<i>The Greater Roman Historians</i>. M. L. W. Laistner

Hammond, Mason

doi:10.2307/2850457

Cited by 4 publications

(4 citation statements)

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“…Recently, it has been shown that in reticulocyte extracts the normally inefficient translation of rp mRNA can be increased by addition of eucaryotic initiation factors 4F and 3 [35]. Although this result clearly indicates that the binding of mRNA to the 43s initiation complex is a crucial step in rp-mRNA translation, it does not exclude the involvement of other specific factors.…”

Section: Discussionmentioning

confidence: 87%

Translational regulation of ribosomal protein synthesis in Xenopus cultured cells: mRNA relocation between polysomes and RNP during nutritional shifts

Loreni

Amaldi

1992

European Journal of Biochemistry

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Translational control of ribosomal protein mRNA was analyzed in a Xenopus cell line during growth-rate changes induced by serum deprivation and readdition. After being transferred into serum-free medium, the cells rapidly decrease their DNA, RNA and protein synthesis, while addition of serum to the culture after a few hours of deprivation causes a rapid recovery. During these growth-rate changes, we observed a shift in ribosomal protein mRNA distribution between polysomes and RNP. The proportion of mRNA on polysomes for the four ribosomal proteins analyzed changed from 70-80% during rapid growth to 25-35% during the downshift and back to 70-80% after the upshift. Northern blot analysis showed that ribosomal protein mRNA level was constant during the shifts even in the presence of the transcriptional inhibitor actinomycin D. This indicates that the distribution changes were due to a reversible transfer of ribosomal protein mRNA between polysomes and RNP without altering mRNA stability. We have also compared the kinetics of ribosomal protein mRNA distribution changes with the kinetics of the changes in the partition of ribosomes between free monomers and polysomes. The results obtained show that the change in ribosomal protein mRNA localization is very fast, allowing short-term adjustments of ribosome synthesis rate. Moreover, our observations are consistent with the hypothesis that the amount of free ribosomes present in the cell could affect ribosomal protein mRNA utilization.

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Section: Discussionmentioning

confidence: 87%

Translational regulation of ribosomal protein synthesis in Xenopus cultured cells: mRNA relocation between polysomes and RNP during nutritional shifts

Loreni

Amaldi

1992

European Journal of Biochemistry

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“…Translation of these mRNAs may be cell-cycle-regulated [267]. The regulation of translation of ribosomal protein mRNAs has been linked with eIF4F function [269] or eIF4E phosphorylation [270], but overexpression of eIF4E did not prevent the translational repression of ribosomal protein mRNAs in NIH3T3 cells undergoing growth arrest in response to inhibitors of DNA synthesis [271]. An exciting, recent, observation is that the selective enhancement of translation of several of these mRNAs in growth-stimulated cells is impaired by the immunosuppressive drug, rapamycin [272,2731.…”

Section: Structures In the 5' Untranslated Region (5' Utr) Associatedmentioning

confidence: 99%

Initiation of Protein Synthesis in Eukaryotic Cells

Pain

1996

European Journal of Biochemistry

674

471

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It is becoming increasingly apparent that translational control plays an important role in the regulation of gene expression in eukaryotic cells. Most of the known physiological effects on translation are exerted at the level of polypeptide chain initiation. Research on initiation of translation over the past five years has yielded much new information, which can be divided into three main areas: (a) structure and function of initiation factors (including identification by sequencing studies of consensus domains and motifs) and investigation of protein-protein and protein-RNA interactions during initiation ; (b) physiological regulation of initiation factor activities and (c) identification of features in the 5' and 3' untranslated regions of messenger RNA molecules that regulate the selection of these mRNAs for translation. This review aims to assess recent progress in these three areas and to explore their interrelationships.Keywords: translation; initiation; mRNA ; review, regulation.In 1986 I published a review describing the mechanism and regulation of initiation of translation in mammalian cells 121. By that time most of the polypeptide initiation factors catalysing this process had been extensively purified and their individual activities studied in various in vitro systems. Several of them had been shown to be phosphoproteins and, in one case, eukaryotic initiation factor-2 (eIF-2), the effects of phosphorylation had been elucidated and two physiological kinases had been identified. There seemed to be a feeling in some circles that the most interesting problems in protein synthesis had been solved, and that only a few rather boring nuts and bolts awaited discovery.Over the intervening ten years there has been an explosion of research activity in this area, largely fuelled by information yielded by molecular biology and genetic techniques. Cloning of cDNAs encoding initiation factors has revealed domain structures indicative of function and potential regulatory mechanisms. Experiments exploiting the ability to elucidate and manipulate mRNA sequences have demonstrated that translational control contributes to changes in patterns of gene expression during growth, differentiation and development to an extent that would have seemed inconceivable in 1985. Such experiments have, in particular, revealed important roles for structural fea- UTR, untranslated region (in mRNA); RRM, RNA recognition motif; ORF, open reading frame; EMCV, encephalomyocarditis virus ; FMDV, foot-and-mouth disease virus ; IRES, internal ribosome entry segment ; PTB, polypyrimidine tract binding protein ; HCR, heme-controlled repressor; PKR, protein kinase activated by RNA; dsRNA, doublestranded RNA; p70ShK and p 9 0 k , 70 kDa and 90-92 kDa ribosomal protein S6 kinases ; GSK, glycogen synthase kinase ; IRE, iron-regulatory element; IRP, iron regulatory protein ; PABP, poly(A) binding protein; AMV, alfalfa mosaic virus ; CPE, cytoplasmic polyadenylation element (also known as ACE, adenylation control element); MAP, mitogenactivated protei...

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“…3lcCowin. and Shupe (4) found that inoculation of calves by injection of E. bovis oocysts into the abomasum caused as severe infections as inoculation by nippled flask or by gelatin capsules, supporting the finding that passage through the rumen is not essential for excystation of E. bovis oocysts. ,41so.…”

Section: Discussionmentioning

confidence: 76%

Excystation of Eimeria bovis and Other Species of Bovine Coccidia*

Nyberg¹,

Hammond²

1964

The Journal of Protozoology

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SYNOPSIS. Mechanically released sporocyts of Eimeria bovis, E. ellipsoidalis and E. auburnensis readily excysted when incubated in a mixture of trypsin, steapsin, and bovine bile. Excystation of intact E. bovis, E. ellipsoidalis and E. auburnensis oocysts occurred after pretreatment at 37°C in aqueous 0.02 M cysteine hydrochloride under an atmosphere of CO2‐air or CO2‐N2, followed by incubation in an enzyme‐bile mixture. Nine % of E. bovis oocysts were activated after 6 hr of incubation at 37 C in a mixture of 0.5% (w/v) trypsin, 0.5% (w/v) steapsin, and 5.0% (v/v) bile at pH 7.5 with 10 hr pretreatment under air and 20% CO2; with 30% CO2, 80% activation occurred; with 50% CO2, 91% of the oocysts were activated. At CO2 levels from 10 to 40%, pretreatment with CO2 and N2 yielded less activation than CO2 and air. Pretreatment with CO2‐N2 (50–50) for 2 hr resulted in 37% activation; for 6 hr, 60%; for 10 hr, 94%; and for 14 hr, 99%. After pretreatment under 50% CO2 for 10 hr, 95% excystation was obtained by incubation for 6 hr in 0.5% trypsin and 5.0% bile. Only 76 or 69% excystation occurred when 0.25% trypsin or 1.0% bile, respectively, was substituted. Addition of steapsin to this mixture caused little change in the results. In oocysts pretreated 14 to 21 hr with steapsin, 2% or less excystation occurred after 6 hr in a trysinbile or bile mixture. E. ellipsoidalis oocysts, pretreated for 10 hr under CO2‐N2 (50–50), underwent 61 and 80% excystation when incubated for 2 and 6 hr, respectively, in trypsin, steapsin, and bile. E. bovis oocysts enclosed in a dialysis bag inside an intestinal fistula became thinned or flattened at the micropyle after 24 hr, and excystation occurred when these oocysts were mixed with trypsin, steapsin, and bile and returned to the fistula for 4 hr. No excystation occurred when oocysts without added enzymes were left 48 hr in the fistula. Sporozoites escaped first from sporocysts and then from oocysts.

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The Greater Roman Historians. M. L. W. Laistner

Cited by 4 publications

References 0 publications

Translational regulation of ribosomal protein synthesis in Xenopus cultured cells: mRNA relocation between polysomes and RNP during nutritional shifts

Translational regulation of ribosomal protein synthesis in Xenopus cultured cells: mRNA relocation between polysomes and RNP during nutritional shifts

Initiation of Protein Synthesis in Eukaryotic Cells

Excystation of Eimeria bovis and Other Species of Bovine Coccidia*

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