The Footprint of Chromosomal Proteins HMG-14 and HMG-17 on Chromatin Subunits

Alfonso, Pedro J.; Crippa, Massimo P.; Hayes, Jeffrey J.; Bustin, Michael

doi:10.1006/jmbi.1994.1128

Cited by 65 publications

(81 citation statements)

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“…In vitro nucleosome binding assays indicate that each nucleosome has two high-affinity binding sites for either HMG-14 or HMG-17 (1,2,41,53). Consistent with these structural data, two or more molecules of HMG-14 or HMG-17 per nucleosome are required for maximal transcriptional activation on chromatin templates in both in vitro-reconstituted and in vivoassembled chromatin systems (17,19,46,61).…”

Section: Discussionmentioning

confidence: 59%

Alleviation of Histone H1-Mediated Transcriptional Repression and Chromatin Compaction by the Acidic Activation Region in Chromosomal Protein HMG-14

Ding

Bustin

Hansen

1997

Molecular and Cellular Biology

114

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Histone H1 promotes the generation of a condensed, transcriptionally inactive, higher-order chromatin structure. Consequently, histone H1 activity must be antagonized in order to convert chromatin to a transcriptionally competent, more extended structure. Using simian virus 40 minichromosomes as a model system, we now demonstrate that the nonhistone chromosomal protein HMG-14, which is known to preferentially associate with active chromatin, completely alleviates histone H1-mediated inhibition of transcription by RNA polymerase II. HMG-14 also partially disrupts histone H1-dependent compaction of chromatin. Both the transcriptional enhancement and chromatin-unfolding activities of HMG-14 are mediated through its acidic, C-terminal region. Strikingly, transcriptional and structural activities of HMG-14 are maintained upon replacement of the C-terminal fragment by acidic regions from either GAL4 or HMG-2. These data support the model that the acidic C terminus of HMG-14 is involved in unfolding higher-order chromatin structure to facilitate transcriptional activation of mammalian genes.In mammalian cells, genomic DNA is highly condensed, being organized in the nucleoprotein complex constituting chromatin (65,70). The packaging of genomic DNA into chromatin can inhibit gene expression in multiple ways: restricting the access of transcription factors to their promoter elements, blocking assembly and initiation by the general transcriptional machinery, and inhibiting elongation by the RNA polymerase. As a corollary, activation of transcription requires remodeling of the chromatin structure of the gene in order to relieve the repressive effects of chromatin on transcription (34,38,45,71,72).The building block of chromatin is the nucleosome, consisting of DNA wrapped twice around a histone octamer comprising the core histones H2A, H2B, H3, and H4. A linker histone, generally histone H1, interacts with DNA at several sites simultaneously (3, 51, 55, 58): (i) with DNA at or close to the entry and exit points of the nucleosome, (ii) with nucleosomal DNA over the dyad axis, after one wrap around the octamer, and (iii) with linker DNA between adjacent nucleosomal core particles. Within the interphase nucleus of higher eukaryotic cells, the linear array of nucleosomes is folded into a higherorder structure, called the 30-nm chromatin fiber (65, 70). Histone H1 plays a key role in the formation of such a higherorder chromatin structure (4, 37, 52, 59, 60).Biochemical and genetic studies have identified two distinct systems capable of remodeling the nucleosome structure for transcriptional activation. The multisubunit SWI/SNF complex, which is conserved from yeasts to humans (49, 69), can perturb the structure of a nucleosome in an ATP-dependent manner (15,29,35). This promotes the binding in vitro of either specific or general transcription factors, such as GAL4 and TBP, to their sites on nucleosomal DNA. A distinct nucleosome-remodeling factor (NURF), originally purified from Drosophila embryo extracts (63), is also capable ...

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Section: Discussionmentioning

confidence: 59%

Alleviation of Histone H1-Mediated Transcriptional Repression and Chromatin Compaction by the Acidic Activation Region in Chromosomal Protein HMG-14

Ding

Bustin

Hansen

1997

Molecular and Cellular Biology

114

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“…The NBD of HMGNs interferes mainly with the second step of H1 binding to chromatin, which involves the globular domain of H1 (12,38). Indeed, HMGN1 and HMGN2, which lack the long C terminus characteristic of HMGN5, interact with the dyad axis of the nucleosomal core particle (1). In summary, we concluded that HMGN5 competes with linker histone H1 by two different modes.…”

Section: Hmgn5 Is a Rapidly Evolving Proteinmentioning

confidence: 75%

Distinct Properties of Human HMGN5 Reveal a Rapidly Evolving but Functionally Conserved Nucleosome Binding Protein

Malicet

Rochman

Postnikov

et al. 2011

Molecular and Cellular Biology

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The HMGN family is a family of nucleosome-binding architectural proteins that affect the structure and function of chromatin in vertebrates. We report that the HMGN5 variant, encoded by a gene located on chromosome X, is a rapidly evolving protein with an acidic C-terminal domain that differs among vertebrate species. We found that the intranuclear organization and nucleosome interactions of human HMGN5 are distinct from those of mouse HMGN5 and that the C-terminal region of the protein is the main determinant of the chromatin interaction properties. Despite their apparent differences, both mouse and human HMGN5 proteins interact with histone H1, reduce its chromatin residence time, and can induce large-scale chromatin decompaction in living cells. Analysis of HMGN5 mutants suggests that distinct domains in HMGN5 affect specific steps in the interaction of H1 with chromatin. Elevated levels of either human or mouse HMGN5 affect the transcription of numerous genes, most in a variant-specific manner. Our study identifies HMGN5 as a rapidly evolving vertebrate nuclear protein with species-specific properties. HMGN5 has a highly disordered structure, binds dynamically to nucleosome core particles, modulates the binding of H1 to chromatin, reduces the compaction of the chromatin fiber, and affects transcription.

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“…2D). In this assay, the specific binding of either HMG14 or HMG17 to core particles results in a reduction in the mobility of core particles during native gel electrophoresis (Albright et al 1980;Mardian et al 1980;Sandeen et al 1980;Crippa et al 1992Crippa et al , 1993Alfonso et al 1994). Chromatin was assembled in the presence or absence of HMG17, purified by sucrose gradient sedimentation, digested extensively (to core particles) with micrococcal nuclease, and then subjected to electrophoresis on a nondenaturing polyacrylamide gel.…”

Section: Hmgi 7 Is Efficiently Incorporated Into Chromatin During Assmentioning

confidence: 99%

“…HMG14 and HMG17 are small (---10 kD), highly charged proteins that interact with high affinity to two distinct sites in nucleosomal cores (Albright et al 1980;Mardian et al 1980;Sandeen et al 1980;Shick et al 1985;Cook et al 1986;Crippa et al 1992Crippa et al , 1993Alfonso et al 1994). Moreover, HMG14/17 proteins bind with higher affinity to core particles than to naked DNA (Sandeen et al 1980).…”

mentioning

confidence: 99%

HMG17 is a chromatin-specific transcriptional coactivator that increases the efficiency of transcription initiation.

Paranjape¹,

Krumm²,

Kadonaga³

1995

Genes Dev.

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We have examined the effect of HMG17 on transcription by RNA polymerase II by the assembly and analysis of HMG17-containing chromatin templates consisting of regularly spaced nucleosomal arrays. Structural analysis of the chromatin indicated that HMG17 is incorporated into chromatin in a physiological manner with the full complement of core histones. The transcriptional studies revealed that HMG17 stimulates transcription in conjunction with the sequence-specific activator GAL4-VP16. This effect was observed with chromatin, but not with non-nucleosomal templates, and required the presence of HMG17 during chromatin assembly. The incorporation of HMG17 into chromatin resulted in a 7-to 40-fold stimulation of GAL4-VP16-activated transcription to levels that were comparable to those observed with histone-free DNA templates. In contrast, transcription from HMG17-containing chromatin was not detectable in the absence of GAL4--VP16 or with a GAL4 derivative [GAL4(1-147)] lacking the VP16 activation domain. Finally, the incorporation of HMG17 into chromatin was found to increase the efficiency of transcription initiation, but not the extent of transcriptional elongation. Thus, HMG17 is a chromatin-specific transcriptional coactivator that increases the efficiency of initiation of transcription by RNA polymerase II.

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The Footprint of Chromosomal Proteins HMG-14 and HMG-17 on Chromatin Subunits

Cited by 65 publications

References 0 publications

Alleviation of Histone H1-Mediated Transcriptional Repression and Chromatin Compaction by the Acidic Activation Region in Chromosomal Protein HMG-14

Alleviation of Histone H1-Mediated Transcriptional Repression and Chromatin Compaction by the Acidic Activation Region in Chromosomal Protein HMG-14

Distinct Properties of Human HMGN5 Reveal a Rapidly Evolving but Functionally Conserved Nucleosome Binding Protein

HMG17 is a chromatin-specific transcriptional coactivator that increases the efficiency of transcription initiation.

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