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The Chlamydomonas Chloroplast HLP Protein Is Required for nucleoid Organization and Genome Maintenance

Molecular Plant 2009年第6期2卷 1223-1232页

作者： Daniel Karcher Dietrich Koster Anne Schadach Anja Klevesath Ralph Bock Max-Planck-lnstitut fur Molekulare Pflanzenphysiologie Am Muhlenberg 1 D-14476 Potsdam-Golm Germany

The chloroplasts genome （plastome） occurs at high copy numbers per cell. Several chloroplast genome copies are densely packed into nucleoprotein particles called nucleoids. How genome packaging occurs and which proteins organize chloroplast nucleoids are largely unknown. Here, we have analyzed the Chlamydornonas reinhardtii homolog of the bacterial architectural DNA-binding protein HU, the histone-like protein HLP. We show that the Chlarnydornonas HLP protein is targeted to chloroplasts and associates with nucleoids. Knockdown of HLP gene expression by RNA interference （RNAi） alters the structure of chloroplast nucleoids and appears to reduce the level of compaction of chloroplast DNA. Unexpectedly, also chloroplast genome copy numbers are significantly decreased in the RNAi strains, suggesting that, in addition to its architectural role in nucleoid formation, the HIP protein is also involved in chloroplast genome maintenance.

关键词： Chloroplast nucleoid Chlamydomonas reinhardtii HLP DNA-binding protein genome maintenance

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Ring-like nucleoid does not play a key role in radioresistance of Deinococcus radiodurans

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Science China(Life Sciences) 2007年第4期50卷 525-529页

作者： GAO GuanJun, LU HuiMing, YIN LongFei & HUA YueJin Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou 310029, China 1. Institute of Nuclear-Agricultural Sciences Zhejiang University Hangzhou 310029 China

The conclusion based on transmission electron microscopy, "the tightly packed ring-like nucleoid of the Deinococcus radiodurans R1 is a key to radioresistance", has instigated lots of debates. In this study, according to the previous research of PprI’s crucial role in radioresistance of D. radiodurans, we have attempted to examine and compare the nucleoid morphology differences among wild-type D. ra-diodurans R1 strain, pprI function-deficient mutant (YR1), and pprI function-complementary strains (YR1001, YR1002, and YR1004) before and after exposure to ionizing irradiation. Fluorescence mi-croscopy images indicate: (1) the majority of nucleoid structures in radioresistant strain R1 cells ex-hibit the tightly packed ring-like morphology, while the pprI function-deficient mutant YR1 cells carrying predominate ring-like structure represent high sensitivity to irradiation; (2) as an extreme radioresistant strain similar to wild-type R1, pprI completely function-complementary strain YR1001 almost displays the loose and irregular nucleoid morphologies. On the other hand, another radioresistant pprI partly function-complementary strain YR1002’s nucleiods exhibit about 60% ring-like structure; (3) a PprI C-terminal deletion strain YR1004 consisting of approximately 60% of ring-like nucleoid is very sensi-tive to radiation. Therefore, our present experiments do not support the conclusion that the ring-like nucleoid of D. radiodurans does play a key role in radioresistance.

关键词： Deinococcus radiodurans R1 ring-like nucleoid pprI ionizing irradiation radioresistance

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Dps Is a Stationary Phase-Specific Protein of <i>Escherichia coli</i>nucleoid

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Advances in Microbiology 2014年第15期4卷 1095-1104页

作者： Ali Azam Talukder Akira Ishihama Department of Microbiology Jahangirnagar University Savar Bangladesh Department of Molecular Genetics National Institute of Genetics Mishima Japan Micro-Nano Technology Research Center Hosei University Tokyo Japan Japan Science and Technology Corporation Kawaguchi Japan Japan Society for the Promotion of Science Tokyo Japan

Bacterial genomic DNA is highly organized into one or few compacted bodies known as nucleoid, which is composed of DNA, RNA and several DNA-binding proteins. These DNA-binding proteins require essential alterations in their expression during stationary phase of growth in order to re-spond to stressful environmental conditions. Dps (DNA-binding protein from starved cells) is one of such DNA-binding proteins, which accumulates most when E. coli cells reach to the stationary phase. Here, we have characterized Dps protein under various growth phases. Immunofluorescent microscopic observation reveals that Dps plays a key role in final round of genome compaction during the stationary phase. Similar results are also obtained by Western immunoblot analysis, after quantification of Dps protein from the exponential phase and early stationary phase nucleoid bound fractions, separated by sucrose density gradient centrifugation. Our results support the conclusion that Dps occupies more than half of the stationary phase nucleoid in E. coli.

关键词： Dps DNA-Binding Protein Stationary Phase E. coli nucleoid

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Features of Structurization at Participation of Guanidine Groups of Arginine in Life Cycle in Population of E. coil

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Journal of Life Sciences 2013年第1期7卷 8-12页

作者： Tropynina Tatyana Ivanova Evilina Vafina Gulnara Ivanov Ruslan Institute of Biology Ufa Science Centre Russian Academy of Science Ufa 450054 Bashkortostan Russia

The purpose of the given work was the experimental analysis of features of Arg-X proteolysis in proteom of supramolecular structures of bacterial cells during their life cycle. The basic attention was devoted to relaxation of Arg-X sites of proteom in association with the evolutionary significance ofArg-rich histones in the eukaryotic kingdom. These properties were not studied in the prokaryotes. Cells ofE. coli were grown to the stationary phase, collected by centrifugation and washed. All cells were taken over from 50 min to 430 min at intervals of 20 min and were preserved in glycerol. The supramolecular structures were fractionated from bacterial cells by increasing ionic strength of solution. The Arg-Xactivity was assessed by cleavage of Arg-Xbonds in the arginine-enriched protein protamine in all cell fractions. We have shown that during the stationary phase in the life cycle of E. coli, there are a high continuous activity of the Arg-X processing at the level of＂cytoskeleton＂ of the cell and bright cyclic activity in the cytoplasm.

关键词： Arginine Arg-X protease-sensitive supramolecular structures nucleoid E. coli.

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