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Co-transcriptional nuclear actin dynamics.

Percipalle P - Nucleus (2012)

Bottom Line: This high degree of promiscuity in the spectrum of protein-to-protein interactions correlates well with the conformational plasticity of actin and the ability to undergo regulated changes in its polymerization states.Several of the factors involved in controlling head-to-tail actin polymerization have been shown to be in the nucleus where they seem to regulate gene activity.By focusing on the multiple tasks performed by actin and actin-binding proteins, possible models of how actin dynamics controls the different phases of the RNA polymerase II transcription cycle are being identified.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden. piergiorgio.percipalle@ki.se

ABSTRACT
Actin is a key player for nuclear structure and function regulating both chromosome organization and gene activity. In the cell nucleus actin interacts with many different proteins. Among these proteins several studies have identified classical nuclear factors involved in chromatin structure and function, transcription and RNA processing as well as proteins that are normally involved in controlling the actin cytoskeleton. These discoveries have raised the possibility that nuclear actin performs its multi task activities through tight interactions with different sets of proteins. This high degree of promiscuity in the spectrum of protein-to-protein interactions correlates well with the conformational plasticity of actin and the ability to undergo regulated changes in its polymerization states. Several of the factors involved in controlling head-to-tail actin polymerization have been shown to be in the nucleus where they seem to regulate gene activity. By focusing on the multiple tasks performed by actin and actin-binding proteins, possible models of how actin dynamics controls the different phases of the RNA polymerase II transcription cycle are being identified.

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Figure 3. A schematic diagram summarizing the RNA polymerase II transcription cycle. Actin is known to be directly involved in PIC formation, escape from pausing and transcription elongation.
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Figure 3: Figure 3. A schematic diagram summarizing the RNA polymerase II transcription cycle. Actin is known to be directly involved in PIC formation, escape from pausing and transcription elongation.

Mentions: Based on the above considerations, one would expect that actin is preferentially coupled to transcriptionally active genes. Several observations support this hypothesis. First, as already mentioned, actin association with chromatin is RNA-dependent both in C. tentans and in mammals.27,29 Furthermore, actin does not occupy untranslated regions (UTRs) and flanking regions of RNA polymerase II genes,40 its nuclear distribution depends on the transcriptional activity of the cell41 and own unpublished evidence indicates that actin occupancy is considerably reduced in intergenic regions separating consecutive rDNA transcription units. Whether actin association with the gene is transcription dependent or not still remains controversial due to a study where chromatin immunoprecipitations showed actin binding to chromatin isolated from actinomycin D-treated cells and thus, transcriptionally silent.42 Chromatin immunoprecipitations rely on different chromatin preparations and actin antibodies.27,29,40-42 In any case, the idea that actin preferentially occupies transcriptionally active chromatin is corroborated by an independent recent work where in Drosophila, chromatin was systematically mapped to five principal types and actin exclusively associates with transcriptionally competent euchromatin.43 We conclude that during the RNA polymerase II transcription cycle actin is directly involved in PIC formation, escape from pausing and transcription elongation (Fig. 3).


Co-transcriptional nuclear actin dynamics.

Percipalle P - Nucleus (2012)

Figure 3. A schematic diagram summarizing the RNA polymerase II transcription cycle. Actin is known to be directly involved in PIC formation, escape from pausing and transcription elongation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3585027&req=5

Figure 3: Figure 3. A schematic diagram summarizing the RNA polymerase II transcription cycle. Actin is known to be directly involved in PIC formation, escape from pausing and transcription elongation.
Mentions: Based on the above considerations, one would expect that actin is preferentially coupled to transcriptionally active genes. Several observations support this hypothesis. First, as already mentioned, actin association with chromatin is RNA-dependent both in C. tentans and in mammals.27,29 Furthermore, actin does not occupy untranslated regions (UTRs) and flanking regions of RNA polymerase II genes,40 its nuclear distribution depends on the transcriptional activity of the cell41 and own unpublished evidence indicates that actin occupancy is considerably reduced in intergenic regions separating consecutive rDNA transcription units. Whether actin association with the gene is transcription dependent or not still remains controversial due to a study where chromatin immunoprecipitations showed actin binding to chromatin isolated from actinomycin D-treated cells and thus, transcriptionally silent.42 Chromatin immunoprecipitations rely on different chromatin preparations and actin antibodies.27,29,40-42 In any case, the idea that actin preferentially occupies transcriptionally active chromatin is corroborated by an independent recent work where in Drosophila, chromatin was systematically mapped to five principal types and actin exclusively associates with transcriptionally competent euchromatin.43 We conclude that during the RNA polymerase II transcription cycle actin is directly involved in PIC formation, escape from pausing and transcription elongation (Fig. 3).

Bottom Line: This high degree of promiscuity in the spectrum of protein-to-protein interactions correlates well with the conformational plasticity of actin and the ability to undergo regulated changes in its polymerization states.Several of the factors involved in controlling head-to-tail actin polymerization have been shown to be in the nucleus where they seem to regulate gene activity.By focusing on the multiple tasks performed by actin and actin-binding proteins, possible models of how actin dynamics controls the different phases of the RNA polymerase II transcription cycle are being identified.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden. piergiorgio.percipalle@ki.se

ABSTRACT
Actin is a key player for nuclear structure and function regulating both chromosome organization and gene activity. In the cell nucleus actin interacts with many different proteins. Among these proteins several studies have identified classical nuclear factors involved in chromatin structure and function, transcription and RNA processing as well as proteins that are normally involved in controlling the actin cytoskeleton. These discoveries have raised the possibility that nuclear actin performs its multi task activities through tight interactions with different sets of proteins. This high degree of promiscuity in the spectrum of protein-to-protein interactions correlates well with the conformational plasticity of actin and the ability to undergo regulated changes in its polymerization states. Several of the factors involved in controlling head-to-tail actin polymerization have been shown to be in the nucleus where they seem to regulate gene activity. By focusing on the multiple tasks performed by actin and actin-binding proteins, possible models of how actin dynamics controls the different phases of the RNA polymerase II transcription cycle are being identified.

Show MeSH