisingly does not protect the sepharose‐bound enzyme.

FEBS LettersVolume 18, Issue 1 p. 130-134 Full-length articleFree Access Chick embryo poly (rA:dT)-dependent DNA polymerase J.C.C. Maïa, J.C.C. Maïa Institut de Biologie Moléculaire, Faculté des Sciences 9, Quai Saint-Bernard, Paris 5o, France Post doctorat fellow of the fundaçao de Amparo a Pesquisa do Estato de Sao Paolo and of the Ministère des Affaires Etrangères de France. Search for more papers by this authorF. Rougeon, F. Rougeon Institut de Biologie Moléculaire, Faculté des Sciences 9, Quai Saint-Bernard, Paris 5o, FranceSearch for more papers by this authorF. Chapeville, F. Chapeville Institut de Biologie Moléculaire, Faculté des Sciences 9, Quai Saint-Bernard, Paris 5o, FranceSearch for more papers by this author J.C.C. Maïa, J.C.C. Maïa Institut de Biologie Moléculaire, Faculté des Sciences 9, Quai Saint-Bernard, Paris 5o, France Post doctorat fellow of the fundaçao de Amparo a Pesquisa do Estato de Sao Paolo and of the Ministère des Affaires Etrangères de France. Search for more papers by this authorF. Rougeon, F. Rougeon Institut de Biologie Moléculaire, Faculté des Sciences 9, Quai Saint-Bernard, Paris 5o, FranceSearch for more papers by this authorF. Chapeville, F. Chapeville Institut de Biologie Moléculaire, Faculté des Sciences 9, Quai Saint-Bernard, Paris 5o, FranceSearch for more papers by this author First published: October 15, 1971 https://doi.org/10.1016/0014-5793(71)80427-1Citations: 26 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume18, Issue1October 15, 1971Pages 130-134 ReferencesRelatedInformation

Already described in bacteria, the peptidyl-tRNA hydrolase, which catalyzes the hydrolysis of the ester linkage that binds an N-acyl-amino acid or a polypeptide to tRNA, is shown here to be also present in plant and animal cells. In E. coli, 20 p. 100 of the enzyme is recovered bound to ribosomes, and the remaining 80 p. 100 is free. The ribosome-bound enzyme retains its activity. The enzyme can be removed from the ribosomes by repeated washing with 0.1 M ammonium chloride in normal undissociating conditions and also in the presence of low magnesium ion concentrations which dissociate the 70 S particles into their subunits. Magnesium ions appear to be involved in the binding of the enzyme to the ribosomes. When the enzyme is incubated in the presence of the acPhe-tRNA—ribosome—polyU complex, it does not hydrolyze the bound acPhe-tRNA.