In higher eukaryotic cells, DNA is tandemly arranged into 10⁴ replicons that are replicated once per cell cycle during the S phase. To achieve this, DNA is organized into loops attached to the nuclear matrix. Each loop represents one individual replicon with the origin of replication localized within the loop and the ends of the replicon attached to the nuclear matrix at the bases of the loop. During late G₁ phase, the replication origins are associated with the nuclear matrix and dissociated after initiation of replication in S phase. Clusters of several replicons are operated together by replication factories, assembled at the nuclear matrix. During replication, DNA of each replicon is spooled through these factories, and after completion of DNA synthesis of any cluster of replicons, the respective replication factories are dismantled and assembled at the next cluster to be replicated. Upon completion of replication of any replicon cluster, the resulting entangled loops of the newly synthesized DNA are resolved by topoisomerases present in the nuclear matrix at the sites of attachment of the loops. Thus, the nuclear matrix plays a dual role in the process of DNA replication: on one hand, it represents structural support for the replication machinery and on the other, provides key protein factors for initiation, elongation, and termination of the replication of eukaryotic DNA. J. Cell. Biochem.

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DNA of replication foci attached to the nuclear matrix was isolated from Chinese hamster ovary cells and human HeLa cells synchronized at different stages of the G₁ and S phases of the cell cycle. The abundance of sequences from dihydrofolate reductase ori-β and the β-globin replicator was determined in matrix-attached DNA. The results show that matrix-attached DNA isolated from cells in late G₁ phase was enriched in origin sequences in comparison with matrix-attached DNA from early G₁ phase cells. The concentration of the early firing ori-β in DNA attached to the matrix decreased in early S phase, while the late firing β-globin origin remained attached until late S phase. We conclude that replication origins associate with the nuclear matrix in late G₁ phase and dissociate after initiation of DNA replication in S phase.

Algal metabolites have been extensively studied as potential anticancer therapeutics. Among them, polysaccharides have attracted much attention because of their beneficial biological effects and safety. In the present research, the chemical characteristics, antitumor, and proapoptotic activities of extracellular polysaccharides (EPS) isolated from a new Bulgarian strain of the green microalga Coelastrella sp. BGV were investigated. A fast and convenient method of precipitation with cold ethanol was used to isolate EPS from the culture medium. The chemical characteristics of the isolated EPS were examined by colorimetric and spectrophotometric analyses, HPSEC-RID and HPLC-UV chromatography, and FT-IR spectroscopy. The results showed that the isolated EPS sample consists of three carbohydrate fractions with different molecular weights (11.5 × 10⁴ Da, 30.7 × 10⁴ Da, and 72.4 × 10⁴ Da, respectively) and contains 7.14 (w/w%) protein. HPLC-UV analysis revealed the presence of galactose and fucose. The total uronic acid content in the sample was 4.5 (w/w%). The IR-FT spectrum of EPS revealed the presence of various functional groups typical of a polysaccharide (or proteoglycan) composed primarily of neutral sugars. The anticancer potential of the obtained EPS was assessed using cell lines with cancerous and non-cancerous origins as in vitro experimental models. The results of the performed MTT assay showed that EPS reduced the viability of the cervical and mammary carcinoma cell lines HeLa and MCF-7, while the control non-cancer cell lines BALB/3T3 and HaCaT were less affected. The HeLa cell line showed the highest sensitivity to the effects of EPS and was therefore used for further studies of its anticancer potential. The ability of EPS to inhibit cancer cell migration was demonstrated by wound-healing (scratch) assay. The cell cycle FACS analysis indicated that the EPS treatment induced significant increases in the sub G1 cell population and decreases of the percentages of cells in the G1, S, and G2-M phases, compared to the control. The fluorescent microscopy studies performed using three different staining methods in combination with Annexin V-FITC flow cytometric analysis clearly demonstrate the ability of EPS to induce cancer cell death via the apoptosis pathway. Moreover, an altered pattern and intensity of the immunocytochemical staining for the apoptosis- and proliferation-related proteins p53, bcl2, and Ki67 was detected in EPS-treated HeLa cancer cells as compared to the untreated controls. The obtained results characterize the new local strain of green microalgae Coelastrella sp. BGV as a producer of EPS with selective antitumor activity and provide an opportunity for further studies of its pharmacological and biotechnological potential.

Salvia aethiopis L. (Mediterranean sage) is a medicinal plant known for its rich phenolic content and different therapeutic properties. This study evaluated the phytochemical composition, antioxidant capacity and anticancer potential of water extracts from in vitro cultivated S. aethiopis. The extract exhibited a high total polyphenol (110.03 ± 0.7 mg GAE/g) and flavonoid (7.88 ± 0.25 mg QE/g) content, along with a strong oxygen radical absorbance capacity (an ORAC value of 3677.9 ± 24.8 µmol TE/g). LC-HRMS analysis identified 21 bioactive compounds, including salvianic acid C, rosmarinic acid, salvianolic acid K and various organic acids. A cytotoxicity evaluation using the Neutral Red Uptake assay showed that the extract had a low toxicity to non-cancerous BALB/3T3 cells. An antiproliferative activity assessment via the MTT assay revealed selective cytotoxicity against Hep G2 hepatocellular carcinoma cells (IC₅₀ = 353.8 ± 21.8 µg/mL) and lung (A549) and prostate (PC-3) carcinoma cell lines. Migration assays and cytopathological evaluations confirmed the significant inhibition of cancer cell proliferation, the suppression of migration and G2/M cell cycle arrest. Flow cytometry revealed considerable increases in apoptotic and necrotic cell populations following treatment with S. aethiopis extract. These findings showed the potential of S. aethiopis as a promising source of bioactive compounds with antioxidant and anticancer properties, supporting its further exploration for therapeutic applications.