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      Transcriptional Activity in Diplotene Larch Microsporocytes, with Emphasis on the Diffuse Stage

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          Manuscript provides insights into the biology of long-lived plants, different from Arabidopsis, tomato or grass species that are widely studied. In the European larch the diplotene stage lasts approximately 5 months and it is possible to divide it into several substages and to observe each of them in details. The diplotene stage is a period of intensive microsporocyte growth associated with the synthesis and accumulation of different RNA and proteins. Larch microsporocytes display changes in chromatin morphology during this stage, alternating between 4 short stages of chromatin condensation (contraction) and 5 longer diffusion (relaxation) stages. The occurrence of a diplotene diffusion stage has been observed in many plant species. Interestingly, they have also been observed during spermiogenesis and oogenesis in animals. The aim of this study was to examine whether chromatin relaxation during the diplotene is accompanied by the synthesis and maturation of mRNA. The results reveal a correlation between the diffusion and chromatin decondensation, transcriptional activity. We also found decreasing amount of poly(A) mRNA synthesis in the consecutive diffusion stages. During the early diffusion stages, mRNA is intensively synthesized. In the nuclei large amounts of RNA polymerase II, and high levels of snRNPs were observed. In the late diffusion stages, the synthesized mRNA is not directly subjected to translation but it is stored in the nucleus, and later transported to the cytoplasm and translated. In the last diffusion stage, the level of poly(A) RNA is low, but that of splicing factors is still high. It appears that the mRNA synthesized in early stages is used during the diplotene stage and is not transmitted to dyad and tetrads. In contrast, splicing factors accumulate and are most likely transmitted to the dyad and tetrads, where they are used after the resumption of intense transcription. Similar meiotic process were observed during oogenesis in animals. This indicates the existence of an evolutionarily conserved mechanism of chromatin-based regulation of gene expression during meiotic prophase I.

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          Most cited references 44

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          Differences in the Localization and Morphology of Chromosomes in the Human Nucleus

          Using fluorescence in situ hybridization we show striking differences in nuclear position, chromosome morphology, and interactions with nuclear substructure for human chromosomes 18 and 19. Human chromosome 19 is shown to adopt a more internal position in the nucleus than chromosome 18 and to be more extensively associated with the nuclear matrix. The more peripheral localization of chromosome 18 is established early in the cell cycle and is maintained thereafter. We show that the preferential localization of chromosomes 18 and 19 in the nucleus is reflected in the orientation of translocation chromosomes in the nucleus. Lastly, we show that the inhibition of transcription can have gross, but reversible, effects on chromosome architecture. Our data demonstrate that the distribution of genomic sequences between chromosomes has implications for nuclear structure and we discuss our findings in relation to a model of the human nucleus that is functionally compartmentalized.
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            Small nucleolar RNAs: an abundant group of noncoding RNAs with diverse cellular functions.

             Tamás Kiss (2002)
            Small nucleolar RNAs represent an abundant, evolutionarily ancient group of noncoding RNAs which possess impressively diverse functions ranging from 2'-O-methylation and pseudouridylation of various classes of RNAs, through nucleolytic processing of rRNAs to the synthesis of telomeric DNA.
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              Cajal body-specific small nuclear RNAs: a novel class of 2'-O-methylation and pseudouridylation guide RNAs.

              Cajal (coiled) bodies are conserved subnuclear organelles that are present in the nucleoplasm of both animal and plant cells. Although Cajal bodies were first described nearly 100 years ago, their function has remained largely speculative. Here, we describe a novel class of human small nuclear RNAs that localize specifically to Cajal bodies. The small Cajal body-specific RNAs (scaRNAs) are predicted or have already been demonstrated to function as guide RNAs in site-specific synthesis of 2'-O-ribose-methylated nucleotides and pseudouridines in the RNA polymerase II-transcribed U1, U2, U4 and U5 spliceosomal small nuclear RNAs (snRNAs). Our results provide strong support for the idea that the Cajal body, this mysterious nuclear organelle, provides the cellular locale for post-transcriptional modification of spliceosomal snRNAs.

                Author and article information

                [1 ]Department of Cell Biology, Faculty of Biology and Environment Protection, Nicolaus Copernicus University, Toruń, Poland
                [2 ]Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Toruń, Poland
                International Centre for Genetic Engineering and Biotechnology, ITALY
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: AKL DJS. Performed the experiments: AKL MS DJS. Analyzed the data: AKL JN EBK DJS. Contributed reagents/materials/analysis tools: AKL JN DJS. Wrote the paper: AKL DJS.

                Role: Academic Editor
                PLoS One
                PLoS ONE
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                11 February 2015
                : 10
                : 2

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

                Figures: 4, Tables: 0, Pages: 17
                This work was supported by Polish National Science Center (NCN): no. N 303 799640 and no. of agreement 7796/B/P01/2011/40. Start 2011-06-13, end 2014-06-12. URL: Grant has already finished and there is no money from this resource. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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