scholarly journals As functional nuclear actin comes into view, is it globular, filamentous, or both?

2008 ◽  
Vol 180 (6) ◽  
pp. 1061-1064 ◽  
Author(s):  
Thoru Pederson
Keyword(s):  
Signal Transduction ◽  
Rna Polymerase ◽  
Research Field ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Nuclear Actin ◽  
Structural Form ◽  
Rapid Transition ◽  
Polymerase I ◽  
Polymeric Actin

The idea that actin may have an important function in the nucleus has undergone a rapid transition from one greeted with skepticism to a now rapidly advancing research field. Actin has now been implicated in transcription by all three RNA polymerases, but the structural form it adopts in these processes remains unclear. Recently, a claim was made that monomeric nuclear actin plays a role in signal transduction, while a just-published study of RNA polymerase I transcription has implicated polymeric actin, consorting with an isoform of its classical partner myosin. Both studies are critically discussed here, and although there are several issues to be resolved, it now seems reasonable to start thinking about functions for both monomeric and assembled actin in the nucleus.

Actin dynamics and functions in the interphase nucleus: moving toward an understanding of nuclear polymeric actinThis paper is one of a selection of papers published in this Special Issue, entitled 29th Annual International Asilomar Chromatin and Chromosomes Conference, and has undergone the Journal’s usual peer review process.

2009 ◽  
Vol 87 (1) ◽  
pp. 283-306 ◽  
Author(s):  
Randall S. Gieni ◽  
Michael J. Hendzel
Keyword(s):  
Signal Transduction ◽  
Rna Polymerase ◽  
Serum Response Factor ◽  
Dynamic Equilibrium ◽  
Peer Review Process ◽  
Rna Polymerase I ◽  
Actin Dynamics ◽  
Nuclear Speckles ◽  
Polymerase I ◽  
Polymeric Actin

Actin exists as a dynamic equilibrium of monomers and polymers within the nucleus of living cells. It is utilized by the cell for many aspects of gene regulation, including mRNA processing, chromatin remodelling, and global gene expression. Polymeric actin is now specifically linked to transcription by RNA polymerase I, II, and III. An active process, requiring both actin polymers and myosin, appears to drive RNA polymerase I transcription, and is also implicated in long-range chromatin movement. This type of mechanism brings activated genes from separate chromosomal territories together, and then participates in their compartmentalization near nuclear speckles. Nuclear speckle formation requires polymeric actin, and factors promoting polymerization, such as profilin and PIP2, are concentrated there. A review of the literature shows that a functional population of G-actin cycles between the cytoplasm and the nucleoplasm. Its nuclear concentration is dependent on the cytoplasmic G-actin pool, as well as on the activity of import and export mechanisms and the availability of interactions that sequester it within the nucleus. The N-WASP-Arp2/3 actin polymer-nucleating mechanism functions in the nucleus, and its mediators, including NCK, PIP2, and Rac1, can be found in the nucleoplasm, where they likely influence the kinetics of polymer formation. The actin polymer species produced are tightly regulated, and may take on conformations not easily recognized by phalloidin. Many of the factors that cleave F-actin in the cytoplasm are present at high levels in the nucleoplasm, and are also likely to affect actin dynamics there. The absolute and relative G-actin content in the nucleoplasm and the cytoplasm of a cell contains information about the homeostatic state of that cell. We propose that the cycling of G-actin between the nucleus and cytoplasm represents a signal transduction mechanism that can function through both extremes of global cellular G-actin content. MAL signalling within the serum response factor pathway, when G-actin levels are low, represents a well-studied example of actin functioning in signal transduction. The translocation of NCK into the nucleus, along with G-actin, during dissolution of the cytoskeleton in response to DNA damage represents another instance of a unique signalling mechanism operating when G-actin levels are high.

Inactivation of rat liver RNA polymerases I and II and yeast RNA polymerase I by pyridoxal 5'-phosphate. Evidence for the participation of lysyl residues at the active site

Biochemistry ◽  
1975 ◽  
Vol 14 (22) ◽  
pp. 4907-4911 ◽  
Author(s):  
Joseph Martial ◽  
Josefina Zaldivar ◽  
Paulina Bull ◽  
Alejandro Venegas ◽  
Pablo Valenzuela
Keyword(s):  
Rna Polymerase ◽  
Rat Liver ◽  
Active Site ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Polymerase I

scholarly journals Histone Acetyltransferase and Protein Kinase Activities Copurify with a Putative Xenopus RNA Polymerase I Holoenzyme Self-Sufficient for Promoter-Dependent Transcription

1999 ◽  
Vol 19 (1) ◽  
pp. 796-806 ◽  
Author(s):  
Annie-Claude Albert ◽  
Michael Denton ◽  
Milko Kermekchiev ◽  
Craig S. Pikaard
Keyword(s):  
Rna Polymerase ◽  
Histone Acetyltransferase ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Large Mass ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Pol I ◽  
Coomassie Blue ◽  
Polymerase I

ABSTRACT Mounting evidence suggests that eukaryotic RNA polymerases preassociate with multiple transcription factors in the absence of DNA, forming RNA polymerase holoenzyme complexes. We have purified an apparent RNA polymerase I (Pol I) holoenzyme from Xenopus laevis cells by sequential chromatography on five columns: DEAE-Sepharose, Biorex 70, Sephacryl S300, Mono Q, and DNA-cellulose. Single fractions from every column programmed accurate promoter-dependent transcription. Upon gel filtration chromatography, the Pol I holoenzyme elutes at a position overlapping the peak of Blue Dextran, suggesting a molecular mass in the range of ∼2 MDa. Consistent with its large mass, Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gels reveal approximately 55 proteins in fractions purified to near homogeneity. Western blotting shows that TATA-binding protein precisely copurifies with holoenzyme activity, whereas the abundant Pol I transactivator upstream binding factor does not. Also copurifying with the holoenzyme are casein kinase II and a histone acetyltransferase activity with a substrate preference for histone H3. These results extend to Pol I the suggestion that signal transduction and chromatin-modifying activities are associated with eukaryotic RNA polymerases.

scholarly journals A Novel Assay for RNA Polymerase I Transcription Elongation Sheds Light on the Evolutionary Divergence of Eukaryotic RNA Polymerases

Biochemistry ◽  
2019 ◽  
Vol 58 (16) ◽  
pp. 2116-2124 ◽  
Author(s):  
Catherine E. Scull ◽  
Zachariah M. Ingram ◽  
Aaron L. Lucius ◽  
David A. Schneider
Keyword(s):  
Rna Polymerase ◽  
Transcription Elongation ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Evolutionary Divergence ◽  
Polymerase I

THE RNA POLYMERASES OF FUNGI. GLUTARIMIDES AND THE REGULATION OF RNA POLYMERASE I

Isozymes ◽  
1975 ◽  
pp. 69-87
Author(s):  
DAVID H. GRIFFIN ◽  
WILLIAM TIMBERLAKE ◽  
JOHN CHENEY ◽  
PAUL A HORGEN
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Polymerase I

Phosphorylation of RNA polymerases: specific association of protein kinase NIl with RNA polymerase I

1983 ◽  
Vol 302 (1108) ◽  
pp. 135-142 ◽  
Keyword(s):  
Protein Kinase ◽  
Rna Polymerase ◽  
Rna Synthesis ◽  
Rna Polymerase Iii ◽  
Rna Polymerases ◽  
Rna Polymerase I ◽  
Liver Protein ◽  
Protein Kinase N ◽  
Polymerase I

The activities of the three DNA-dependent RNA polymerases from a rapidly growing rat tumour, Morris hepatoma 3924 A, and from rat liver were examined. The activity of RNA polymerase I was higher in the tumour than in the liver. The enhanced capacity for RNA synthesis was a result of a higher concentration of polymerase I in the tumour as well as of an activation of this enzyme vivo. The possibility that the high specific activity of the hepatoma polymerase I resulted from phosphorylation was investigated. Two major cyclic-AMP-independent nuclear casein kinases (NI and N il) were identified; the activity of protein kinase N il in the tumour was ten times that in liver. Protein kinase N il was capable of activating and phosphorylating RNA polymerase I in vitro . This kinase could also stimulate RNA polymerase II activity, although to a lesser extent than RNA polymerase I. RNA polymerase III was not affected by protein kinase NIL Protein kinase N il was tightly associated with polymerase I and was found even in purified preparations of the polymerase. Antibodies against both RNA polymerase I and protein kinase N il were present in sera of patients with certain rheumatic autoimmune diseases. These results imply that RNA polymerase I and protein kinase NIl are in close association in vivo as well as in vitro and that polymerase phosphorylation may regulate the rate of ribosomal RNA synthesis in the cell.

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