We previously identified a mammalian Set1A complex analogous to the yeast Set1/COMPASS histone H3-Lys4 methyltransferase complex (Lee, J. . Both Set1A and Set1B are widely expressed. Inducible expression of the carboxyl terminus of either Set1A or Set1B decreases steady-state levels of both endogenous Set1A and Set1B protein, but does not alter the expression of the non-catalytic components of the Set1 complexes. A 123-amino acid fragment upstream of the Set1A SET domain is necessary for interaction with CFP1, Ash2, Rbbp5, and Wdr5. This protein domain is also required to mediate feedback inhibition of Set1A and Set1B expression, which is a consequence of reduced Set1A and Set1B stability when not associated with the methyltransferase complex. Confocal microscopy reveals that Set1A and Set1B each localize to a largely non-overlapping set of euchromatic nuclear speckles, suggesting that Set1A and Set1B each bind to a unique set of target genes and thus make non-redundant contributions to the epigenetic control of chromatin structure and gene expression.

XPA, XPC-hHR23B, RPA, and TFIIH all are the damage recognition proteins essential for the early stage of nucleotide excision repair. Nonetheless, it is not clear how these proteins work together at the damaged DNA site. To get insight into the molecular mechanism of damage recognition, we carried out a comprehensive analysis on the interaction between damage recognition proteins and their assembly on damaged DNA. XPC physically interacted with XPA, but failed to stabilize the XPA-damaged DNA complex. Instead, XPC-hHR23B was effectively displaced from the damaged DNA by the combined action of RPA and XPA. A mutant RPA lacking the XPA interaction domain failed to displace XPChHR23B from damaged DNA, suggesting that XPA and RPA cooperate with each other to destabilize the XPChHR23B-damaged DNA complex. Interestingly, the presence of hHR23B significantly increased RPA/XPA-mediated displacement of XPC from damaged DNA, suggesting that hHR23B may modulate the binding of XPC to damaged DNA. Together, our results suggest that damage recognition occurs in a multistep process such that XPC-hHR23B initiates damage recognition, which was replaced by combined action of XPA and RPA. XPA and RPA, once forming a complex at the damage site, would likely work with TFIIH, XPG, and ERCC1-XPF for dual incision.

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In this study, we successfully synthesized d-α-tocopheryl polyethylene glycol 2000 succinate (TPGS2k) and prepared TPGS2k-modified poly(lactic-co-glycolic acid) nanoparticles (TPGS2k/PLGA NPs) loaded with 7-ethyl-10-hydroxycamptothecin (SN-38), designated TPGS2k/PLGA/SN-38 NPs. Characterization measurements showed that TPGS2k/PLGA/SN-38 NPs displayed flat and spheroidal particles with diameters of 80-104 nm. SN-38 was encapsulated in TPGS2k emulsified PLGA NPs with the entrapment efficiency and loading rates of SN-38 83.6 and 7.85%, respectively. SN-38 could release constantly from TPGS2k/PLGA/SN-38 NPs in vitro. TPGS2k/PLGA/SN-38 NPs induced significantly higher cytotoxicity on A549 cells and the multidrug resistance (MDR) cell line (A549/DDP cells and A549/Taxol cells) compared with free SN-38. Further studies on the mechanism of the NPs in increasing the death of MDR cells showed that following the SN-38 releasing into cytoplasm the remaining TPGS2k/PLGA NPs could reverse the P-gp mediated MDR via interfering with the structure and function of mitochondria and rather than directly inhibiting the enzymatic activity of P-gp ATPase. Therefore, TPGS2k/PLGA NPs can reduce the generation of ATP and the release of energy for the requisite of P-gp efflux transporters. The results indicated that TPGS2k/PLGA NPs could become the nanopharmaceutical materials with the capability to reversal MDR and improve anticancer effects of some chemotherapy drugs as P-gp substrates.

The present study aimed to investigate the effect of apigenin on glioma cells and to explore its potential mechanism. U87 human glioma cells treated with apigenin were used in the current study. Cell Counting Kit‑8 solution and Annexin V-fluorescein isothiocyanate/propidium iodide Apoptosis Detection kit were used to analyze the effect of apigenin on U87 cell viability and apoptotic cell death. Reverse transcription‑quantitative polymerase chain reaction analysis was also used to determine microRNA‑16 (miR‑16) and MMP‑9 gene expression levels. Nuclear factor‑κB (NF‑κB) and B‑cell CLL/lymphoma 2 (BCL2) protein expression levels were determined using western blot analysis. An anti‑miR‑16 plasmid was constructed and transfected into U87 cells. The current study demonstrated that apigenin significantly decreased cell viability and induced apoptotic cell death of U87 cells in a dose‑dependent manner. Additionally, it was demonstrated that apigenin significantly increased miR‑16 levels, suppressed BCL2 protein expression and suppressed the NF‑κB/MMP9 signaling pathway in U87 cells. Furthermore, downregulation of miR‑16 using the anti‑miR‑16 plasmid reversed the effect of apigenin on cell viability, BCL2 protein expression and the NF‑κB/MMP‑9 pathway in U87 cells. The results of the present study suggested that apigenin inhibits glioma cell growth through promoting miR‑16 and suppression of BCL2 and NF-κB/MMP-9. In conclusion, the present study demonstrated the potential anticancer effects of apigenin on glioma cells.