Identification of indole-3-carboxylic acids as non-ATP-competitive Polo-like kinase 1 (Plk1) inhibitors.

A series of indole-3-carboxylic acids were designed as novel small molecular non-ATP-competitive Plk1 inhibitors. The designed compounds were synthesized and evaluated. Most of the targeted compounds showed potent Plk1 inhibitory activities and anti-proliferative characters. Particularly, 4f and 4g showed Plk1 inhibitory activity with IC50 values of 0.41 and 0.13µM, which were about 5 and 17 times more potent compared to thymoquinone, respectively. Compound 4g also showed inhibitory activity to HeLa and MCF-7 cell lines with IC50 values of 0.72 and 1.15µM, which was almost 3 and 4 times more potent than thymoquinone. Study of mechanism of action suggested that 4g was an ATP-independent and substrate-dependent Plk1 inhibitor. Moreover, 4g showed excellent Plk1 inhibitory selectivity against Plk2 and Plk3. Fluorescein isothiocyanate Annexin V/propidium iodide (PI) double-staining assay and western-blot results indicate that induction of apoptosis by 4g is involved in its anti-tumor activity. This study may provide a support for further optimization of non-ATP-competitive Plk1 inhibitors.

Design, synthesis, and evaluation of non-ATP-competitive small-molecule Polo-like kinase 1 (Plk1) inhibitors.

A series of small-molecule Plk1 inhibitors targeting the substrate-binding pocket were designed through rational drug design for the first time. The designed compounds were synthesized and their activities were evaluated in vitro. Some of the targeted compounds showed potent Plk1 inhibitory activities and anti-proliferative characters. Particularly, 5i showed Plk1 inhibitory activity with an IC50 value of 0.68 µM. Compound 5i also showed cell growth inhibitory activity on HeLa cells with an IC50 value of 0.51 µM, which is about four times more potent compared to thymoquinone. The mechanism of action suggested that 5i was an ATP-independent and substrate-dependent Plk1 inhibitor. Compound 5i demonstrated excellent Plk1 inhibitory selectivity against Plk2, Plk3, and five serine/threonine and tyrosine kinases. Our discovery and structure-activity relationship study may provide useful lead compounds for further optimization of non-ATP-competitive Plk1 inhibitors.

Isolation of GPD promoter from Tremella fuciformis and driving expression of EGFP gene.

Glyceraldehyde-3-phosphate dehydrogenase (GPD) cDNA was cloned by RT-PCR using total RNA from Tremella fuciformis as template with a pair of degenerate primers. Then, a 500-bp 5'-upstream promoter region of the gene encoding GPD from T. fuciformis genomic DNA was isolated by thermal asymmetric interlaced PCR. The cloned promoter was fused to 5'-upstream of enhanced green fluorescent protein gene to construct T. fuciformis expression vector pCB-TEGFP with hygromycin gene as a selectable marker. Electroporation was performed to transfer plasmid DNA of pCB-TEGFP into yeast-like conidia from T. fuciformis. Molecular evidence, including PCR analysis, fluorescence detection, fluorescence spectra assay, and SDS-PAGE, indicated that the EGFP gene had been integrated into the genome of transgenic T. fuciformis strains and was expressed successfully. The results also showed that this promoter could be used to carry out regulated expression of heterologous gene products in T. fuciformis.