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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2006.04.029 Byline: Rushad Pavri (1), Bing Zhu (1), Guohong Li (1), Patrick Trojer (1), Subhrangsu Mandal (1), Ali Shilatifard (2), Danny Reinberg (1) Abstract: Over the past years, a large number of histone posttranslational modifications have been described, some of which function to attain a repressed chromatin structure, while others facilitate activation by allowing access of regulators to DNA. Histone H2B monoubiquitination is a mark associated with transcriptional activity. Using a highly reconstituted chromatin-transcription system incorporating the inducible RAR[beta]2 promoter, we find that the establishment of H2B monoubiquitination by RNF20/40 and UbcH6 is dependent on the transcription elongation regulator complex PAF, the histone chaperone FACT, and transcription. H2B monoubiquitination facilitates FACT function, thereby stimulating transcript elongation and the generation of longer transcripts. These in vitro analyses and corroborating in vivo experiments demonstrate that elongation by RNA polymerase II through the nucleosomal barrier is minimally dependent upon (1) FACT and (2) the recruitment of PAF and the H2B monoubiquitination machinery. Author Affiliation: (1) Howard Hughes Medical Institute, Department of Biochemistry, Division of Nucleic Acids Enzymology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 683 Hoes Lane, Piscataway, NJ 08854, USA (2) Department of Biochemistry, Saint Louis University School of Medicine, 1402 South Grand Boulevard, Saint Louis, MI 63104, USA Article History: Received 9 February 2006; Revised 23 March 2006; Accepted 20 April 2006 Article Note: (miscellaneous) Published: May 18, 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2006.04.003 Byline: Patrick Trojer (1), Danny Reinberg (1) Abstract: Methylation marks on the lysine residues of histone proteins are thought to contribute to epigenetic phenomena in part because of their apparent irreversibility. Will this view change with the recent discovery of histone lysine demethylases that reversibly remove methyl marks? Author Affiliation: (1) Howard Hughes Medical Institute, Department of Biochemistry, Division of Nucleic Acids Enzymology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA

The existence of the cytosolic Ezh2-containing methyltransferase complex and tie the function of this complex to regulation of actin polymerization in various cell types is reported. The function of Ezh2 points to a broader usage of lysine methylation in regulation of nuclear and extra- nuclear signaling processes.

The authors review the publications on human genome. The topics of interest include a unified theory of gene expression, the role of chromatin structure in gene expression and gene expression regulation.

Research has been conducted on the inherited mutations of the TFIIH helicase subunits xeroderma pigmentosum. Results indicate that the xeroderma pigmentosum mutations block transcription activation by the FUSE Binding Protein (FBP) and repression by the FBP Interacting Repressor.

Transcriptional repression, which is essential to the precise control of gene expression, is discussed in this review article which focuses on repressors that affect formation of the initiation complex. Several functionally distinct general repressors of transcription are analyzed. Topics include the relationship between nucleosomes and general repressors, the Dr1/Drap1 complex, Mot1, the Srb10/Srb11 complex, the Not complexes, and multifunctional repressors.

Structurally distinct, multisubunit complexes mediating activation and repression of transcription, were found to catalyze histone acetylation and deacetylation. ATP-dependent nucleosome remodeling was believed to be involved only in transcription activation. A protein complex has been isolated, containing both histone deacetylation and ATP-dependent nucleosome remodeling activities. It contains the histone deacetylases HDAC1/2, and the dermatomyositis-specific autoantigen Mi2Beta.

Research was conducted to investigate transcriptional activation requirements by RNA polymerase II (RNAP II) using chromatic templates. A factor that facilitated chromatic transcription was purified while an S-190 assembly extract was characterized from Drosophila embryos. Results indicated that RNAP II elongation factors can be divided into two classes and that the productive transcription on chromatin templates were correlated with the action of factors from RNAP II and its general transcription factors.

A new Rb-associated polypeptide, mSin3-associated polypeptide (SAP18) was identified by using the Western blot analysis and was isolated from HDAC1 and HDAC2 by using microsequencing. In vitro interaction between SAP18 and mSin3 was established using radiolabeled transcription-translation system, while in vivo interaction was demonstrated by using immunoprecipitation. Furthermore, it was found that SAP18 can influence the synthesis of a repressive complex thus, promoting mSin3-HDAC1-mediated transcriptional repression.

The three-dimensional structure determination studies of the human TFIIB core domain (TFIIBc) by single, double and triple nuclear magnetic resonance spectroscopy, reveal the presence of two repeats of alpha helical folds that appear to give a two-fold symmetry to the molecule. There is a basic surface at the center which is essential for its function. The structure of TFBIIc resembles that of cyclin A, suggesting a link between transcription and cell cycle molecular mechanisms.

Studies of DNA repair in various systems have led to two models of transcription-repair coupling in humans. The XPB and XPD move, according to the first model, with the elongating polymerase and are delivered to the site of damage by RNAPII. A new model suggests that XPB and XPD act independent of each other. Mutations of coupling factor, RNAP and subunits may lead to the uncoupling of transcription from repair.