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Human replication protein A (RPA) is a heterotrimeric (70, 32, and 14 kDa subunits), eukaryotic single-stranded DNA (ssDNA) binding protein required for DNA recombination, repair, and replication. The three subunits of human RPA are composed of six conserved DNA binding domains (DBDs). Deletion and mutational studies have identified a high-affinity DNA binding core in the central region of the 70 kDa subunit, composed of DBDs A and B. To define the roles of each DBD in DNA binding, monomeric and tandem DBD A and B domain chimeras were created and characterized. Individually, DBDs A and B have a very low intrinsic affinity for ssDNA. In contrast, tandem DBDs (AA, AB, BA, and BB) bind ssDNA with moderate to high affinity. The AA chimera had a much higher affinity for ssDNA than did the other tandem DBDs, demonstrating that DBD A has a higher intrinsic affinity for ssDNA than DBD B. The RPA-DNA interface is similar in both DBD A and DBD B. Mutational analysis was carried out to probe the relative contributions of the two domains to DNA binding. Mutation of polar residues in either core DBD resulted in a significant decrease in the affinity of the RPA complex for ssDNA. RPA complexes with pairs of mutated polar residues had lower affinities than those with single mutations. The decrease in affinity observed when polar mutations were combined suggests that multiple polar interactions contribute to the affinity of the RPA core for DNA. These results indicate that RPA-ssDNA interactions are the result of binding of multiple nonequivalent domains. Our data are consistent with a sequential binding model for RPA, in which DBD A is responsible for positioning and initial binding of the RPA complex while DBD A together with DBD B direct stable, high-affinity binding to ssDNA.

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Agrawal DK. SOCS3 promotor hypermethylation and STAT3-NF-B interaction downregulate SOCS3 expression in human coronary artery smooth muscle cells. Am J Physiol Heart Circ Physiol 304: H776 -H785, 2013. First published January 18, 2013 doi:10.1152/ajpheart.00570.2012.-Suppressor of cytokine signaling-3 (SOCS3) is an intracellular negative regulator of cytokine signaling pathway. We recently found significant reduction in SOCS3 expression in coronary artery smooth muscle cells (CASMCs) of atherosclerotic swine and also in vitro cultured cells. Here, we investigated the underlying mechanisms of SOCS3 downregulation by IGF-1 and TNF-␣ in human CASMCs(hCASMCs). We propose that hypermethylation of CpG islands in the SOCS3 promoter is responsible for decrease in SOCS3 expression involving STAT3 and NFkB-p65 interaction. Western blot and qPCR data revealed significant upregulation of SOCS3 (6-to 10-fold) in hCASMC when treated individually with TNF-␣ (100 ng/ml) or IGF-1 (100 ng/ml). However, a significant decrease (5-fold) was observed by the combined treatment with TNF-␣ and IGF-1 compared with individual stimulation. IGF-1 phosphorylated STAT3 and TNF-␣-activated NF-B in hCASMCs. In the nuclear extract of hCASMCs stimulated with both TNF-␣ and IGF-1, there was an interaction between NF-B-p65 and pSTAT3, as determined by co-immunoprecipitation. Knockdown of STAT3 by small interfering RNA abolished SOCS3 expression in response to IGF-1. Methylation-specific PCR confirmed hypermethylation of SOCS3 promoter in hCASMCs stimulated with both TNF-␣ and IGF-1, and this was positively associated with elevated levels of DNA methyltransferase-I (9-to 10-fold). Knockdown of DNMT1 increased SOCS3 expression in IGF-1ϩTNF-␣-stimulated cells. Downregulation of SOCS3 in the presence of both TNF-␣ and IGF-1 in hCASMCs is due to SOCS3 promoter hypermethylation involving STAT3-NFkBp65 interaction. Because TNF-␣ and IGF-1 are released due to mechanical injury during coronary intervention, hypermethylation of SOCS3 gene could be an underlying mechanism of intimal hyperplasia and restenosis. cell signaling; cytokines; growth factors; hypermethylation; intimal hyperplasia; smooth muscle cells; suppressor of cytokine signaling 3; signal transducer and activator of transcription

Preparative-scale biotransformation of quercetin (1), fisetin (7), and (+)-catechin (12) with Streptomyces griseus (ATCC 13273) resulted in the isolation and characterization of nine known hydroxylated and/or methylated (2--6, 8, 9, 11, 13a) metabolites and two previously unknown (10 and 14) metabolites. S.griseus catalyzed aromatic hydroxylations of rings A and B of quercetin and fisetin. Mono- and dimethoxy ring-B metabolites were obtained with all three substrates. Methylation appeared to occur only when catechol functional groups were present. Metabolite structures were established by FABMS, EIMS, and 1D and 2D NMR analysis.

The eukaryotic single-stranded DNA-binding protein, replication protein A (RPA), is essential in DNA metabolism and is phosphorylated in response to DNA-damaging agents. Rad52 and RPA participate in the repair of double-stranded DNA breaks (DSBs). It is known that human RPA and Rad52 form a complex, but the molecular mass, stoichiometry, and exact role of this complex in DSB repair are unclear. In this study, absolute molecular masses of individual proteins and complexes were measured in solution using analytical size-exclusion chromatography coupled with multiangle light scattering, the protein species present in each purified fraction were verified via sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western analyses, and the presence of biotinylated ssDNA in the complexes was verified by chemiluminescence detection. Then, employing UV cross-linking, the protein partner holding the ssDNA was identified. These data show that phosphorylated RPA promoted formation of a complex with monomeric Rad52 and caused the transfer of ssDNA from RPA to Rad52. This suggests that RPA phosphorylation may regulate the first steps of DSB repair and is necessary for the mediator function of Rad52. Double-strand breaks (DSBs) 1 in chromosomal DNA are efficiently repaired by homologous recombination (HR) (1). The RAD52 epistasis group of proteins, including Rad51, Rad52, and replication protein A (RPA), performs the repair of DSBs by HR (2, 3). Studies with Saccharomyces cerevisiae proteins (4-6) and with human proteins (7-10) demonstrated the importance of specific protein-protein contacts in controlling the functional interactions among Rad51, Rad52, and RPA. Rad52 acts as a mediator between RPA-coated ssDNA and Rad51 (11-13), and a similar function is also proposed for human BRCA2 protein (14). However, the molecular mechanisms for the delivery of Rad51 by mediators to RPA-coated ssDNA are not known in detail.RPA is the ubiquitous eukaryotic single-stranded DNA (ssDNA) binding protein that is composed of three subunits that have been named for their molecular masses in kilodaltons as RPA70, RPA32, and RPA14 (15,16). The heterotrimer is the main biological form of RPA (17, 18) and is very stable when purified (19). RPA binds ssDNA more tightly than RNA or double-stranded DNA (dsDNA), prefers purines over pyrimidines (16), and has a 25-30-nucleotide footprint (20). RPA is composed of six oligonucleotide/oligosaccharide binding (OB) domains that bind ssDNA and/or participate in specific proteinprotein interactions (21). RPA is also known to undergo a significant conformational change upon binding DNA (22, 23) that appears to alter RPA's structure in a way that facilitates interactions with other proteins and ssDNA.The exact signal(s) for the presence of single-or doublestranded DNA breaks in a cell is still poorly understood, but the ssDNA-RPA complex appears to be an important component (24). Once DSBs are sensed, several downstream HR repair effector proteins are phosphorylated (25). RPA is phospho...

Aims The growth and differentiation of cells is regulated by cytokines by binding to cell-surface receptors and activating intracellular signal transduction cascade. Suppressor of cytokine signaling (SOCS)-3 is a negative regulator of cytokines. In this study we examined the expression of SOCS3 in porcine coronary artery smooth muscle cells (PCASMCs) in vitro and in proliferating smooth muscle cells of neointimal lesions after coronary artery intervention in a swine model. Methods and Results PCASMCs were cultured and stimulated with TNF-α and/or IGF-1 individually or in combination. Protein expression of SOCS-3 was examined using Western blot. For in vivo studies, six female Yucatan miniswine were fed with special high cholesterol diet for 8 months. At 4 months of high cholesterol diet, animals underwent coronary balloon angioplasty. At the end of 8 months animals were euthanized, coronary arteries were isolated and morphological and histological studies were performed. Western blot data revealed significantly high SOCS-3 expression in PCASMCs in the presence of either TNF-α or IGF-1 (5–6 fold) alone. However, in the presence of both TNF-α and IGF-1 the SOCS-3 expression was significantly decreased (4–5 fold). Results from morphological studies including, H&E and Masson’s trichrome stain showed typical lesions with significant neointimal proliferation. Histological evaluation showed expression of smooth muscle α-actin and significantly increased proliferating cell nuclear antigen (PCNA) in neointimal lesion. Interestingly, there was significantly decreased expression of SOCS3 in smooth muscle cells of neointima as compared to control. Conclusions These data suggest that SOCS3 expression is decreased in proliferating smooth muscle cells of neointimal lesions. This leads to uncontrolled growth of vascular smooth muscle cells in injured arteries leading to restenosis. Therefore, local delivery of SOCS3 gene at the site of injury after coronary artery intervention could regulate the proliferation of vascular smooth muscle cells and help in preventing the neointimal hyperplasia and restenosis.

BackgroundMyocardial recovery with left ventricular assist device (LVAD) therapy is highly variable and difficult to predict. Next generation ribonucleic acid (RNA) sequencing is an innovative, rapid, and quantitative approach to gene expression profiling in small amounts of tissue. Our primary goal was to identify baseline transcriptional profiles in non-ischemic cardiomyopathies that predict myocardial recovery in response to LVAD therapy. We also sought to verify transcriptional differences between failing and non-failing human hearts.MethodsRNA was isolated from failing (n = 16) and non-failing (n = 8) human hearts. RNA from each patient was reverse transcribed and quantitatively sequenced on the personal genome machine (PGM) sequencer (Ion torrent) for 95 heart failure candidate genes. Coverage analysis as well as mapping the reads and alignment was done using the Ion Torrent Browser Suite™. Differential expression analyses were conducted by empirical analysis of digital gene expression data in R (edgeR) to identify differential expressed genes between failing and non-failing groups, and between responder and non-responder groups respectively. Targeted cardiac gene messenger RNA (mRNA) expression was analyzed in proportion to the total number of reads. Gene expression profiles from the PGM sequencer were validated by performing RNA sequencing (RNAseq) with the Illumina Hiseq2500 sequencing system.ResultsThe failing sample population was 75% male with an average age of 50 and a left ventricular ejection fraction (LVEF) of 16%. Myosin light chain kinase (MYLK) and interleukin (IL)-6 genes expression were significantly higher in LVAD responders compared to non-responders. Thirty-six cardiac genes were expressed differentially between failing and non-failing hearts (23 decreased, 13 elevated). MYLK, Beta-1 adrenergic receptor (ADRB1) and myosin heavy chain (MYH)-6 expression were among those significantly decreased in failing hearts compared to non-failing hearts. Natriuretic peptide B (NPPB) and IL-6 were significantly elevated. Targeted gene expression profiles obtained from the Ion torrent PGM sequencer were consistent with those obtained from Illumina HiSeq2500 sequencing system.ConclusionsHeart failure is associated with a network of transcriptional changes involving contractile proteins, metabolism, adrenergic receptors, protein phosphorylation, and signaling factors. Myocardial MYLK and IL-6 expression are positively correlated with ejection fraction (EF) response to LVAD placement. Targeted RNA sequencing of myocardial gene expression can be utilized to predict responders to LVAD therapy and to better characterize transcriptional changes in human heart failure.