Compartmentalization of regulatory proteins in the cell nucleus

Hendzel, Michael J.; Kruhlak, Michael J.; MacLean, Natalie A.B; Boisvert, François-Michel; Lever, Melody A.; Bazett-Jones, David P.

doi:10.1016/s0960-0760(00)00153-9

Cited by 41 publications

(46 citation statements)

References 117 publications

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“…Although unexpected, this finding reflects a possible mode of regulating Elongator function by cellular localization and transport to the nucleus. In support of our findings are results that uncovered interaction between the Elp2 subunit of Elongator and Stat3 and other polypeptides involved in the IFN signal transduction pathway (31). Importantly, Elp2 was found localized to the cytoplasm, but upon IL6 treatment, Elp2 translocated to the nucleus (30).…”

Section: Discussionsupporting

confidence: 85%

Human Elongator facilitates RNA polymerase II transcription through chromatin

Kim

Lane

Reinberg

2002

Proc. Natl. Acad. Sci. U.S.A.

150

146

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A human Elongator complex was purified from HeLa cells and found to be composed of three polypeptides. Human Elongator contains histone acetyltransferase activity with specificity to histone H3 and, to a much lesser extent, to histone H4. Although many reports have suggested a role for the yeast Elongator in transcription elongation through chromatin templates, no direct evidence supporting this function exists. In the present study, we demonstrate that the human Elongator facilitates transcription by RNA polymerase II in a chromatin-and acetyl-CoA-dependent manner. The complex was found to directly interact with RNA polymerase II but failed to interact with other factors that facilitated RNA polymerase II to traverse through nucleosomes. From our results, we postulate that different mechanisms operate to ensure efficient transcription by RNA polymerase II on chromatin templates.T he formation of a transcription initiation complex at a particular promoter is a complicated and highly regulated process. However, the establishment of a transcription initiation complex seems much simpler than the process of transcription elongation with respect to the chromatin impediment, where the elongating polymerase has to traverse a nucleosome approximately every 200 base pairs (1).The complexity of elongation by RNA polymerase II (RNA-PII) was recognized early by Price, who postulated the existence of positive and negative elongation-specific regulatory factors (2). This hypothesis gained validity when factors such as P-TEFb (3), and the positive and negative regulatory elongation factors DSIF (4) and NELF (5), respectively, were isolated. However, whether these factors are chromatin specific or general elongation factors affecting the efficiency of elongation, like TFIIS (6), remains an open question. Thus far, only one functional biochemical assay has been devised to score for chromatin-specific elongation factors (7). This biochemical assay resulted in the identification of FACT, an abundant factor conserved through evolution and composed of two subunits, SSRP1 and Spt16, which in a reconstituted transcription system allows RNAPII to traverse nucleosomes (8). The finding that Spt16 interacts with SAS3, the catalytic subunit of the histone acetyltransferase (HAT) NuA3 complex (9), provides a possible mechanism explaining the extent of acetylation observed at transcriptionally active regions, as it is unlikely that promoter activity can account for such extended acetylation. An alternative possibility that could account for the extended acetylation observed within transcriptionally active regions is that the elongating RNAPII is associated with a HAT complex (1). Evidence supporting this possibility was provided by the identification of the Elongator in yeast (10).Yeast Elongator was isolated as a complex that associates with the chromatin fraction and interacts with the elongating phosphorylated form of RNAPII (10). Elongator was initially found to be composed of three polypeptides (10-12). Its larger subunit is encoded by ...

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Section: Discussionsupporting

confidence: 85%

Human Elongator facilitates RNA polymerase II transcription through chromatin

Kim

Lane

Reinberg

2002

Proc. Natl. Acad. Sci. U.S.A.

150

146

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“…2 In contrast, in 3T3-F442A cells, C/EBP␦ does not localize in areas of heterochromatin even when the cells undergo adipocyte differentiation. 2 This observation reinforces the existence of differences in spatial organization in the nucleus between different cell lines which may account for differential regulation of localization of nuclear factors and differential transcriptional regulation.…”

Section: Discussionmentioning

confidence: 94%

“…It is possible that cell type specific nuclear architecture may also contribute to the differential distribution of a transcription factor, since in 3T3L1 cells undergoing adipocyte differentiation C/EBP␦, as well as C/EBP␤ and C/EBP␣, localize in areas of pericentric heterochromatin (22). 2 In contrast, in 3T3-F442A cells, C/EBP␦ does not localize in areas of heterochromatin even when the cells undergo adipocyte differentiation. 2 This observation reinforces the existence of differences in spatial organization in the nucleus between different cell lines which may account for differential regulation of localization of nuclear factors and differential transcriptional regulation.…”

Section: Discussionmentioning

confidence: 99%

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Subnuclear Localization of C/EBPβ Is Regulated by Growth Hormone and Dependent on MAPK

Pilipuk

Galigniana

Schwartz

2003

Journal of Biological Chemistry

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Localization of transcription regulatory proteins in the nucleus is dynamically regulated, and may alter nucleoplasmic concentrations and/or assembly of multimolecular transcription regulatory complexes, which ultimately regulate gene expression. Since growth hormone (GH) regulates multiple transcription factors including C/EBP␤, the effect of GH on the subcellular localization of C/EBP␤ was examined in 3T3-F442A preadipocytes. Indirect immunofluorescence shows that C/EBP␤ is diffusely distributed in nuclei of quiescent cells. . Indirect immunofluorescence using antibodies specific for C/EBP␤ phosphorylated on the conserved MAPK site shows that GH also rapidly induces a punctate pattern of staining for the phosphorylated C/EBP␤. In addition, phosphorylated C/EBP␤ colocalizes to pericentromeric heterochromatin. The satellite DNA present in heterochromatin contains multiple C/EBP binding sites. DNA binding analysis shows that C/EBP␤, C/EBP␦, and C/EBP␣ (p42 and p30 forms) can bind to satellite DNA as homo-or heterocomplexes in vitro. Importantly, GH rapidly and transiently increases binding of endogenous C/EBP␤ from 3T3-F442A cells to satellite DNA. Further, the GH-promoted nuclear relocalization of C/EBP␤ to pericentromeric heterochromatin was prevented by the MEK inhibitor U0126. This observation suggests that GH-dependent MAPK activation plays a role in the regulation of nuclear relocalization of C/EBP␤. Nuclear redistribution introduces a new level of transcriptional regulation in GH action, since GHmediated phosphorylation and nuclear redistribution of C/EBP␤ may be coordinated to achieve spatial-temporal control of gene expression.Chromatin is organized into higher order fibers in interphase chromosomes, which localize into discrete territories, providing an excellent scenario for establishing spatio-temporal regulation of gene transcription (1, 2). Transcriptional regulatory proteins are generally restricted to several hundred discrete foci throughout the nucleoplasm (3, 4). Interestingly, foci rich in some transcription factors such as E2F-1 or Oct1 show only minor overlap with sites of transcription or RNA polymerase II (3, 4), whereas steroid hormone receptors and RNA polymerase II show significant colocalization (5, 6). Thus, the function of the transcription factor-rich foci in the nucleus that do not contain RNA polymerase II or nascent RNA is unclear. A simple explanation is that foci represent nonchromatin structures that function in the regulation of nucleoplasmic concentrations of gene regulatory factors and/or the assembly of multimolecular transcription factor complexes. This subnuclear

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“…Both protein acetylation and protein phosphorylation alter residency times [34,35] Nucleosomal histones t 1=2 of 2 or more hours t 1=2 P 2 h H2B exchanged more rapidly than H3/H4; part of the exchanging H2B population was dependent on RNA polymerase II transcription [36] [39] Glucocorticoid receptor ''Rapid'' seconds time scale Stimulated receptor has short residency time on its target DNA in living cell system [40] SRC-1 $10 s in presence of estradiol Mobility reduced in ER cotransfected cells in the presence of estradiol but not other treatments, e.g., inhibitor, that reduce ER mobility [38] an increasingly important role in advancing our understanding of the behavior and function of proteins within the cytoplasm and cellular compartments such as the nucleus.…”

Section: Introductionmentioning

confidence: 99%