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Exploring cellular memory molecules marking competent and active transcriptions.

Xin L, Zhou GL, Song W, Wu XS, Wei GH, Hao DL, Lv X, Liu DP, Liang CC - BMC Mol. Biol. (2007)

Bottom Line: In cells arrested in mitosis, the erythroid-specific activator NF-E2p45 remained associated with its binding sites on the globin gene loci, while the other major erythroid factor, GATA-1, was removed from chromosome.Further analysis showed that other active genes are also locally marked by the preserved active histone code throughout mitotic inactivation of transcription.Our results imply that certain kinds of specific protein factors and active histone modifications function as cellular memory markers for both competent and active genes during mitosis, and serve as a reactivated core for the resumption of transcription when the cells exit mitosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: From National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China. xlgene@263.net <xlgene@263.net>

ABSTRACT

Background: Development in higher eukaryotes involves programmed gene expression. Cell type-specific gene expression is established during this process and is inherited in succeeding cell cycles. Higher eukaryotes have evolved elegant mechanisms by which committed gene-expression states are transmitted through numerous cell divisions. Previous studies have shown that both DNase I-sensitive sites and the basal transcription factor TFIID remain on silenced mitotic chromosomes, suggesting that certain trans-factors might act as bookmarks, maintaining the information and transmitting it to the next generation.

Results: We used the mouse globin gene clusters as a model system to examine the retention of active information on M-phase chromosomes and its contribution to the persistence of transcriptional competence of these gene clusters in murine erythroleukemia cells. In cells arrested in mitosis, the erythroid-specific activator NF-E2p45 remained associated with its binding sites on the globin gene loci, while the other major erythroid factor, GATA-1, was removed from chromosome. Moreover, despite mitotic chromatin condensation, the distant regulatory regions and promoters of transcriptionally competent globin gene loci are marked by a preserved histone code consisting in active histone modifications such as H3 acetylation, H3-K4 dimethylation and K79 dimethylation. Further analysis showed that other active genes are also locally marked by the preserved active histone code throughout mitotic inactivation of transcription.

Conclusion: Our results imply that certain kinds of specific protein factors and active histone modifications function as cellular memory markers for both competent and active genes during mitosis, and serve as a reactivated core for the resumption of transcription when the cells exit mitosis.

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The occupancies of NF-E2p45 on mouse α-like and β-like globin gene clusters in asynchronous (A) and mitotic (M) MEL cells. A. The schematic presentation of mouse α-like and β-like globin gene clusters. Globin genes are shown in dark rectangle. The DNase I hypersensitive sites-HS26, HS21, HS8 of mouse α-globin locus and HS3, HS2, HS1 of mouse β-globin locus, which are analyzed in ChIP assay, are shown in arrow. B. The relative occupancies of NF-E2p45 at HS sites of globin clusters in A and M cell populations were analyzed after normalizing the DNA amount differences in A and M cell populations through DNA input (In-A and In-M).
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Figure 3: The occupancies of NF-E2p45 on mouse α-like and β-like globin gene clusters in asynchronous (A) and mitotic (M) MEL cells. A. The schematic presentation of mouse α-like and β-like globin gene clusters. Globin genes are shown in dark rectangle. The DNase I hypersensitive sites-HS26, HS21, HS8 of mouse α-globin locus and HS3, HS2, HS1 of mouse β-globin locus, which are analyzed in ChIP assay, are shown in arrow. B. The relative occupancies of NF-E2p45 at HS sites of globin clusters in A and M cell populations were analyzed after normalizing the DNA amount differences in A and M cell populations through DNA input (In-A and In-M).

Mentions: In order to confirm this possibility, we arrested murine erythroleukemia (MEL) cells into mitosis by treating the cells with nocodazole [3]. The mitotic index of cell population after treatment was confirmed to be 92–96% by flow cytometry analysis (Fig 2). The results also showed that a proportion of ~5% mitotic cells, about 50% G0/G1-phase and 45% S-phase cells, respectively, is present in asynchronous MEL cell population (Fig 2). The two cell populations were analysed by ChIP to compare the occupancies of NF-E2p45 on distant hypersensitive sites of two mouse globin gene clusters (Fig 3A). The result showed that NF-E2p45 could be specifically recruited to its binding sites HS26 and HS2 in interphase cells (Fig 3B). In mitotic cells it is still tightly associated with HS26 and HS2 (Fig 3B), indicating that NFE2p45 can be retained on mitotic chromosomes to maintain the hypersensitivity of the localized regulatory regions of two mouse globin gene clusters. Its retention, moreover, marks the transcriptional competence of globin genes during MEL cell division.


Exploring cellular memory molecules marking competent and active transcriptions.

Xin L, Zhou GL, Song W, Wu XS, Wei GH, Hao DL, Lv X, Liu DP, Liang CC - BMC Mol. Biol. (2007)

The occupancies of NF-E2p45 on mouse α-like and β-like globin gene clusters in asynchronous (A) and mitotic (M) MEL cells. A. The schematic presentation of mouse α-like and β-like globin gene clusters. Globin genes are shown in dark rectangle. The DNase I hypersensitive sites-HS26, HS21, HS8 of mouse α-globin locus and HS3, HS2, HS1 of mouse β-globin locus, which are analyzed in ChIP assay, are shown in arrow. B. The relative occupancies of NF-E2p45 at HS sites of globin clusters in A and M cell populations were analyzed after normalizing the DNA amount differences in A and M cell populations through DNA input (In-A and In-M).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1884170&req=5

Figure 3: The occupancies of NF-E2p45 on mouse α-like and β-like globin gene clusters in asynchronous (A) and mitotic (M) MEL cells. A. The schematic presentation of mouse α-like and β-like globin gene clusters. Globin genes are shown in dark rectangle. The DNase I hypersensitive sites-HS26, HS21, HS8 of mouse α-globin locus and HS3, HS2, HS1 of mouse β-globin locus, which are analyzed in ChIP assay, are shown in arrow. B. The relative occupancies of NF-E2p45 at HS sites of globin clusters in A and M cell populations were analyzed after normalizing the DNA amount differences in A and M cell populations through DNA input (In-A and In-M).
Mentions: In order to confirm this possibility, we arrested murine erythroleukemia (MEL) cells into mitosis by treating the cells with nocodazole [3]. The mitotic index of cell population after treatment was confirmed to be 92–96% by flow cytometry analysis (Fig 2). The results also showed that a proportion of ~5% mitotic cells, about 50% G0/G1-phase and 45% S-phase cells, respectively, is present in asynchronous MEL cell population (Fig 2). The two cell populations were analysed by ChIP to compare the occupancies of NF-E2p45 on distant hypersensitive sites of two mouse globin gene clusters (Fig 3A). The result showed that NF-E2p45 could be specifically recruited to its binding sites HS26 and HS2 in interphase cells (Fig 3B). In mitotic cells it is still tightly associated with HS26 and HS2 (Fig 3B), indicating that NFE2p45 can be retained on mitotic chromosomes to maintain the hypersensitivity of the localized regulatory regions of two mouse globin gene clusters. Its retention, moreover, marks the transcriptional competence of globin genes during MEL cell division.

Bottom Line: In cells arrested in mitosis, the erythroid-specific activator NF-E2p45 remained associated with its binding sites on the globin gene loci, while the other major erythroid factor, GATA-1, was removed from chromosome.Further analysis showed that other active genes are also locally marked by the preserved active histone code throughout mitotic inactivation of transcription.Our results imply that certain kinds of specific protein factors and active histone modifications function as cellular memory markers for both competent and active genes during mitosis, and serve as a reactivated core for the resumption of transcription when the cells exit mitosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: From National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China. xlgene@263.net <xlgene@263.net>

ABSTRACT

Background: Development in higher eukaryotes involves programmed gene expression. Cell type-specific gene expression is established during this process and is inherited in succeeding cell cycles. Higher eukaryotes have evolved elegant mechanisms by which committed gene-expression states are transmitted through numerous cell divisions. Previous studies have shown that both DNase I-sensitive sites and the basal transcription factor TFIID remain on silenced mitotic chromosomes, suggesting that certain trans-factors might act as bookmarks, maintaining the information and transmitting it to the next generation.

Results: We used the mouse globin gene clusters as a model system to examine the retention of active information on M-phase chromosomes and its contribution to the persistence of transcriptional competence of these gene clusters in murine erythroleukemia cells. In cells arrested in mitosis, the erythroid-specific activator NF-E2p45 remained associated with its binding sites on the globin gene loci, while the other major erythroid factor, GATA-1, was removed from chromosome. Moreover, despite mitotic chromatin condensation, the distant regulatory regions and promoters of transcriptionally competent globin gene loci are marked by a preserved histone code consisting in active histone modifications such as H3 acetylation, H3-K4 dimethylation and K79 dimethylation. Further analysis showed that other active genes are also locally marked by the preserved active histone code throughout mitotic inactivation of transcription.

Conclusion: Our results imply that certain kinds of specific protein factors and active histone modifications function as cellular memory markers for both competent and active genes during mitosis, and serve as a reactivated core for the resumption of transcription when the cells exit mitosis.

Show MeSH
Related in: MedlinePlus