[Congenital penile curvature: Guidelines from the Andrology and Sexual Medicine Committee of the French Association of Urology (CAMS-AFU)]

INTRODUCTION

Guidelines regarding congenital penile curvature (CPC) are lacking, and this pathology has not been the subject of French recommendations to date. The Andrology and Sexual Medicine Committee (CAMS) of the French Association of Urology (AFU) propose a series of clinical practice recommendations (CPR) by answering five clinical questions concerning the diagnosis and treatment of this pathology.

MATERIALS AND METHODS

After a bibliographic research between 2000 and 2021, followed by a critical reading according to the CRP method. These recommendations were written to answer five questions: (1) What are the different types of CPC? (2) What are the reasons for consultation? (3) What are the assessment methods for CPCs and their consequences? (4) What are the indications for CPCs treatment? (5) What are the corrective modalities for the treatment of CPC?

RESULTS

There are two main phenotypes: CPC type 4 (the most common) and chordee without hypospadias. The diagnosis of CPC is clinical and established through enquiry and clinical examination associated with photos of the erect penis. Support can be offered if the curvature is responsible for a disability and/or sexual dissatisfaction linked to a deformation making penetration difficult and/or in the event of significant psychological impact. Only surgical treatments have demonstrated their effectiveness. For type 4 CPCs, corporoplasty (excisional, incisional, or incisionless techniques) is the gold standard.

CONCLUSION

These recommendations provide support for the management of patients consulting with CPC.

Plasmonic Metasurfaces for Specific SERS Detection of Shiga Toxins

The interest in the development of nanoscale plasmonic technologies has dramatically increased in recent years. The photonic properties of plasmonic nanopatterns can be controlled and tuned via their size, shape, or the arrangement of their constituents. In this work, we propose a 2D hybrid metallic polymeric nanostructure based on the octupolar framework with enhanced sensing property. We analyze its plasmonic features both numerically and experimentally, demonstrating the higher values of their relevant figures of merit: we estimated a surface-enhanced Raman spectroscopy (SERS) enhancement factor of 9 × 10⁷ and a SPR bulk sensitivity of 430 nm/RIU. In addition, our nanostructure exhibits a dual resonance in the visible and near-infrared region, enabling our system toward multispectral plasmonic analysis. Finally, we illustrate our design engineering strategy as enabled by electron beam lithography by the outstanding performance of a SERS-based biosensor that targets the Shiga toxin 2a, a clinically relevant bacterial toxin. To the best of our knowledge, this is the first time that a SERS fingerprint of this toxin has been evidenced.

[French Urological Association (AFU) guidelines for Peyronie's disease assessment and treatment]

INTRODUCTION

Peyronie's disease is a common cause for consultation in urology. Many controversies surround its treatment. No French Guidelines have been published so far. The Committee of Andrology and Sexual Medicine of the French Association of Urology therefore offers a series of evidence-based recommendations.

MATERIALS AND METHODS

These recommendations are made according to the ADAPTE method, based on European (EAU, ESSM), American (AUA, ISSM) and Canadian (CAU) recommendations, integrating French specificities due to the availability of treatments, and an update of the recent bibliography.

RESULTS

The assessment of the disease is clinical. Patients with functional impairment or significant psychological repercussions may be offered treatment. The benefits and drawbacks of each treatment should be explained to the patient. Regarding non-surgical treatments, no available treatment has market authorization in France. Vitamin E is not recommended. Analgesic (oral or low-intensity shock waves) or proerectile treatments may be offered as needed, as well as traction therapy. Due to the unavailability of collagenase injections, verapamil injections may be offered. Surgical treatments are to be considered in the stabilized phase of the disease, and consist of performing a plication, an incision-graft or the placement of a penile implant according to the patient's wishes, the curvature and the penis size, as well as erectile function. Combination treatments can be offered.

CONCLUSION

The management of Peyronie's disease is complex, and the levels of evidence for treatments are generally low. The success of treatment will depend on the quality of the initial assessment, the patient's information and understanding of the expected effects, and the practitioner's experience.

[Recommendations of the Committee of Andrology and Sexual Medicine of the AFU concerning the management of Varicocele]

The diagnosis of varicocele is clinical, carried out in supine and standing position and in Valsalva maneuver. Only clinical varicoceles have to be treated. A scrotal ultrasound with Doppler is generally performed as part of the infertile man's evaluation or in case of examination difficulties. The main indication for varicocele treatment is the adult man with clinical varicocele and abnormalities of sperm parameters, in a context of infertility of couple, with a partner having a satisfactory ovarian reserve and no cause of female infertility or a curable infertility cause. The decision to treat varicocele must therefore be taken after evaluation of the two partners of the couple. Adults with symptomatic varicocele and those with spermogram abnormalities may also be offered a cure for their varicocele even in the absence of a paternity plan, as well as adolescents with reduced testicular growth, an ipsilateral decrease testicular volume, or a size gradient between the 2 testes. The cure of varicocele can be carried out by surgery or by percutaneous embolization. Microsurgery (inguinal or subinguinal) offers lower rates of recurrence and complications than high surgical approaches (laparoscopic or not) and surgeries without magnification. It is therefore the reference surgical technique. Percutaneous retrograde embolization is a minimally invasive alternative to microsurgery offering satisfactory outcomes with rare and often benign complications. The cure for varicocele results in an improvement in sperm parameters and recent data seem to confirm that it increases the natural pregnancy rate. These results appear after a delay of 3 to 9 months (at least 1 to 2 cycles of spermatogenesis). When the sperm involvement was severe (azoospermia, severe oligospermia), the improvement of the spermogram allow (1) to avoid surgery testicular sperm extraction or (2) perform intrauterine insemination rather than ICSI.

[Biotherapies for erectile dysfunction and Peyronie's disease: Where are we now?]

INTRODUCTION

Clinical trials of cell therapy for erectile dysfunction (ED) and Peyronie's disease (PD) were recently conducted after preclinical studies.

AIMS

The aims of this study are to give an update on biotherapy for ED and PD and to describe the regulatory framework for these therapies.

MATERIALS AND METHODS

A literature review was performed through PubMed and Clinical.trials.gov addressing cell therapy for ED and PD and using following keywords "erectile dysfunction", "Peyronie's disease", "stem cell", and "platelet-rich plasma".

RESULTS

Preclinical studies in rodent models have shown the potential benefit of cell therapy for ED after radical prostatectomy or caused by metabolic diseases, and PD. The tissues used to obtain the therapeutic product were bone marrow, adipose tissue and blood (PRP, platelet-rich plasma). Mechanism of action was shown to be temporary and mainly paracrine. Four clinical trials were published concerning ED after radical prostatectomy and in diabetic patients and one for PD. Eleven clinical trials including three randomized trials are currently going on. Preclinical and preliminary clinical results suggested the possibility to improve spontaneous erectile function and response to pharmaceutical treatment in initially non-responder patients. This effect is mediated by an improvement of penile vascularization. A reduction of penile curvature without side effect was noted after injections into the plaque of PD patients. Most of these therapeutic strategies using autologous cells were considered as "Advanced Therapy Medicinal Products" with strict regulatory frameworks imposing heavy constraints, in particular in case of "substantial" modification of the cells. The regulatory framework remains unclear and more permissive for PRP and cell therapy processes with extemporaneous preparation/injection and no "substantial" modifications.

CONCLUSIONS

First results on cell therapy for ED and PD are promising. The regulatory framework can significantly change according to cell preparations and origins leading to various constraints. This regulatory framework is crucial to consider for the choice of the procedure.

[Recommendations of the Committee of Andrology and Sexual Medicine of the AFU concerning the management of andrological and sexual medicine pathologies during the COVID-19 crisis]

OBJECTIVE

To assist urologists in the management of andrological and sexual medicine pathologies during the COVID-19 crisis.

MATERIAL AND METHOD

Use of the formalized consensus method.

RESULTS

The medical and surgical management of patients in andrology and sexual medicine must be adapted. Consultations should, as far as possible, be carried out by tele-consultation. For operative procedures, the delay between the operative decision and the date of (re)scheduling of the procedure will depend on: (1) the level of criticality of the clinical situation; (2) the type of intervention; (3) the functional and psychological repercussions, including quality of life while waiting for the procedure; (4) the notion of losing the chance of having an optimal outcome; (5) the risk of potential complications from delaying a procedure for too long; and (6) taking into account the patient's risk factors for severe forms of COVID-19. The protection of urologists from COVID-19 should be considered. Each urologist must make the best decision for the patient, taking into account the acceptable time frame and quality of life impact before surgical management, the COVID risk parameters, the technical and anesthetic feasibility and the structural possibility of the health care institution to ensure a specific dedicated pathway during the COVID-19 health crisis.

CONCLUSION

The management of andrological and sexual medicine pathologies must be adapted to the COVID-19 crisis context. Some patients may require surgery, including in emergency. These recommendations are transitional and will end with the COVID-19 crisis.

Priapisme veineux aigu aux urgences : procédure fondée sur une revue systématique de la littérature

Le priapisme veineux aigu (PVA) est urgent en raison de séquelles érectiles éventuelles. Sa rareté et l’absence de procédure expliquent des traitements encore inégaux, peu normés.

Objectif : Optimiser la prise en charge initiale d’un PVA grâce à une procédure décisionnelle, adaptée aux urgentistes.

Matériel et méthode : Une revue systématique de la littérature recense les algorithmes schématisés ainsi que des articles de revue et mises au point récents. Les critères diagnostiques et thérapeutiques ont été analysés puis comparés pour vérifier s’ils répondaient aux besoins. La validation de cette procédure par des experts a été recherchée. Résultats : L’originalité de notre procédure réside dans sa cible (urgentistes), sa hiérarchisation, « Que faire ? Comment faire ? Quand faire ? Qui fait ? », de façon graduée et séquentielle via une chronologie détaillée, et une priorité donnée à la gazométrie caverneuse, fil conducteur de la prise en charge, facilement disponible. À cela s’ajoutent des tableaux, des check-lists (contexte étiologique et souffrance ischémique), des schémas descriptifs des traitements médicaux indiqués en première ligne (technique, matériel de ponction décompressive et d’injection intracaverneuse d’alpha-stimulant), critères de recours à l’urologue, suivi et hospitalisation. Cette procédure a été validée par le conseil scientifique du réseau nord-alpin des Urgences, le comité d’andrologie et médecine sexuelle de l’Association française d’urologie.

Conclusion : Facile à utiliser, cette procédure inédite répond à un réel besoin. Son appropriation et sa diffusion s’inscrivent dans une démarche qualité adaptée au parcours de soins du PVA en France afin de prévenir les séquelles érectiles de cette urgence affectant majoritairement des sujets jeunes.

Nucleotides U28-A42 and A37 in unmodified yeast tRNA(Trp) as negative identity elements for bovine tryptophanyl-tRNA synthetase

Wild-type bovine and yeast tRNA(Trp) are efficiently aminoacylated by tryptophanyl-tRNA synthetase both from beef and from yeast. Upon loss of modified bases in the synthetic transcripts, mammalian tRNA(Trp) retains the double recognition by the two synthetases, while yeast tRNA(Trp) loses its substrate properties for the bovine enzyme and is recognised only by the cognate synthetase. By testing chimeric bovine-yeast transcripts with tryptophanyl-tRNA synthetase purified from beef pancreas, the nucleotides responsible for the loss of charging of the synthetic yeast transcript have been localised in the anticodon arm. A complete loss of charging akin to that observed with the yeast transcript requires substitution in the bovine backbone of G37 in the anticodon loop with yeast A37 and of C28-G42 in the anticodon stem with yeast U28-A42. Since A37 does not prevent aminoacylation of the wild-type yeast tRNA(Trp) by the beef enzyme, a negative combination apparently emerges in the synthetic transcript after unmasking of U28 by loss of pseudourydilation.

Shiga toxin 1: damage to DNA in vitro

Shiga toxins share with plant ribosome-inactivating proteins the same enzymatic mechanism of action: the removal of a specific adenine from 28S RNA when acting on ribosomes and the removal of multiple adenines when acting on DNA in vitro. The activity on DNA, only recently reported, is particularly evident, and has been studied mostly at acidic pH. For the in vitro activity, on both ribosomes and DNA, Shiga toxins require activation by trypsin, urea and dithiothreitol which release the enzymatically active A(1) fragment. Activation by the classical procedure leaves large amounts of urea and DTT which interfere in the DNA depurination assay and completely abolish depurination at physiological pH. A consistent release of [3H]adenine from DNA at neutral pH is instead observed when the toxin is activated in vitro by an improved method which removes most of the drastic reagents required for proteolytic cleavage and reduction. Damage to single-stranded DNA by Shiga toxin 1 (Stx1) primarily involves depurination. A spontaneous DNA breakdown appears in fact only after extensive base removal, a behavior similar to that observed with uracil-DNA glycosylase, a simple glycosylase devoid of lyase activity. NaCl inhibits the activity of Stx1, probably by minimizing the sliding distance traveled by the enzyme along DNA in search of its target sites and promoting dissociation of the substrate-enzyme complex.

A survey of adenine and 4-aminopyrazolo[3,4-d]pyrimidine (4-APP) as inhibitors of ribosome-inactivating proteins (RIPs)

The inhibitory power of adenine and 4-aminopyrazolo[3,4-d]pyrimidine (4-APP) on the RNA-N-glycosidase activity catalyzed by bacterial (Shiga toxin 1) and plant (ricin, gelonin, momordin, bryodin-R, PAP-S, luffin, trichosantin, saporin 6 and barley) RIPs has been compared. The behavior of the two inhibitors is largely variable. While Shiga toxin 1 is preferentially inhibited by 4-APP, plant RIPs are either preferentially inhibited by adenine, or equally inhibited by the two compounds or, finally, only slightly more by 4-APP. Sequence variabilities involved in these different behaviors are discussed. The experimental data clearly indicate that, in spite of the same mechanism of action, RIPs differ widely in the ability to fit small ring molecules in the active cleft. While the strong inhibitory power of 4-APP on Shiga toxin 1 opens perspectives of therapeutic interventions, the ineffectiveness of the compound on ricin precludes its use as a suitable antidote in poisoning.

4-Aminopyrazolo[3,4-d]pyrimidine (4-APP) as a novel inhibitor of the RNA and DNA depurination induced by Shiga toxin 1

Shiga toxin 1 (Stx1) catalyses the removal of a unique and specific adenine from 28S RNA in ribosomes (RNA-N-glycosidase activity) and the release of multiple adenines from DNA (DNA glycosylase activity). Added adenine behaves as an uncompetitive inhibitor of the RNA-N-glycosidase reaction binding more tightly to the Stx1-ribosome complex than to the free enzyme. Several purine derivatives and analogues have now been assayed as inhibitors of Stx1. Most of the compounds showed only minor differences in the rank order of activity on the two enzymatic reactions catalysed by Stx1. The survey highlights the importance of the amino group in the 6-position of the pyrimidine ring of adenine. Shifting (2-aminopurine) or substituting (hypoxanthine, 6-mercapto-purine, 6-methylpurine) the group greatly decreases the inhibitory power. The presence of a second ring, besides the pyrimidine one, is strictly required. Substitution, by introducing an additional nitrogen, of the imidazole ring of adenine with triazole leads to loss of inhibitory power, while rearrangement of the nitrogen atoms of the ring from the imidazole to the pyrazole configuration greatly enhances the inhibitory power. Thus 4-aminopyrazolo[3,4-d]pyrimidine (4-APP), the isomer of adenine with the five-membered ring in the pyrazole configuration, is by far the most potent inhibitor of both enzymatic reactions catalysed by Stx1. This finding opens perspectives on therapeutic strategies to protect endothelial renal cells once endocytosis of Stx1 has occurred (haemolytic uraemic syndrome). In the RNA-N-glycosidase reaction 4-APP binds, as adenine, predominantly to the Stx1-ribosome complex (uncompetitive inhibition), while inhibition of the DNA glycosylase activity by both inhibitors is of the mixed type.

Identity elements in bovine tRNA(Trp) required for the specific stimulation of gelonin, a plant ribosome-inactivating protein

Ribosome-inactivating proteins (RIPs) are RNA-N-glycosidases widely present in plants that depurinate RNA in ribosomes at a specific universally conserved position, A4324, in the rat 28S rRNA. A small group of RIPs (cofactor-dependent RIPs) require ATP and tRNA to reach maximal activity on isolated ribosomes. Among cofactor-dependent RIPs, gelonin is specifically and uniquely stimulated by tRNA(Trp). The active species are avian (chicken) and mammalian (beef, rat, and rabbit) tRNA(Trp), whereas yeast tRNA(Trp) is completely devoid of stimulating activity. In the present article, bovine and yeast tRNA(Trp) with unmodified bases were prepared by assembly of the corresponding genes from synthetic oligonucleotides followed by PCR and T7 RNA polymerase transcription of the amplified products. The two synthetic tRNAs were fully active (bovine) or inactive (yeast) as the wild-type tRNAs. Construction of chimeric tRNA(Trp) transcripts identified the following bovine nucleotides as recognition elements for gelonin-stimulating activity: G26 and bp G12-C23 in the D arm and G57, A59, and bp G51-C63 and U52-A62 in the T arm. Among single-stranded nucleotides, A59 has a prominent role, but full expression of the gelonin-stimulating activity requires an extensive cooperation between nucleotides in both arms.

Identification of the tRNAs which up-regulate agrostin, barley RIP and PAP-S, three ribosome-inactivating proteins of plant origin

Ribosome-inactivating proteins (RIP) are RNA-N-glycosidases widely diffused in plants which depurinate ribosomal RNA at a specific universally conserved position, A4324 in rat ribosomes. A small group of RIPs (cofactor-dependent RIPs) require ATP and tRNA to reach maximal activity on isolated ribosomes. The tRNA which stimulates gelonin was identified as tRNA(Trp). The present paper reports the identification of three other tRNAs which stimulate agrostin (tRNA(Ala)), barley RIP (tRNA(Ala), tRNA(Val)) and PAP-S (tRNA(Gly)), while for tritin-S no particular stimulating tRNA emerged. The sequences of tRNA(Val) and tRNA(Gly) correspond to the already known ones (rabbit and man, respectively). The tRNA(Ala) (anticodon IGC) identifies a new isoacceptor. Only the stimulating activity of the tRNA(Ala) for agrostin approaches the specificity previously observed for the couple gelonin-tRNA(Trp).

Uncompetitive inhibition by adenine of the RNA-N-glycosidase activity of ribosome-inactivating proteins

Ricin is a member of the ribosome-inactivating protein (RIP) family with RNA-N-glycosidase activity which inactivates eukaryotic ribosomes by specifically removing adenine from the first adenosine of a highly conserved GAGA loop present in 28S rRNA. Free adenine protects ribosomes in cell-free systems from inactivation by ricin. Protection by adenine is highly specific, since AMP, adenosine and modified adenines (1-methyladenine and ethenoadenine) were completely ineffective. Kinetic analysis of the behaviour of adenine as inhibitor of the RNA-N-glycosidase reaction catalysed by ricin, Shiga-like toxin I and momordin, two other members of the RIP family, established that inhibition was of the uncompetitive type, the inhibitor binding to the enzyme-substrate complex. Adenine did not protect ribosomes from alpha-sarcin, an RNAase that inactivates ribosomes by cleaving the phosphodiester bond located in the GAGA loop at one nucleotide distance from the adenosine depurinated by the RNA-N-glycosidases. Adenine at the concentration of 1 mM lowered 1.5-fold the toxicity of ricin and 3.7-fold that of Shiga-like toxin I on Vero cells in culture. The same concentration of adenine decreased 2.4-fold the inactivation of isolated ribosomes by ricin, 2.8-fold the inactivation by Shiga-like toxin I and 20-fold that by momordin.

The RNA-N-glycosidase activity of Shiga-like toxin I: kinetic parameters of the native and activated toxin

Shiga toxin and Shiga-like toxins are ribosome-inactivating proteins with RNA-N-glycosidase activity which remove a specific adenine from 28S RNA. The toxins are composed of an A subunit non-covalently associated to a multimer of receptor-binding B subunits. Near the COOH-terminus of the A subunit, a disulfide-bonded loop contains two trypsin-sensitive arginine residues. Proteolytic nicking at these sites, followed by reduction, removes from the A subunit the C-terminal end together with the associated B subunits. The requirement of such cleavage for biological activity of Shiga toxin and Shiga-like toxins has been recently questioned. The present paper reports the kinetic constants of the adenine release from highly purified Artemia salina ribosomes catalysed by Shiga-like toxin I and by its A subunit before and after treatment with trypsin, urea and dithiothreitol or urea and dithiothreitol alone. All reactions had approximately the same Km (1 microM). The Kcat was 0.6 min-1 for the untreated holotoxin and 6 min-1 for the isolated A subunit, respectively. The trypsin treatment increased 1000-fold the Kcat of the holotoxin (770 min-1) and 100-fold the Kcat of the A subunit (640 min-1). The same Kcat (693 min -1) was also observed when the A subunit was treated only with urea and dithiothreitol. Thus the full activity of Shiga-like toxin I required not only removal of the B subunits but also activation of the A subunit itself. Such activation could be largely induced in vitro by drastic loosening of the molecule induced by urea and dithiothreitol, but in vivo would probably require a proteolytic cleavage of the toxin. Inactivation of ribosomes by Shiga-like toxin I did not require sensitization of ribosomes by ATP and macromolecular cofactors present in postribosomal supernatants.

tRNA(Trp) as cofactor of gelonin, a ribosome-inactivating protein with RNA-N-glycosidase activity. Features required for the cofactor activity

Purified beef and rabbit liver tRNA(Trp), but not yeast tRNA(Trp), increase the in vitro inactivation of eukaryotic ribosomes by gelonin, a ribosome-inactivating protein with RNA-N-glycosidase activity on 28S rRNA. Aminoacylation and stepwise trimming of the 3'-end of bovine tRNA(Trp) affect the cofactor activity, the most active species being that shortened by the last two nucleotides. ATP only moderately increases the activity of purified mammalian tRNA(Trp) and in this increase the cognate aminoacyl-tRNA synthetase apparently has no role. Mobility shift experiments indicate that bovine tRNA(Trp) binds both to ribosomes and to gelonin and favours the dissociation of gelonin from ribosomes.

Differential up-regulation by tRNAs of ribosome-inactivating proteins

Some plant ribosome-inactivating proteins (RIPs) with RNA-N-glycosidase activity on 28S RNA require, for the inactivation of ribosomes, the presence of macromolecular cofactors present in post-ribosomal supernatants. In the case of gelonin one of the cofactors is tRNATrp lacking one or two nucleotides at the 3'-CCA end [Brigotti, M., Carnicelli, D., Alvergna, P., Pallanca, A., Lorenzetti, R., Denaro, M., Sperti, S. and Montanaro, L. (1995) Biochem. J. 310, 249-253]. In the present study it is shown that tRNAs are involved in the up-regulation of all the cofactor-requiring RIPs up to now identified (agrostin, barley RIP, PAP and tritin, besides gelonin). Polyacrylamide gel electrophoresis shows that tRNA fractions with different mobilities stimulate different RIPs. With the identification of agrostin, the cofactor-requiring RIPs (italics) add to five out of a total of thirteen investigated: barley RIP, bryodin-R, gelonin, lychnin, momordin, momorcochin-S, PAP, saporin-6, tritin [Carnicelli, D., Brigotti, M., Montanaro, L. and Sperti, S. (1992) Biochem. Biophys. Res. Commun. 182, 579-582], agrostin, luffin, trichokirin and trichosanthin (present study).

3'-immature tRNA(Trp) is required for ribosome inactivation by gelonin,a plant RNA N-glycosidase

Inactivation of ribosomes by gelonin, a ribosome-inactivating protein with RNA N-glycosidase activity on 28 S rRNA, requires macromolecular cofactors present in post-ribosomal supernatants. One of these cofactors has been purified from a rat liver extract and identified as an RNA about 70 nt long which in sequence analysis shows a high level of similarity with mammalian (bovine) tRNA(Trp). The pattern of the sequencing gel is consistent with the co-existence in the preparation of two 3'-immature tRNA(Trp) species, missing only A75, or both A75 and C74. In the presence of ATP, CTP and tRNA nucleotidyltransferase, the gelonin-stimulating RNA is a good acceptor of tryptophan. An oligodeoxynucleotide complementary to positions 55 to 72 of mammalian (bovine) tRNA(Trp) hybridizes with the gelonin-stimulating RNA as demonstrated by gel mobility shift and ribonuclease H digestion. The oligodeoxynucleotide-directed ribonuclease H treatment also abolishes the gelonin-promoting activity of crude preparations of RNA, giving strong evidence that the only active RNA is a tRNA(Trp)-like molecule.

RNA present in post-ribosomal supernatants makes ribosomes susceptible to inactivation by gelonin and alpha-sarcin

The remarkable resistance of isolated ribosomes to gelonin is overcome by cofactors present in post-ribosomal supernatants. In rat liver post-ribosomal supernatant RNA is the cofactor responsible of the sensitization of ribosomes. Isolated RNA, which consists mostly of deacylated tRNA, accounts for less than 10 per cent of the activity of the original supernatant. The activity of the supernatant is completely destroyed by micrococcal nuclease and RNAase A and also by proteinase K, suggesting that some protein enhances the effect of RNA. RNA has a role also in the sensitization of ribosomes to alpha-sarcin, an RNAase which inactivates ribosomes by hydrolyzing a single phosphodiester bond in the same region of 28S rRNA which is the target of the N-glycosidase activity of gelonin.

Oligonucleotides complementary to the alpha-sarcin domain of 28S rRNA inhibit cell-free protein synthesis

Oligodeoxynucleotides complementary to the alpha-sarcin domain of rat 28S rRNA inhibit cell-free protein synthesis. The poly(U) translation system containing Artemia salina ribosomes was more sensitive to inhibition than the system containing rat liver ribosomes. The 21-mer, which was the most effective of the 7 oligonucleotides tested, hybridized with naked 28S rRNA. Hybridization with whole ribosomes, assayed by S1 nuclease protection, occurred only at high ionic strength or with ribosomes actively engaged in protein synthesis.

Partial purification of two proteins which sensitize ribosomes to gelonin: sensitization is not linked to phosphorylation of ribosomal proteins

Inactivation of ribosomes by gelonin, from Gelonium multiflorum, requires ATP and extraribosomal protein(s) present in the rabbit reticulocyte lysate [SPERTI, S. et al. (1991) Biochem. J. 277, 281-284]. On the anion exchanger Mono Q the activity responsible for the sensitization of ribosomes to gelonin resolves in two peaks which both display a kinase activity on ribosomal proteins. However, staurosporin, an inhibitor of several protein kinases, strongly inhibits phosphorylation of ribosomal proteins without affecting the gelonin-promoting activity of Mono Q peaks. All the evidence collected contradicts a direct link between sensitization to gelonin and phosphorylation of ribosomes.

Ribosome-bound elongation factor 2 escapes phosphorylation by Ca2+/calmodulin-dependent protein kinase III

The activity of eukaryotic elongation factor 2 is regulated by phosphorylation catalysed by a highly specific Ca2+/calmodulin-dependent protein kinase. Phosphorylated EF2 binds to ribosomes with decreased affinity. The present evidence indicates that EF2 prebound to ribosomes is protected from phosphorylation, just as earlier evidence indicated that ribosome-bound EF2 is protected from ADP-ribosylation catalysed by diphtheria toxin. Ribosome-inactivating proteins ricin and gelonin, by interfering with the EF2-ribosome interaction, allow full phosphorylation of EF2.

Differential requirement of ATP and extra-ribosomal proteins for ribosome inactivation by eight RNA N-glycosidases

The requirement of ATP and extra-ribosomal proteins for the inactivation of ribosomes by eight plant RNA N-glycosidases [ribosome-inactivating proteins (RIPs)] was investigated. Tritin, pokeweed antiviral protein and barley RIP depend, as gelonin [Sperti, S., Brigotti, M., Zamboni, M., Carnicelli, D. and Montanaro, L. (1991) Biochem. J., 277, 281-284], on the presence of ATP and extra-ribosomal proteins for full inactivation of ribosomes, while bryodin, lychnin, momordin, momorcochin and saporin inactivate isolated Artemia salina ribosomes suspended in buffer saline.