Nucleosome assembly in mammalian cell extracts before and after DNA replication.

Gruss, Claudia; Gutiérrez, Crisanto; Burhans, William C.; DePamphilis, Melvin L.; Koller, Th.; Sogo, José M.

doi:10.1002/j.1460-2075.1990.tb07482.x

Cited by 64 publications

(50 citation statements)

References 73 publications

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“…In the case of Py, ori-core no longer requires an enhancer when chromatin structure is either absent or altered. The Py enhancer (aux-2) is not required to activate Py on-core in cytoplasmic extracts (73), conditions in which chromatin assembly does not occur (33). Enhancers also are not required to activate either an on-core or a promoter encoded by plasmids injected into the male pronucleus of fertilized mouse eggs (56,57,94), in which repression by chromatin structure is absent (93a).…”

Section: Resultsmentioning

confidence: 99%

Specific transcription factors stimulate simian virus 40 and polyomavirus origins of DNA replication.

Guo¹,

DePamphilis²

1992

Mol. Cell. Biol.

102

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The origins of DNA replication (ori) in simian virus 40 (SV40) and polyomavirus (Py) contain an auxiliary component (aux-2) composed of multiple transcription factor binding sites. To determine whether this component stimulated replication by binding specific transcription factors, aux-2 was replaced by synthetic oligonucleotides that bound a single transcription factor. Spl and T-antigen (T-ag) sites, which exist in the natural SV40 aux-2 sequence, provided -75 and -20%, respectively, of aux-2 activity when transfected into monkey cells. In cell extracts, only T-ag sites were active. AP1 binding sites could replace completely either SV40 or Py aux-2. Mutations that eliminated API binding also eliminated AP1 stimulation of replication. Yeast GAL4 binding sites that strongly stimulated transcription in the presence of GAL4 proteins failed to stimulate SV40 DNA replication, although they did partially replace Py aux-2. Stimulation required the presence of proteins consisting of the GAL4 DNA binding domain fused to specific activation domains such as VP16 or c-Jun. These data demonstrate a clear role for transcription factors with specific activation domains in activating both SV40 and Py ori. However, no correlation was observed between the ability of specific proteins to stimulate promoter activity and their ability to stimulate origin activity. We propose that only transcription factors whose specific activation domains can interact with the T-ag initiation complex can stimulate SV40 and Py ori-core activity.Most, if not all, of the eukaryotic origins of DNA replication (on) characterized so far consist of two principal components: the core component that determines where replication begins in the chromosome and in which animal species replication occurs, and one or more auxiliary components that stimulate replication in certain cell types (28,30,96). on-core is the minimal cis-acting sequence required to initiate DNA replication under all conditions; it is analogous to a transcription promoter. on-auxiliary sequences generally consist of transcription factor binding sites that are dispensable under some conditions; they are analogous to transcription enhancers. The purpose of auxiliary components may be to regulate DNA replication by determining when initiation occurs. For example, the polyomavirus (Py) on functions only in those mouse cell types that can activate its enhancer (6,12,58,74). In mammalian chromosomes, active genes are replicated early during S phase while quiescent genes are replicated late (82), and initiation of replication may require specific transcription factors (76) that bind DNA sites where replication begins (11).To elucidate the function of on-auxiliary components in mammals, we turned our attention to the origins of DNA replication in simian virus 40 (SV40) and Py. These two closely related viral chromosomes replicate in the nuclei of mammalian cells and, with the exception of a single viral protein (large tumor antigen [T-ag]), rely entirely on the host to replicate their DNA (13,29)....

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Section: Resultsmentioning

confidence: 99%

Specific transcription factors stimulate simian virus 40 and polyomavirus origins of DNA replication.

Guo¹,

DePamphilis²

1992

Mol. Cell. Biol.

102

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“…It is now well recognized that a plasmid containing the SV40 promoter (origin)/enhancer elements can be assembled into the chromatin structure following the transfection of CV-1 or COS cells (35,36). Such nucleosomal assembly indicates that plasmid DNA replication and transcription closely resembles SV40…”

Section: Discussionmentioning

confidence: 99%

A Novel Role for RAX, the Cellular Activator of PKR, in Synergistically Stimulating SV40 Large T Antigen-dependent Gene Expression

Yang

Ito²,

May

2003

Journal of Biological Chemistry

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The double-stranded (ds) RNA-binding protein RAX was discovered as a stress-induced cellular activator of the dsRNA-dependent protein kinase (PKR), a key regulator of protein synthesis in response to viral infection and cellular stress. We now report a novel function of RAX, independent of PKR, to enhance SV40 promoter (origin)/enhancer-dependent gene expression. Several mammalian cell lines including COS-7, CV-1, and HeLa cells were tested. Results reveal that the SV40 large T antigen is required for RAX-mediated, synergistic enhancement of gene expression. RAX augments SV40 regulatory element-dependent DNA replication and transcription. The mechanism requires the SV40 enhancer, a viral transcriptional element that is necessary for efficient SV40 DNA replication in vivo. Mutational analysis reveals that the dsRNA-binding domains of RAX are required for the gene expression enhancing function. Thus, in addition to stimulating PKR activity, RAX can positively regulate both SV40 large T antigen-dependent DNA replication and transcription in a mechanism that may alter the interaction of the cellular factor(s) with the SV40 enhancer via the dsRNA-binding domains of RAX. This novel function of RAX may have implications for regulation of mammalian DNA replication and transcription because of the many similarities between the viral and cellular processes.

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“…Histones and transcription factors were found to compete for association with the 5S rRNA gene, yet the first histones to associate with the 5S rRNA genes during chromatin assembly were less repressive toward transcription. Chromatin assembly in vivo and in vitro is optimally coupled to replication (Worcel et al 1978;Almouzni et al 1991;Gruss et al 1990) such that an acetylated histone tetramer (H3/H4)2 is sequestered before H2A/H2B and, finally, HI. This creates a window of opportunity for the programming of the 5S rRNA genes with transcription factors, because the (H3/H4)2 tetramer is less repressive than the complete (H2A/H2B, H3/H4)2 octamer, whereas chromatin containing histone H1 is essentially inert and inaccessible to the class III gene transcriptional machinery.…”

Section: Histone H1 and The Selective Repression Of The Oocyte 5s Rrnmentioning

confidence: 99%

Specific regulation of Xenopus chromosomal 5S rRNA gene transcription in vivo by histone H1.

Bouvet

Dimitrov²,

Wolffe³

1994

Genes Dev.

233

154

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The incorporation of histone H1 into chromatin during embryogenesis directs the specific repression of the Xenopus oocyte 5S rRNA genes. An increase in histone H1 content specifically restricts TFIIIA-activated transcription, and a decrease in histone HI within chromatin facilitates the activation of the oocyte 5S rRNA genes by TFIIIA. Variation in the amount of histone HI in chromatin does not significantly influence somatic 5S rRNA gene transcription. Thus, the regulated expression of histone HI during Xenopus development has a specific and dominant role in mediating the differential expression of the oocyte and somatic 5S rRNA genes. This example demonstrates that histones can exert dominant repressive effects on the transcription of a gene in vivo in spite of an abundance of transcription factors for that gene.

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Nucleosome assembly in mammalian cell extracts before and after DNA replication.

Cited by 64 publications

References 73 publications

Specific transcription factors stimulate simian virus 40 and polyomavirus origins of DNA replication.

Specific transcription factors stimulate simian virus 40 and polyomavirus origins of DNA replication.

A Novel Role for RAX, the Cellular Activator of PKR, in Synergistically Stimulating SV40 Large T Antigen-dependent Gene Expression

Specific regulation of Xenopus chromosomal 5S rRNA gene transcription in vivo by histone H1.

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