The same mammalian replicon yields distinct recombination products in different cell lines.

We have observed previously that some chimeric replicons inclusive of a partly duplicated polyomavirus (Py) genome yield unit-length Py DNA (P155) at high frequency when transfected into normal or Py-transformed mouse cells. We demonstrate here that one such replicon generates either P155 or illegitimate recombination products in other mouse cells, transformed by simian virus 40. Use of the polymerase chain reaction indicates that each of the illegitimate products carried a different deletion, but that all deletions mapped within a rather well defined portion of the precursor replicon. Thus, these products were organized as if two hotspots for recombination existed in the Py late-coding region, one being located within or near one of the duplicated sequences characteristic of the chimeric replicon. Since this particular hotspot has already been shown to be involved in the generation of P155, the data reported here could indicate that a single recombination mechanism can yield either homologous (P155) or illegitimate products. How the DNA interacts with certain proteins, such as papovavirus large tumor antigen, could explain why one or the other type of product is formed.     

Molecular basis for the defective expression of the mouse Ew17 beta gene

Four of the eleven independent H-2 haplotypes of inbred mouse strains and approximately 15% of wild mouse chromosomes 17 fail to express the E alpha E beta class II histocompatibility (Ia) Ag. These E- haplotypes are defective in the expression of the E alpha and/or the E beta chain. None of the E beta defects has previously been described at the molecular level. In this study, we report the molecular basis for the defective expression of the E beta gene from the w17 haplotype of the H-2 congenic strain B10.CAS2, derived from wild Mus musculus castaneus. Comparison of the Ew17 beta genomic sequence to those of the functional Eb beta and Ed beta genes reveals a single base insertion in the RNA donor splice site of the first intron. By DNA shuffling, we have corrected the single base mutation, and we show by FACS analysis and 2-D PAGE of immunoprecipitates that the corrected Ew17 beta is expressed in L cells when co-transfected with an Ed alpha gene. Conversely, an Eb beta gene construct containing the mutant RNA splice site from Ew17 beta is not expressed. We conclude that the single base insertion in the first RNA splice donor site is the sole molecular defect in the Ew17 beta gene.     

Multiple components of the spliceosome regulate Mcl1 activity in neuroblastoma

Cancer treatments induce cell stress to trigger apoptosis in tumor cells. Many cancers repress these apoptotic signals through alterations in the Bcl2 proteins that regulate this process. Therapeutics that target these specific survival biases are in development, and drugs that inhibit Bcl2 activities have shown clinical activity for some cancers. Mcl1 is a survival factor for which no effective antagonists have been developed, so it remains a principal mediator of therapy resistance, including to Bcl2 inhibitors. We used a synthetic-lethal screening strategy to identify genes that regulate Mcl1 survival activity using the pediatric tumor neuroblastoma (NB) as a model, as a large subset are functionally verified to be Mcl1 dependent and Bcl2 inhibitor resistant. A targeted siRNA screen identified genes whose knockdown restores sensitivity of Mcl1-dependent NBs to ABT-737, a small molecule inhibitor of Bcl2, BclXL and BclW. Three target genes that shifted the ABT-737 IC50 >1 log were identified and validated: PSMD14, UBL5 and PRPF8. The latter two are members of a recently characterized subcomplex of the spliceosome that along with SART1 is responsible for non-canonical 5′-splice sequence recognition in yeast. We showed that SART1 knockdown similarly sensitized Mcl1-dependent NB to ABT-737 and that triple knockdown of UBL5/PRPF8/SART1 phenocopied direct MCL1 knockdown, whereas having no effect on Bcl2-dependent NBs. Both genetic spliceosome knockdown or treatment with SF3b-interacting spliceosome inhibitors like spliceostatin A led to preferential pro-apoptotic Mcl1-S splicing and reduced translation and abundance of Mcl1 protein. In contrast, BN82865, which inhibits the second transesterification step in terminal spliceosome processing, did not have this effect. These findings demonstrate a prominent role for the spliceosome in mediating Mcl1 activity and suggest that drugs that target either the specific UBL5/PRPF8/SART1 subcomplex or SF3b functions may have a role as cancer therapeutics by attenuating the Mcl1 survival bias present in numerous cancers.     

Antioxidant Activity of a New Xanthone Derivative from Aspidistra Letreae: In Vitro and In Silico Studies

A new xanthone derivative, aspidxanthone A ( 1 ), and three known compounds ((2S)-1-(β-D-galactopyranosyloxy)-3-(hexadecanoyloxy)propan-2-yl (9Z,12Z)-octadeca-9,12-dienoate ( 2 ), (25S)-spirostane-1β,3α,5β-triol ( 3 ), and asparenyldiol ( 4 )) were isolated from the whole of the endemic species Aspidistra letreae in Vietnam. Their structures were elucidated by means of extensive spectroscopic analyses and comparison with published data. In this study, we report the isolation and structure elucidation of a new compound aspidxanthone A, antioxidant activities of the extract and isolates 1 – 4 , and in silico molecular docking of aspidxanthone A. The ethyl acetate extract had good antioxidant activity with an IC₅₀ value of 26.3 μg mL⁻¹. Among the isolates, aspidxanthone A exhibited DPPH reduction activity with an IC₅₀ value of 11.2 μM, which is in the same range as that of the positive control, ascorbic acid. The mechanism of action of aspidxanthone A on the tyrosinase and xanthine oxidase proteins have been clarified by in silico studies.     

Determining the Presence of Superantigens in Coagulase Negative Staphylococci from Humans

Superantigens (SAgs) are important virulence factors in S. aureus. Recent studies identified their presence in animal coagulase-negative staphylococci (CNS). The emergence of human-associated SAg⁺ CNS would mark a prodigious shift in virulence capabilities. We examined CNS isolates from healthy human nares and diseased individuals, and determined that no known SAgs were present.     

Room Temperature Processed Highly Efficient Large‐Area Polymer Solar Cells Achieved with Molecular Engineering of Copolymers

The room temperature (RT) processability of the photoactive layers in polymer solar cells (PSCs) from halogen‐free solvent along with their highly reproducible power conversion efficiencies (PCEs) and intrinsic thickness tolerance are extremely desirable for the large‐area roll‐to‐roll (R2R) production. However, most of the photoactive materials in PSCs require elevated processing temperatures due to their strong aggregation, which are unfavorable for the industrial R2R manufacturing of PSCs. These limiting factors for the commercialization of PSCs are alleviated by synthesizing random terpolymers with components of (2‐decyltetradecyl)thiophen‐2‐yl)naphtho[1,2‐c:5,6‐c′]bis[1,2,5]thiadiazole and bithiophene substituted with methyl thiophene‐3‐carboxylate (MTC). In contrast to the temperature‐dependent PNTz4T polymer, the resulting random terpolymers (PNTz4T‐MTC) show better solubility, slightly reduced crystallinity and aggregation, and weaker intermolecular interaction, thus enabling PNTz4T‐MTC to be processed at RT from a halogen‐free solvent. Particularly, the PNTz4T‐5MTC‐based photoactive layer exhibits an excellent PCE of 9.66%, which is among the highest reported PCEs for RT and ecofriendly halogen‐free solvent processed fullerene‐based PSCs, and a thickness tolerance with a PCE exceeding 8% from 100 to 520 nm. Finally, large‐area modules fabricated with the PNTz4T and PNTz4T‐5MTC polymer have shown 4.29% and 6.61% PCE respectively, with an area as high as 54.45 cm² in air.