Purification and characterization of a high-mobility-group-like DNA-binding protein that stimulates rRNA synthesis in vitro.

Yang-Yen, Hsin-Fang; Rothblum, L I

doi:10.1128/mcb.8.8.3406

Cited by 51 publications

(26 citation statements)

References 49 publications

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“…It has been implicated in metaphase chromatin condensation (33), heterochromatin nucleosome phasing (53), nuclear matrix-DNA interactions (11), 3'-end processing of genes (42,49), and the formation of active initiation complexes (61,65). HMG-I is preferentially expressed at high levels in undifferentiated, neoplastically transformed, and rapidly proliferating cells (5,14,17,18,22,23,33,60); it is predicted to undergo a wide variety of posttranslational modifications (14), some of which are expected to alter its affinity for DNA.…”

Section: Discussionmentioning

confidence: 99%

A poly(dA-dT) upstream activating sequence binds high-mobility group I protein and contributes to lymphotoxin (tumor necrosis factor-beta) gene regulation.

Fashena¹,

Reeves²,

Ruddle³

1992

Mol. Cell. Biol.

106

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Lymphotoxin (LT; also known as tumor necrosis factor-,) is a pleiotropic cytokine whose expression is tightly regulated in most cells and is repressed prior to activation signals. In some early B cells and Abelson murine leukemia virus-transformed pre-B-cell lines, LT mRNA is constitutively expressed. To examine the molecular regulation of the LT gene in a constitutively expressing cell line, we studied the Abelson murine leukemia virus-transformed lines PD and PD31. As demonstrated by primer extension analysis, constitutively expressed pre-B-cell-derived and inducibly expressed T-cell-derived LT mRNA were initiated at the same cap sites and predominant cap site utilization was conserved. Furthermore, we delineated an upstream activating sequence that was an important functional component of lymphotoxin transcriptional activation in PD and PD31 cells. The upstream activating sequence was localized to an essentially homopolymeric A+T-rich region (LT-612/-580), which was bound specifically by recombinant human high-mobility group I protein (HMG-I) and a PD/PD31 nuclear extract HMG-I (HMG-I-like) protein. The nuclear extract-derived HMG-I-like protein was recognized by anti-HMG-I antibody and bound to LT DNA to effect an electrophoretic mobility shift identical to that of bound recombinant human HMG-I. These findings implicate HMG-I in the regulation of constitutive lymphotoxin gene expression in PD and PD31 cells. HMG-I and HMG-I-like proteins could facilitate the formation of active initiation complexes by altering chromatin structure and/or by creating recognition sites for other activator DNA-binding proteins, some of which may be unique to or uniquely modified in these constitutive LT mRNA producers.Lymphotoxin (LT; also known as tumor necrosis factor-P), the product of a gene encoded within the major histocompatibility complex (34, 35) is a pleiotropic cytokine whose expression is tightly regulated in most cells. LT transcription is induced in T cells by activation with specific antigen in the context of syngeneic major histocompatibility complex, mitogens, or phorbol esters (reviewed in reference 39). Lipopolysaccharide, phorbol esters, Staphylococcus aureus Cowan 1, B-cell growth factor, and anti-p. antibodies, alone and in combination, can also induce its production by some B cells (37; reviewed in reference 59). LT is regulated differently in some early B-cell lines and Abelson murine leukemia virus (A-MuLV)-transformed murine pre-B cell lines in that these cells constitutively produce high levels of LT mRNA (15,29). The mechanism(s) of constitutive LT mRNA accumulation in the A-MuLV-transformed pre-B-cell lines PD and PD31 may operate on several levels. One possible explanation for LT mRNA accumulation is that the promoter, which is repressed in normal T and B cells prior to cellular activation (reviewed in references 16 and 39), functions constitutively in these pre-B-cell lines. Constitutive LT promoter activity could be associated with the function of upstream positive regulatory elements that transcr...

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Section: Discussionmentioning

confidence: 99%

A poly(dA-dT) upstream activating sequence binds high-mobility group I protein and contributes to lymphotoxin (tumor necrosis factor-beta) gene regulation.

Fashena¹,

Reeves²,

Ruddle³

1992

Mol. Cell. Biol.

106

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“…This has led to the suggestion that they could be chromosomal structural proteins [ 131. However, recently it has been shown that HMGI proteins bind specifically to the AT-rich octamer sequence associated with a number of promoters and also to AT-rich regulatory elements of the ribosomal genes [15,16]. The finding that they can activate transcription in vitro [16] and that they have an acidic Cterminal region which is phosphorylated suggests that they …”

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confidence: 99%

Comparison of multiple forms of the high mobility group I proteins in rodent and human cells

Giancotti

Bandiera

Buratti

et al. 1991

European Journal of Biochemistry

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The class I of the high mobility group (HMG) proteins is formed by phosphoproteins which are associated with AT-rich DNA sequences in the nucleus. Three HMGI proteins have previously been described in proliferating rodent cells (HMG Y, HMG I and HMGI-C). All three proteins exhibit microheterogeneity. The microheterogeneity of mouse HMG Y has been investigated in detail and shown to be due to phosphorylation of the protein which is sensitive to alkaline-phosphatase treatment. HMG I is similarly modified. Human cells have up to now only been found to contain HMG Y and HMG I. A search for the third protein, HMGI-C, in human cells was carried out and the protein was found in a hepatoma cell line, but not in normal or transformed T-cells. This HMGI-C protein was found to be modified by phosphorylation, part of which was found to be phosphatase insensitive. An unexpected additional finding in this study was that human cells contain two HMG17 proteins which differ in their N-terminal primary sequences.The HMG proteins are an abundant family of non-histone proteins found in the cell nucleus of vertebrate and invertebrate organisms [l, 21. In mammalian, avian and fish cells there are three classes of such proteins, all characterised by having a high content of basic and acidic amino acids.The HMGIIZ class ofproteins. These are highly structured proteins containing two so-called HMG boxes which are homologous to a number of transcription factors and other regulatory molecules and are involved in DNA-binding. There are multiple forms of these proteins in all cell types though the distribution of subfractions can differ between cells. The function of these proteins is not known, but there is a strong possibility that they are transcription factors, given their similar structure to ribosomal-gene-transcription factors UBF [3].The HMG14117 class. This class of random-coiled proteins is found at slightly higher levels (twofold) in chromatin fractions containing transcriptionally active genomes, but their function is still not known [l, 21.The HMGI class of proteins. Two such proteins HMG I and HMG Y, were originally described in HeLa cells by Lund et al. [4] and were later shown to be present in rodent and simian cells [ 5 , 61. The cDNAs for these two proteins were

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“…Initiation at the ribosomal gene promoter can be stimulated by many different sequence elements operating via several distinct mechanisms. Stimulation can result not only from enhancers, but also from terminators (11,25,26,36), spacer promoters (10), and high-mobility-group-like protein binding sites (58). We would like to see the term enhancer reserved for those in vivo stimulatory elements which are analogous to the Xenopus and mouse enhancers and which match the criteria listed at the beginning of this discussion.…”

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confidence: 99%

Enhancers for RNA polymerase I in mouse ribosomal DNA.

Pikaard¹,

Pape²,

Henderson³

et al. 1990

Mol. Cell. Biol.

104

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The intergenic spacer of the mouse ribosomal genes contains repetitive 140-base-pair (bp) elements which we show are enhancers for RNA polymerase I transcription analogous to the 60/81-bp repetitive enhancers (enhancers containing a 60-bp and an 81-bp element) previously characterized from Xenopus laevis. In rodent cell transfection assays, the 140-bp repeats stimulated an adjacent mouse polymerase I promoter when located in cis and competed with it when located in trans. Remarkably, in frog oocyte injection assays, the 140-bp repeats enhanced a frog ribosomal gene promoter as strongly as did the homologous 60/81-bp repeats. Mouse 140-bp repeats also competed against frog promoters in trans. The 140-bp repeats bound UBF, a DNA-binding protein we have purified from mouse extracts that is the mouse homolog of polymerase I transcription factors previously isolated from frogs and humans. The DNA-binding properties of UBF are conserved from the mouse to the frog. The same regulatory elements (terminators, gene and spacer promoters, and enhancers) have now been identified in both a mammalian and an amphibian spacer, and they are found in the same relative order. Therefore, this arrangement of elements probably is consequences.widespread in nature and has important functionalThe genes coding for the large rRNAs of most eucaryotes are organized in a similar fashion. From yeast cells to humans, these genes are arranged in multiple tandem copies with precursor-coding regions separated from each other by intergenic spacers (reviewed in references 42 and 54). Recent work from a number of laboratories has suggested that, at least among the multicellular eucaryotes, there is also a broadly conserved arrangement of transcriptional regulatory elements in the spacer (reviewed in reference 49a). The ribosomal genes of the frog, Xenopus laevis, may be considered a paradigm for this type of organization since all of the known regulatory elements have been identified in this organism.A typical intergenic spacer from an X. laevis ribosomal gene is shown in the top line of Fig. 1, with the spacer from a mouse ribosomal gene shown below for comparison. In X. laevis, the intergenic spacer is bounded on the left by a site for 3'-end formation of the precursor (31) and on the right by the gene promoter that directs initiation of the precursor transcript. Between these points are located one or more spacer promoters (4, 41, 53) (the only other known promoters that are recognized by polymerase I), and downstream of the spacer promoters are repetitive 60-and 81-base-pair (bp) elements (60/81-bp elements) that act as enhancers for polymerase I transcription and are additive in effect (11,30,44,48). Between the enhancers and the gene promoter is a termination site (31, 40). The 60/81-bp enhancers bind a Xenopus transcription factor, xUBF, which also binds to the gene promoter (47) and is the frog homolog of human UBF (hUBF; 2) and rat UBF (rUBF; 48a), factors which also stimulate transcription from the gene promoters of these species. The frog...

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Purification and characterization of a high-mobility-group-like DNA-binding protein that stimulates rRNA synthesis in vitro.

Cited by 51 publications

References 49 publications

A poly(dA-dT) upstream activating sequence binds high-mobility group I protein and contributes to lymphotoxin (tumor necrosis factor-beta) gene regulation.

A poly(dA-dT) upstream activating sequence binds high-mobility group I protein and contributes to lymphotoxin (tumor necrosis factor-beta) gene regulation.

Comparison of multiple forms of the high mobility group I proteins in rodent and human cells

Enhancers for RNA polymerase I in mouse ribosomal DNA.

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