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Dynamics and Cell-Type Specificity of the DNA Double-Strand Break Repair Protein RecN in the Developmental Cyanobacterium Anabaena sp. Strain PCC 7120.

Hu S, Wang J, Wang L, Zhang CC, Chen WL - PLoS ONE (2015)

Bottom Line: Treatment by a drug causing DNA double-strand breaks (DSBs) induced reorganization of the RecN focus preferentially towards the mid-cell position.RecN-GFP was absent in most mature heterocysts.Furthermore, our results showed that HetR, a central player in heterocyst development, was involved in the proper positioning and distribution of RecN-GFP.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, 430070 Wuhan, China.

ABSTRACT
DNA replication and repair are two fundamental processes required in life proliferation and cellular defense and some common proteins are involved in both processes. The filamentous cyanobacterium Anabaena sp. strain PCC 7120 is capable of forming heterocysts for N2 fixation in the absence of a combined-nitrogen source. This developmental process is intimately linked to cell cycle control. In this study, we investigated the localization of the DNA double-strand break repair protein RecN during key cellular events, such as chromosome damaging, cell division, and heterocyst differentiation. Treatment by a drug causing DNA double-strand breaks (DSBs) induced reorganization of the RecN focus preferentially towards the mid-cell position. RecN-GFP was absent in most mature heterocysts. Furthermore, our results showed that HetR, a central player in heterocyst development, was involved in the proper positioning and distribution of RecN-GFP. These results showed the dynamics of RecN in DSB repair and suggested a differential regulation of DNA DSB repair in vegetative cell and heterocysts. The absence of RecN in mature heterocysts is compatible with the terminal nature of these cells.

No MeSH data available.


Related in: MedlinePlus

RecN forms a single discrete globular focus in vegetative cells.(A) The three types of vegetative cells divided according to the cell division stages. (B) Localization of RecN-GFP was determined according to its relative position along the x axis and y axis. (C). The locations of the foci in the three types of vegetative cells. The coordinate 0 is the center of the cell. (D) The distributions (in percentage) of the three types of vegetative cells at the relative position of the X-axis. The dynamic localization of RecN-GFP foci was observed with an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Scale bars correspond to 1 μm.
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pone.0139362.g001: RecN forms a single discrete globular focus in vegetative cells.(A) The three types of vegetative cells divided according to the cell division stages. (B) Localization of RecN-GFP was determined according to its relative position along the x axis and y axis. (C). The locations of the foci in the three types of vegetative cells. The coordinate 0 is the center of the cell. (D) The distributions (in percentage) of the three types of vegetative cells at the relative position of the X-axis. The dynamic localization of RecN-GFP foci was observed with an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Scale bars correspond to 1 μm.

Mentions: To perform the subcellular localization of the DNA DSB repair protein RecN, we constructed a strain (RG-W) harboring a recN-gfp gene fusion with a replicative plasmid in the wild-type Anabaena. We compared the expression levels of the wild-type RecN and RecN-GFP by western blotting and determined their relative amounts (S1 Fig). RG-W grows and forms heterocysts like the wild type (data not shown). RecN-GFP displays a single discrete globular focus in most cells (Fig 1A). To better understand the regulation of RecN localization, we divided all cells into three groups according to the division stages. Type 1 cells are at the interphase of cell division; Type 2 cells are divided at the beginning of cell constriction; Type 3 cells are at the end of the division when the cell plate (constricting septum) is formed. We analyzed the relative positions of foci in different cell types as visualized by fluorescence microscopy (Fig 1B). The distribution patterns of Type 1 and Type 3 cells at the relative position of the X-axis and the Y-axis appeared to be random, while Type 2 cells are more likely near the center of the cells (Fig 1C and 1D). Thus, RecN appears to localize as a discrete focus randomly within cells during the interphase of cell division, but it is close to the division center between daughter cells.


Dynamics and Cell-Type Specificity of the DNA Double-Strand Break Repair Protein RecN in the Developmental Cyanobacterium Anabaena sp. Strain PCC 7120.

Hu S, Wang J, Wang L, Zhang CC, Chen WL - PLoS ONE (2015)

RecN forms a single discrete globular focus in vegetative cells.(A) The three types of vegetative cells divided according to the cell division stages. (B) Localization of RecN-GFP was determined according to its relative position along the x axis and y axis. (C). The locations of the foci in the three types of vegetative cells. The coordinate 0 is the center of the cell. (D) The distributions (in percentage) of the three types of vegetative cells at the relative position of the X-axis. The dynamic localization of RecN-GFP foci was observed with an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Scale bars correspond to 1 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4592062&req=5

pone.0139362.g001: RecN forms a single discrete globular focus in vegetative cells.(A) The three types of vegetative cells divided according to the cell division stages. (B) Localization of RecN-GFP was determined according to its relative position along the x axis and y axis. (C). The locations of the foci in the three types of vegetative cells. The coordinate 0 is the center of the cell. (D) The distributions (in percentage) of the three types of vegetative cells at the relative position of the X-axis. The dynamic localization of RecN-GFP foci was observed with an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Scale bars correspond to 1 μm.
Mentions: To perform the subcellular localization of the DNA DSB repair protein RecN, we constructed a strain (RG-W) harboring a recN-gfp gene fusion with a replicative plasmid in the wild-type Anabaena. We compared the expression levels of the wild-type RecN and RecN-GFP by western blotting and determined their relative amounts (S1 Fig). RG-W grows and forms heterocysts like the wild type (data not shown). RecN-GFP displays a single discrete globular focus in most cells (Fig 1A). To better understand the regulation of RecN localization, we divided all cells into three groups according to the division stages. Type 1 cells are at the interphase of cell division; Type 2 cells are divided at the beginning of cell constriction; Type 3 cells are at the end of the division when the cell plate (constricting septum) is formed. We analyzed the relative positions of foci in different cell types as visualized by fluorescence microscopy (Fig 1B). The distribution patterns of Type 1 and Type 3 cells at the relative position of the X-axis and the Y-axis appeared to be random, while Type 2 cells are more likely near the center of the cells (Fig 1C and 1D). Thus, RecN appears to localize as a discrete focus randomly within cells during the interphase of cell division, but it is close to the division center between daughter cells.

Bottom Line: Treatment by a drug causing DNA double-strand breaks (DSBs) induced reorganization of the RecN focus preferentially towards the mid-cell position.RecN-GFP was absent in most mature heterocysts.Furthermore, our results showed that HetR, a central player in heterocyst development, was involved in the proper positioning and distribution of RecN-GFP.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, 430070 Wuhan, China.

ABSTRACT
DNA replication and repair are two fundamental processes required in life proliferation and cellular defense and some common proteins are involved in both processes. The filamentous cyanobacterium Anabaena sp. strain PCC 7120 is capable of forming heterocysts for N2 fixation in the absence of a combined-nitrogen source. This developmental process is intimately linked to cell cycle control. In this study, we investigated the localization of the DNA double-strand break repair protein RecN during key cellular events, such as chromosome damaging, cell division, and heterocyst differentiation. Treatment by a drug causing DNA double-strand breaks (DSBs) induced reorganization of the RecN focus preferentially towards the mid-cell position. RecN-GFP was absent in most mature heterocysts. Furthermore, our results showed that HetR, a central player in heterocyst development, was involved in the proper positioning and distribution of RecN-GFP. These results showed the dynamics of RecN in DSB repair and suggested a differential regulation of DNA DSB repair in vegetative cell and heterocysts. The absence of RecN in mature heterocysts is compatible with the terminal nature of these cells.

No MeSH data available.


Related in: MedlinePlus