VIOQUE PEÑA , Agustín

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The genes encoding the RNA subunit of ribonuclease P from the unicellular cyanobacterium Synechocystis sp. PCC 6803, and from the heterocyst-forming strains Anabaena sp. PCC 7120 and Calothrix sp. PCC 7601 were cloned using the homologous gene from Anacystis nidulans (Synechococcus sp. PCC 6301) as a probe. The genes and the flanking regions...

M1 RNA, the catalytic subunit of Escherichia coli RNase P, has been covalently linked at its 3' terminus to agarose beads. Unlike M1 RNA, which is active in solution in the absence of the protein component (C5) of RNase P, the RNA linked to the beads is active only in the presence of C5 protein. Affinity chromatography of crude extracts of E....

We have studied the effect of the 3′ terminal CCA sequence in precursors of tRNAs on catalysis by the RNase P RNA or the holoenzyme from the cyanobacterium Synechocystis sp. PCC 6803 in a completely homologous system. We have found that the absence of the 3′ terminal CCA is not detrimental to activity, which is in sharp contrast to what is...

Hfq is an RNA binding protein involved in posttranscriptional regulation of gene expression in bacteria. It acts by binding to regulatory small RNAs (sRNAs), which confer specificity for the regulation. Recently, orthologues of the Hfq protein were annotated in cyanobacterial genomes, although its capacity to regulate gene expression by...

Biosynthesis of transfer RNA requires processing from longer precursors at the 5′- and 3′-ends. In eukaryotes, in archaea, and in those bacteria where the 3′-terminal CCA sequence is not encoded, 3′ processing is carried out by the endonuclease RNase Z, which cleaves after the discriminator nucleotide to generate a mature 3′-end ready for the...

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tmRNA (also known as SsrA or 10Sa RNA) is involved in a trans-translation reaction that contributes to the recycling of stalled ribosomes at the 3′ end of an mRNA lacking a stop codon or at an internal mRNA cluster of rare codons. Inactivation of the ssrA gene in most bacteria results in viable cells bearing subtle phenotypes, such as...

The RNase P RNA catalytic subunit (RPR) encoded in some plastids has been found to be functionally defective. The amoeba Paulinella chromatophora contains an organelle (chromatophore) that is derived from the recent endosymbiotic acquisition of a cyanobacterium, and therefore represents a model of the early steps in the acquisition of plastids....

We have isolated, based on the knowledge of the complete genomic sequence of the cyanobacterium Synechocystis sp. PCC 6803, an open reading frame (slr0088) similar to known bacterial carotene desaturases and have analyzed the function of the encoded protein. Surprisingly, this protein has no detectable desaturase activity with phytoene,...

We have constructed a strain (CT1) that expresses RNase P conditionally with the aim to analyze the in vivotRNA processing pathway and the biological role that RNase P plays inSynechocystis 6803. In this strain, the rnpBgene, coding for the RNA subunit of RNase P, has been placed under the control of the petJ gene promoter (PpetJ), which is...

Heterocystous cyanobacteria such as Nostoc sp. are filamentous photosynthetic organisms that, in response to nitrogen deficiency, undergo a differentiation process transforming certain, semi-regularly spaced cells into heterocysts, devoted to nitrogen fixation. During transition to a nitrogen-fixing regime, growth of most vegetative cells in...

Yfr1 is a strictly conserved small RNA in cyanobacteria. A bioinformatic prediction to identify possible interactions of Yfr1 with mRNAs was carried out by using the sequences of Yfr1 from several heterocyst-forming strains, including Nostoc sp. strain PCC 7120. The results of the prediction were enriched in genes encoding outer membrane...

Small regulatory RNAs (sRNAs) are currently considered as major post-transcriptional regulators of gene expression in bacteria. The interplay between sRNAs and transcription factors leads to complex regulatory networks in which both transcription factors and sRNAs may appear as nodes. In cyanobacteria, the responses to nitrogen availability are...

Transcriptomic analyses using high-throughput methods have revealed abundant antisense transcription in bacteria. Antisense transcription is often due to the overlap of mRNAs with long 5′ or 3′ regions that extend beyond the coding sequence. In addition, antisense RNAs that do not contain any coding sequence are also observed. Nostoc sp. PCC...

For an enzyme functioning predominantly in a seemingly housekeeping role of 5′ tRNA maturation, RNase P displays a remarkable diversity in subunit make-up across the three domains of life. Despite the protein complexity of this ribonucleoprotein enzyme increasing dramatically from bacteria to eukarya, the catalytic function rests with the RNA...

Upon nitrogen starvation, filamentous cyanobacteria develop heterocysts, specialized cells devoted to the fixation of atmospheric nitrogen. Differentiation of heterocyst at semi-regular intervals along the filaments requires complex structural and functional changes that are under the control of the master transcriptional regulator HetR. NsiR1...

The fixation of atmospheric N2 by cyanobacteria is a major source of nitrogen in the biosphere. In Nostocales, such as Anabaena, this process is spatially separated from oxygenic photosynthesis and occurs in heterocysts. Upon nitrogen step-down, these specialized cells differentiate from vegetative cells in a process controlled by two major...