Repression Of DNA Replication Research Articles

Discovery proteomics defines androgen-regulated glycoprotein networks in prostate cancer cells, as well as putative biomarkers of prostatic diseases

Supraphysiologic androgen (SPA) inhibits cell proliferation in prostate cancer (PCa) cells by transcriptional repression of DNA replication and cell-cycle genes. In this study, quantitative glycoprotein profiling identified androgen-regulated glycoprotein networks associated with SPA-mediated inhibition of PCa cell proliferation, and androgen-regulated glycoproteins in clinical prostate tissues. SPA-regulated glycoprotein networks were enriched for translation factors and ribosomal proteins, proteins that are known to be O-GlcNAcylated in response to various cellular stresses. Thus, androgen-regulated glycoproteins are likely to be targeted for O-GlcNAcylation. Comparative analysis of glycosylated proteins in PCa cells and clinical prostate tissue identified androgen-regulated glycoproteins that are differentially expressed prostate tissues at various stages of cancer. Notably, the enzyme ectonucleoside triphosphate diphosphohydrolase 5 was found to be an androgen-regulated glycoprotein in PCa cells, with higher expression in cancerous versus non-cancerous prostate tissue. Our glycoproteomics study provides an experimental framework for characterizing androgen-regulated proteins and glycoprotein networks, toward better understanding how this subproteome leads to physiologic and supraphysiologic proliferation responses in PCa cells, and their potential use as druggable biomarkers of dysregulated AR-dependent signaling in PCa cells.

Multipath effects of berberine on peach Brown rot fungus Monilinia fructicola

The brown rot disease caused by fungus Monilinia fructicola severely reduces the yield of peach and other stone fruits. Earlier, we found that berberine (BBR), one of isoquinoline alkaloids, strongly halts the growth of M. fructicola. However, the underlying mechanisms remain unclear. Here we report that BBR inhibits M. fructicola at multiple levels. Scanning electronic microscope (SEM) analysis of BBR-treated M. fructicola revealed morphological abnormality of spores and hyphae. Enzyme activity assay showed BBR's significant inhibition on the activities of enzymes succinate dehydrogenase (SDH), malate dehydrogenase (MDH) and ATPase in mitochondrion, indicating that BBR impedes mitochondrial functions. Furthermore, transcriptomic analysis of BBR-induced M. fructicola revealed that most differentially expressed genes were involved in MAP kinase activity, activation of MAPKK activity, and ADP binding. Overall, these results indicate that BBR inhibits M. fructicola through multipath mechanisms, including destruction on cells, interference of mitochondrial functions, and repression of DNA replication and gene expression.

Rif1 inhibits replication fork progression and controls DNA copy number in Drosophila.

Control of DNA copy number is essential to maintain genome stability and ensure proper cell and tissue function. In Drosophila polyploid cells, the SNF2-domain-containing SUUR protein inhibits replication fork progression within specific regions of the genome to promote DNA underreplication. While dissecting the function of SUUR's SNF2 domain, we identified an interaction between SUUR and Rif1. Rif1 has many roles in DNA metabolism and regulates the replication timing program. We demonstrate that repression of DNA replication is dependent on Rif1. Rif1 localizes to active replication forks in a partially SUUR-dependent manner and directly regulates replication fork progression. Importantly, SUUR associates with replication forks in the absence of Rif1, indicating that Rif1 acts downstream of SUUR to inhibit fork progression. Our findings uncover an unrecognized function of the Rif1 protein as a regulator of replication fork progression.

Ailanthone inhibits non-small cell lung cancer cell growth through repressing DNA replication via downregulating RPA1

Background:The identification of bioactive compounds from Chinese medicine plays a crucial role in the development of novel reagents against non-small lung cancer (NSCLC).Methods:High throughput screening assay and analyses of cell growth, cell cycle, apoptosis, cDNA microarray, BrdU incorporation and gene expression were performed.Results:Ailanthone (Aila) suppressed NSCLC cell growth and colony formation in vitro and inhibited NSCLC tumour growth in subcutaneously xenografted and orthotopic lung tumour models, leading to prolonged survival of tumour-bearing mice. Moreover, Aila induced cell cycle arrest in a dose-independent manner but did not induce apoptosis in all NSCLC cells. Furthermore, 1222 genes were differentially expressed upon Aila administration, which were involved in 21 signal pathways, such as DNA replication. In addition, Aila dose-dependently decreased BrdU incorporation and downregulated the expression of replication protein A1 (RPA1).Conclusions:Aila inhibited the growth of NSCLC cells through the repression of DNA replication via downregulating RPA1, rather than through cell cycle arrest and apoptosis. Our findings suggested that Aila could be used as a promising therapeutic candidate for NSCLC patients.

Inhibition of DNA methyltransferase inhibits DNA replication.

Ectopic expression of DNA methyltransferase transforms vertebrate cells, and inhibition of DNA methyltransferase reverses the transformed phenotype by an unknown mechanism. We tested the hypothesis that the presence of an active DNA methyltransferase is required for DNA replication in human non-small cell lung carcinoma A549 cells. We show that the inhibition of DNA methyltransferase by two novel mechanisms negatively affects DNA synthesis and progression through the cell cycle. Competitive polymerase chain reaction of newly synthesized DNA shows decreased origin activity at three previously characterized origins of replication following DNA methyltransferase inhibition. We suggest that the requirement of an active DNA methyltransferase for the functioning of the replication machinery has evolved to coordinate DNA replication and inheritance of the DNA methylation pattern.