Posttranslational Regulation of Human DNA Polymerase ι

Human DNA polymerases (pols) η and ι are Y-family DNA polymerase paralogs that facilitate translesion synthesis past damaged DNA. Both polη and polι can be monoubiquitinated in vivo. Polη has been shown to be ubiquitinated at one primary site. When this site is unavailable, three nearby lysines may become ubiquitinated. In contrast, mass spectrometry analysis of monoubiquitinated polι revealed that it is ubiquitinated at over 27 unique sites. Many of these sites are localized in different functional domains of the protein, including the catalytic polymerase domain, the proliferating cell nuclear antigen-interacting region, the Rev1-interacting region, and its ubiquitin binding motifs UBM1 and UBM2. Polι monoubiquitination remains unchanged after cells are exposed to DNA-damaging agents such as UV light (generating UV photoproducts), ethyl methanesulfonate (generating alkylation damage), mitomycin C (generating interstrand cross-links), or potassium bromate (generating direct oxidative DNA damage). However, when exposed to naphthoquinones, such as menadione and plumbagin, which cause indirect oxidative damage through mitochondrial dysfunction, polι becomes transiently polyubiquitinated via Lys¹¹- and Lys⁴⁸-linked chains of ubiquitin and subsequently targeted for degradation. Polyubiquitination does not occur as a direct result of the perturbation of the redox cycle as no polyubiquitination was observed after treatment with rotenone or antimycin A, which both inhibit mitochondrial electron transport. Interestingly, polyubiquitination was observed after the inhibition of the lysine acetyltransferase KATB3/p300. We hypothesize that the formation of polyubiquitination chains attached to polι occurs via the interplay between lysine acetylation and ubiquitination of ubiquitin itself at Lys¹¹ and Lys⁴⁸ rather than oxidative damage per se.     

Neuronal non-CG methylation is an essential target for MeCP2 function

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Fibrous Aggregates of Short Peptides Containing Two Distinct Aromatic Amino Acid Residues

The aim of the study was the assessment of the ability of short peptides to form aggregates under physiological conditions. The dipeptides studied were derived from different aromatic amino acids (heteroaromatic peptides). Tripeptides were obtained from two distinct aromatic amino acids and cysteine or methionine residue in the C‐terminal, N‐terminal, or central position. The ability of the peptides to form fibrous aggregates under physiological conditions was evaluated using three independent methods: the Congo Red assay, the Thioflavin T assay, and microscopic examinations using normal and polarized light. Materials potentially useful for regenerative medicine were selected based on their cytotoxicity to the endothelial cell line EA.hy 926 and physicochemical properties of films formed by peptides. The required parameters of biocompatibility were fulfilled by H?PheCysTrp?OH, H?PheCysTyr?OH, H?PheTyrMet?OH, and H?TrpTyr?OH.     

SOD-Like Activity of Copper(II) Containing Metallopeptides Branched By 2,3-Diaminopropionic Acid: What the N-Termini Elevate,the C-Terminus Ruins

International Journal of Peptide Research and Therapeutics - Relations between structural modifiactions and SOD-like activity of four branched CuII-metallopeptides based on l-2,3-diaminopropionic...     

Antimicrobial and antioxidative potential of free and immobilised cellobiose dehydrogenase isolated from wood degrading fungi

Cellobiose dehydrogenase (CDH, EC 1.1.99.18) is a glycoprotein having many biotechnological applications. In the present study, CDHs isolated from Phlebia lindtneri (PlCDH), Phanerochaete chrysosporium (PchCDH), Cerrena unicolor (CuCDH), and Pycnoporus sanguineus (PsCDH) were studied the first time for their ability to generate antioxidant and antimicrobial agents. The aim of the research was to evaluate the antioxidant and antimicrobial activity of systems composed of four CDHs and lactose or cellobiose as a reaction substrate. The free radical scavenging effect of free and immobilised enzymes was evaluated using the DPPH method. The lowest values of EC₅₀ (10.04 ± 0.75 $\text{μg}$/ml) was noted for PlCDH/lactose and for PlCDH/cellobiose (12.06 ± 1.35 $\text{μg}$/ml). The EC₅₀value reached 12.6 ± 1.51 $\text{μg}$/ml in the case of PsCDH/lactose and 15.96 ± 1.35 for PsCDH. The CDH preparations were also effectively immobilised in alginate (the immobilisation efficiency expressed as a protein yield ranged from 61.6 to 100 %). The operational stability expressed as a scavenging effect showed the possibility of using the alginate beads 4 times. Both the free and immobilised CDHs as well as the CDH/substrate were tested against Gram-negative Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Gram-positive Staphylococcus aureus ATCC 25923 bacteria. All samples, except PlCDH, were potentially effective in suppression of bacterial growth. The highest percentage of inhibition (100 %) was obtained for S. aureus bacteria using PsCDH and PchCDH with lactose as a substrate, whereas a slightly lesser effect was observed for E. coli and P. aeruginosa bacterial cells, i.e. 64.1 % and 86.5 % (PsCDH) and 94.1 % and 41.4 % (PchCDH), respectively. Furthermore, the concentrations of the reaction products (aldonic acids and hydrogen peroxide) were quantified and the surface morphology of the alginate beads was analysed using SEM visualisation.