Effects of Histone H2B Ubiquitylations and H3K79me on Transcription Elongation.

Post-translational modifications of histone proteins often mediate gene regulation by altering the global and local stability of the nucleosome, the basic gene-packing unit of eukaryotes. We employed semisynthetic approaches to introduce histone H2B ubiquitylations at K34 (H2BK34ub) and K120 (H2BK120ub) and H3K79 trimethylation (H3K79me3). With these modified histones, we investigated their effects on the kinetics of transcription elongation by RNA polymerase II (Pol II) using single-molecule FRET.

The Effects of Histone H2B Ubiquitylations on the Nucleosome Structure and Internucleosomal Interactions.

Eukaryotic gene compaction takes place at multiple levels to package DNA to chromatin and chromosomes. Two of the most fundamental levels of DNA packaging are at the nucleosome and dinucleosome stacks. The nucleosome is the basic gene-packing unit and is composed of DNA wrapped around a histone core.

Histone Modifications, Internucleosome Dynamics, and DNA Stresses: How They Cooperate to "Functionalize" Nucleosomes.

Tight packaging of DNA in chromatin severely constrains DNA accessibility and dynamics. In contrast, nucleosomes in active chromatin state are highly flexible, can exchange their histones, and are virtually "transparent" to RNA polymerases, which transcribe through gene bodies at rates comparable to that of naked DNA. Defining mechanisms that revert nucleosome repression, in addition to their value for basic science, is of key importance for the diagnosis and treatment of genetic diseases.

"Direct" and "Indirect" Effects of Histone Modifications: Modulation of Sterical Bulk as a Novel Source of Functionality.

The chromatin-regulatory principles of histone post-translational modifications (PTMs) are discussed with a focus on the potential alterations in chromatin functional state due to steric and mechanical constraints imposed by bulky histone modifications such as ubiquitin and SUMO. In the classical view, PTMs operate as recruitment platforms for histone "readers," and as determinants of chromatin array compaction. Alterations of histone charges by "small" chemical modifications (e.

Ubiquitylation: How Nucleosomes Use Histones to Evict Histones.

Steric hindrances by bulky histone modifications (such as ubiquitylation) could destabilize and remodel canonical nucleosome structure. This highlights a novel mechanism by which bulky modifications directly regulate chromatin, distinct from the more generally accepted roles of histone modifications in the recruitment of downstream effectors and histone charge shielding.

Analysis of histone ubiquitylation by MSL1/MSL2 proteins in vitro.

Histone posttranslational modifications (PTM) control gene activity by targeting chromatin-regulatory proteins. By altering histone charges PTMs could also modulate inter- and intra-nucleosomal interactions, and thus affect chromatin high-order compaction and nucleosome stochastic folding, respectively. However, recently it has been shown that histone H2BK34- ubiquitylation (which is deposited in vivo by MOF-MSL) can destabilize one of the nucleosomal H2A-H2B dimers in symmetrically and (albeit to a lesser extend) asymmetrically modified nucleosomes, and thus promote formation of a hexasome particle.

Proteasome functioning in breast cancer: connection with clinical-pathological factors.

Breast cancer is one of four oncology diseases that are most widespread in the world. Moreover, breast cancer is one of leading causes of cancer-related deaths in female population within economically developed regions of the world. So far, detection of new mechanisms of breast cancer development is very important for discovery of novel areas in which therapy approaches may be elaborated.

Ontogenesis of rat immune system: Proteasome expression in different cell populations of the developing thymus.

Immune proteasomes in thymus are involved in processing of self-antigens, which are presented by MHC class I molecules for rejection of autoreactive thymocytes in adults and probably in perinatal rats. The distribution of immune proteasome subunits LMP7 and LMP2 in thymic cells have been investigated during rat perinatal ontogenesis. Double immunofluorescent labeling revealed LMP7 and LMP2 in thymic epithelial and dendritic cells, as well as in CD68 positive cells - macrophages, monocytes - at all developmental stages.

New approach to study of T cellular immunity development: parallel investigation of lymphoid organ formation and changes in immune proteasome amount in rat early ontogenesis.

The expression pattern and distribution of proteasome immune subunits LMP7 and LMP2 in the developing rat spleen and liver as well as the periarterial lymphoid sheath formation were investigated. LMP7 and LMP2 were detected by immunoblotting in the spleen on the 21st embryonic day and during the first postnatal days in equal amounts. Their levels increased by the 8th and 18th postnatal days.