Expression of the gene for ribosomal protein L1 in Xenopus embryos: alteration of gene dosage by microinjection (original) (raw)
Related papers
Nucleic Acids Research, 1992
We have analyzed several randomly selected mRNAs, of the relatively abundant category, on the basis of maternal or zygotic origin and translational efficiency at different developmental stages. For this purpose, clones from a Xenopus embryo cDNA library were hybridized with cDNA probes prepared with poly(A) +RNA from polysomes and from mRNPs of embryos at different stages. The results obtained indicate that the majority of the relatively abundant mRNAs (38 out of 61) is subject to some kind of translational regulation during embryogenesis. Moreover, 30 clones have been selected as corresponding to mRNAs that behave, from the point of view of transcriptional and translational regulation, similarly to previously studied ribosomal protein (rprotein) mRNAs. Sequence analysis of 20 of these selected cDNAs has shown that half of them are in fact homologous to already sequenced r-protein mRNAs. Unexpectedly we have found that also the mRNA for ca-cardiac actin and another mRNA homologous to creatine kinase M mRNA have a similar translational regulation during embryogenesis.
Translational inactivation of ribosomal protein mRNAs during Xenopus oocyte maturation
Genes & Development, 1988
Ribosomal protein synthesis ceases upon maturation of Xenopus oocytes. We find that this cessation results from the dissociation of ribosomal protein mRNAs from polysomes and is accompanied by the deadenylation of these transcripts. A synthetic mRNA encoding ribosomal protein L1, microinjected into stage VI oocytes, is deadenylated and released from polysomes upon maturation. Our results indicate that sequences located within 387 bp of the 3' terminus of L1 mRNA direct both the deadenylation and polysomal release of this ribosomal protein mRNA. The proper translational regulation of an exogenous ribosomal protein mRNA in microinjected oocytes provides a basis for determining the sequence specificity for the differential utilization of maternal mRNAs during oocyte maturation.
Translational regulation of ribosomal protein synthesis during xenopus development
Cell Differentiation and Development, 1989
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 serumfree 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 growthrate 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.
Molecular and cellular …, 1994
The gene encoding ribosomal protein LI in Xenopus laevis is known to be posttranscriptionally regulated; the third intron can be processed from the pre-mRNA in two alternative ways, resulting either in the production of LI mRNA or in the release of a small nucleolar RNA (U16). The formation of splicing complexes was studied in vivo by oocyte microinjection. We show that spliceosome assembly is impaired on the Li third intron and that the low efficiency of the process is due to the presence of suboptimal consensus sequences. An analysis of heterogeneous nuclear ribonucleoprotein (hnRNP) distribution was also performed, revealing a distinct site for hnRNP C binding proximal to the 5' end of the LI third intron. Cleavage, leading to the production of the small nucleolar RNA U16, occurs in the same position, and we show that conditions under which hnRNP C binding is reduced result in an increase of the processing activity of the intron.
Structure of Xenopus laevis ribosomal protein L32 and its expression during development
Nucleic Acids Research, 1990
cDNA clones for Xenopus laevis ribosomal protein L32 have been isolated and sequenced. The deduced amino acid sequence indicates that L32 is a basic protein of 1 10 amino acids, has a molecular weight of 12,603 and is homologous to the rat ribosomal protein L35. Using the cDNA clone as a probe to follow the expression of this gene during Xenopus development, it has been shown that the pattern of accumulation of this mRNA follows the one previously described for other ribosomal protein mRNAs during oogenesis and embryogenesis. The analysis of the utilization of L32 mRNA during embryogenesis shows that this is controlled by the translational regulation typical of other ribosomal protein mRNAs.
Molecular & general genetics : MGG, 1992
Ribosomal protein synthesis is regulated by controlling the fraction of mRNA associated with polysomes. It is known that this value changes in different developmental stages during Xenopus embryogenesis or, more generally, with changing cell growth conditions. We present here an analysis of the proportion of mRNA loaded on polysomes, carried out with probes for five different ribosomal proteins on several batches of Xenopus embryos obtained from different individuals. The results obtained indicate the existence of probe-dependent and individual differences, which reflect genetic variations in the cis- and trans-acting regulatory elements responsible for translational regulation. The fraction of ribosomal protein mRNA loaded onto polysomes can be used as an index of an individual's capacity for ribosome production.
Molecular and cellular biology, 1990
During Xenopus development, the synthesis of ribosomal proteins is regulated at the translational level. To identify the region of the ribosomal protein mRNAs responsible for their typical translational behavior, we constructed a fused gene in which the upstream sequences (promoter) and the 5' untranslated sequence (first exon) of the gene coding for Xenopus ribosomal protein S19 were joined to the coding portion of the procaryotic chloramphenicol acetyltransferase (CAT) gene deleted of its own 5' untranslated region. This fused gene was introduced in vivo by microinjection into Xenopus fertilized eggs, and its activity was monitored during embryogenesis. By analyzing the pattern of appearance of CAT activity and the distribution of the S19-CAT mRNA between polysomes and messenger ribonucleoproteins, it was concluded that the 35-nucleotide-long 5' untranslated region of the S19 mRNA is able to confer to the fused S19-CAT mRNA the translational behavior typical of ribosom...
Journal of Molecular Biology, 1969
Polyacrylamide gel electrophoresis was used to analyse the rapidly labelled RNA in Xenopus Levis cultured kidney cells. The ribosomal precursor was identified by its base composition and found to have a molecular weight of 2.5 to 2.6 x 106. This is O-3 to 0.4 x lo6 greater than the sum of the weights of the ribosomal RNA. This excess of non-ribosomal RNA has a high content of G+C and is assumed to be lost during processing. The precursor in plant tissues was shown to be similar to that in Xenqnus. A relatively long-lived intermediate in the processing was found in Xenopus and plants, which had a molecular weight of 0.1 x lo6 greater than the heavy ribosomal RNA; it was assumed to be a precursor to the latter. These amounts of excess non-ribosomal RNA are much smaller than in the mammalian 45 and 32 s precursors. It is concluded that the very high molecular weight precursors which contain about 40% of excess RNA are peculiar to the mammals. The results are correlated with other work on the ribosomal DNA and on the structures of the nucleolar core.
Activation of ribosomal RNA genes in preimplantation cattle and swine embryos
Animal Reproduction Science, 2000
. Transcription of ribosomal RNA rRNA genes occurs in the nucleolus resulting in ribosome synthesis. In cattle and swine embryos, functional ribosome-synthesizing nucleoli become structurally recognizable towards the end of the fourth and third post-fertilization cell cycle, respectively. In cattle, a range of important nucleolar proteins become localized to the nucleolar anlage over several cell cycles and this localization is apparently completed towards the end of the fourth cell cycle. In swine, the localization of these proteins to the anlage is more synchronous and occurs towards the end of the third cell cycle and is apparently completed at the onset of the fourth. ) Corresponding author. Tel.: q45-3528-2541; fax: q45-3528-2547. Ž . E-mail address: poh@kvl.dk P. Hyttel . 0378-4320r00r$ -see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 3 7 8 -4 3 2 0 0 0 0 0 0 8 7 -7 ( ) P. Hyttel et al.r Animal Reproduction Science 60-61 2000 49-60 50
The EMBO journal, 1987
A specific control regulates, at the level of RNA splicing, the expression of the L1 ribosomal protein gene in Xenopus laevis. Under particular conditions, which can be summarized as an excess of free L1 protein, a precursor RNA which still contains two of the nine introns of the L1 gene accumulates. In addition to the splicing block the two intron regions undergo specific endonucleolytic cleavages which produce abortive truncated molecules. The accumulation of mature L1 RNA therefore results from the regulation of the nuclear stability of its precursor RNA. We propose that a block to splicing can permit the attack of specific intron regions by nucleases which destabilize the pre-mRNA in the nucleus. Therefore the efficiency of splicing could indirectly control the stability of the pre-mRNA.