The factors involved in rRNA processing in eukaryotes assemble cotranscriptionally onto the nascent prerRNAs and include endonucleases, exonucleases, RNA helicases, GTPases, modifying enzymes and snoRNPs (small nucleolar ribonucleoproteins). The precursor of three of the four eukaryotic mature rRNAs contains the rRNA sequences flanked by two internal (ITS1 and ITS2) and two external (5¢-ETS and 3¢-ETS) spacer sequences that are removed during processing [1,2]. The pre-rRNA is first assembled into a 90S particle that contains U3 snoRNP and 40S subunit-processing factors [3,4]. The early pre-rRNA endonucleolytic cleavages at sites A 0 , A 1 and A 2 occur within the 90S particles [3,5]. A 2 cleavage releases the first pre60S particle, which differs in composition from the known 90S particle. Pre60S particles contain 27S rRNA, ribosomal L proteins and many nonribosomal proteins [6].As they mature, pre60S particles migrate from the nucleolus to the nucleoplasm and their content of nonribosomal factors changes [7,8]. Nip7p was among the proteins identified in the early pre60S particle [6][7][8], and has been shown to participate in the processing of 27S pre-rRNA to the formation of 25S [9]. Interestingly, Nip7p also binds the exosome subunit Rrp43p [10]. The exosome complex is responsible for the degradation of the excised 5¢-ETS and for the 3¢)5¢ exonucleolytic processing of 7S pre-rRNA to form the mature 5.8S rRNA. The exosome is also involved in the processing of snoRNAs and in mRNA degradation [11][12][13].During processing, pre-rRNA undergoes covalent modifications that include isomerization of some uridines into pseudouridines and addition of methyl groups to specific nucleotides, mainly at the 2¢-O posi- In eukaryotes, pre-rRNA processing depends on a large number of nonribosomal trans-acting factors that form large and intriguingly organized complexes. A novel nucleolar protein, Nop53p, was isolated by using Nop17p as bait in the yeast two-hybrid system. Nop53p also interacts with a second nucleolar protein, Nip7p. A carbon source-conditional strain with the NOP53 coding sequence under the control of the GAL1 promoter did not grow in glucose-containing medium, showing the phenotype of an essential gene. Under nonpermissive conditions, the conditional mutant strain showed rRNA biosynthesis defects, leading to an accumulation of the 27S and 7S pre-rRNAs and depletion of the mature 25S and 5.8S mature rRNAs. Nop53p did not interact with any of the exosome subunits in the yeast twohybrid system, but its depletion affects the exosome function. In pull-down assays, protein A-tagged Nop53p coprecipitated the 27S and 7S pre-rRNAs, and His-Nop53p also bound directly 5.8S rRNA in vitro, which is consistent with a role for Nop53p in pre-rRNA processing.Abbreviations ETS, external transcribed spacer; b-Gal, b-galactosidase; GFP, green fluorescent protein; GST, glutathione S-transferase; ITS, internal transcribed spacer; RFP, red fluorescent protein; snoRNP, small nucleolar ribonucleoprotein.
Resumo A previsão da data de floração da soja é importante para o manejo da cultura e para o uso em modelos de crescimento e de produção. O objetivo deste estudo foi o de quantificar o efeito do fotoperíodo e da temperatura na duração do período de florescimento, e avaliar a resposta de um modelo linear simples para predizer o período de floração de genótipos de soja de diferentes grupos de maturação, em diferentes épocas. Foi avaliada a habilidade da equação D = a + b T + c F, onde a , b e c são parâmetros empíricos, e T e F representam a média da temperatura e do fotoperíodo entre a emergência e a floração. Os parâmetros no modelo foram avaliados mediante análise de regressão múltipla, combinando os dados de dois anos agrícolas, em Passo Fundo, RS, em relação a cada genótipo. O período entre a emergência e o florescimento foi afetado pela temperatura e pelo fotoperíodo. As cultivares e a linhagem apresentaram diferentes sensibilidades a cada um desses fatores, resultando em coeficientes distintos. As datas de floração estimadas e observadas foram altamente significativas (r 2 superiores a 0,77) em todos os genótipos, com uma variação de erro-padrão entre 2,4 e 4,8 dias.Termos para indexação: Glycine max, floração, fatores ambientais, época de semeadura. Quantitative response of soybean flowering to temperature and photoperiodAbstract Predicting the time of soybean flowering is a critical step for crop management practices, as well as for the development of crop models. The objective of this study was to quantify the effect of photoperiod and of temperature on the duration of the flowering period, and to evaluate the response of a simple linear model for predicting the flowering period of soybean genotypes of different maturation groups within different epochs. The ability of the equation D = a + b T + c F, where a , b and c are empirical parameters, and T and F refer to the medium temperature and to the photoperiod between emergence and flowering, was evaluated. Evaluation of the coefficients were carried out through multiple regression analysis combining the data sets from two growing seasons for each genotype (1995/96 and 1996/97) in Passo Fundo, RS, Brazil. Multiple regression analysis showed that the period between emergence and flowering was influenced by temperature and photoperiod. The cultivars under study showed different susceptibilities to each factor, resulting in specific coefficients. The agreement between observed and predicted time of flowering was highly significant for all genotypes (r 2 higher than 0.77) with standard deviations ranging from 2.4 and 4.8 days.Index terms: Glycine max, flowering, environmental factors, sowing date.(1) Aceito para publicação em 2 de junho de 2000. Introdução Fotoperíodo e temperatura são importantes para o desenvolvimento da cultura da soja, por provocarem mudanças qualitativas ao longo do seu ciclo. As respostas a esses dois fatores não são lineares durante o ciclo de vida da cultura, pois existem
The conserved protein Nip7 is involved in ribosome biogenesis, being required for proper 27S pre-rRNA processing and 60S ribosome subunit assembly in Saccharomyces cerevisiae. Yeast Nip7p interacts with nucleolar proteins and with the exosome subunit Rrp43p, but its molecular function remains to be determined. Solution of the Pyrococcus abyssi Nip7 (PaNip7) crystal structure revealed a monomeric protein composed by two alpha-beta domains. The N-terminal domain is formed by a five-stranded antiparallel beta-sheet surrounded by three alpha-helices and a 310 helix while the C-terminal, a mixed beta-sheet domain composed by strands beta8 to beta12, one alpha-helix, and a 310 helix, corresponds to the conserved PUA domain (after Pseudo-Uridine synthases and Archaeosine-specific transglycosylases). By combining structural analyses and RNA interaction assays, we assessed the ability of both yeast and archaeal Nip7 orthologues to interact with RNA. Structural alignment of the PaNip7 PUA domain with the RNA-interacting surface of the ArcTGT (archaeosine tRNA-guanine transglycosylase) PUA domain indicated that in the archaeal PUA domain positively charged residues (R151, R152, K155, and K158) are involved in RNA interaction. However, equivalent positions are occupied by mostly hydrophobic residues (A/G160, I161, F164, and A167) in eukaryotic Nip7 orthologues. Both proteins can bind specifically to polyuridine, and RNA interaction requires specific residues of the PUA domain as determined by site-directed mutagenesis. This work provides experimental verification that the PUA domain mediates Nip7 interaction with RNA and reveals that the preference for interaction with polyuridine sequences is conserved in Archaea and eukaryotic Nip7 proteins.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.