C16orf72/HAPSTR1/TAPR1 functions with BRCA1/Senataxin to modulate replication-associated R-loops and confer resistance to PARP disruption.

While the toxicity of PARP inhibitors to cells with defects in homologous recombination (HR) is well established, other synthetic lethal interactions with PARP1/PARP2 disruption are poorly defined. To inform on these mechanisms we conducted a genome-wide screen for genes that are synthetic lethal with PARP1/2 gene disruption and identified C16orf72/HAPSTR1/TAPR1 as a novel modulator of replication-associated R-loops. C16orf72 is critical to facilitate replication fork restart, suppress DNA damage and maintain genome stability in response to replication stress. Importantly, C16orf72 and PARP1/2 function in parallel pathways to suppress DNA:RNA hybrids that accumulate at stalled replication forks. Mechanistically, this is achieved through an interaction of C16orf72 with BRCA1 and the RNA/DNA helicase Senataxin to facilitate their recruitment to RNA:DNA hybrids and confer resistance to PARP inhibitors. Together, this identifies a C16orf72/Senataxin/BRCA1-dependent pathway to suppress replication-associated R-loop accumulation, maintain genome stability and confer resistance to PARP inhibitors.

Regulation of Rad52-dependent replication fork recovery through serine ADP-ribosylation of PolD3.

Although Poly(ADP-ribose)-polymerases (PARPs) are key regulators of genome stability, how site-specific ADP-ribosylation regulates DNA repair is unclear. Here, we describe a novel role for PARP1 and PARP2 in regulating Rad52-dependent replication fork repair to maintain cell viability when homologous recombination is dysfunctional, suppress replication-associated DNA damage, and maintain genome stability. Mechanistically, Mre11 and ATM are required for induction of PARP activity in response to replication stress that in turn promotes break-induced replication (BIR) through assembly of Rad52 at stalled/damaged replication forks. Further, by mapping ADP-ribosylation sites induced upon replication stress, we identify that PolD3 is a target for PARP1/PARP2 and that its site-specific ADP-ribosylation is required for BIR activity, replication fork recovery and genome stability. Overall, these data identify a critical role for Mre11-dependent PARP activation and site-specific ADP-ribosylation in regulating BIR to maintain genome integrity during DNA synthesis.

The integrin ligand SVEP1 regulates GPCR-mediated vasoconstriction via integrins α9ß1 and α4ß1.

BACKGROUND AND PURPOSE: Vascular tone is regulated by the relative contractile state of vascular smooth muscle cells (VSMCs). Several integrins directly modulate VSMC contraction by regulating calcium influx through L-type voltage-gated Ca2+ channels (VGCCs). Genetic variants in ITGA9, which encodes the α9 subunit of integrin α9ß1, and SVEP1, a ligand for integrin α9ß1, associate with elevated blood pressure; however, neither SVEP1 nor integrin α9ß1 has reported roles in vasoregulation. We determined whether SVEP1 and integrin α9ß1 can regulate VSMC contraction. EXPERIMENTAL APPROACH: SVEP1 and integrin binding were confirmed by immunoprecipitation and cell binding assays. Human induced pluripotent stem cell-derived VSMCs were used in in vitro [Ca2+ ]i studies, and aortas from a Svep1+/- knockout mouse model were used in wire myography to measure vessel contraction. KEY RESULTS: We confirmed the ligation of SVEP1 to integrin α9ß1 and additionally found SVEP1 to directly bind to integrin α4ß1. Inhibition of SVEP1, integrin α4ß1 or α9ß1 significantly enhanced [Ca2+ ]i levels in isolated VSMCs to Gαq/11 -vasoconstrictors. This response was confirmed in whole vessels where a greater contraction to U46619 was seen in vessels from Svep1+/- mice compared to littermate controls or when integrin α4ß1 or α9ß1 was inhibited. Inhibition studies suggested that this effect was mediated via VGCCs, PKC and Rho A/Rho kinase dependent mechanisms. CONCLUSIONS AND IMPLICATIONS: Our studies reveal a novel role for SVEP1 and the integrins α4ß1 and α9ß1 in reducing VSMC contractility. This could provide an explanation for the genetic associations with blood pressure risk at the SVEP1 and ITGA9 loci.

The Effectiveness of Biotin (Vitamin B7) Added to the Diet in Improving the Efficiency of Productivity, and Some Physiological Traits for Broiler Chickens (Ross-308) Exposed to Oxidative Stress.

Biotin (B7) acts as an antioxidant, as it inhibits the effect of many free radicals that are naturally formed within the organism's body. This study aimed to determine the effect of adding different concentrations of biotin to the diet of broilers exposed to oxidative stress in improving productive and physiological performance. 180 unsexed Ross-308 one-day age chicks of broiler chickens were used, and they were reared together until 7 days. Then the chicks were randomly distributed into 5 treatments; each treatment included 3 replicates, 12 chicks for each replicate. Oxidative stress was induced by adding 0.5% H2O2 to drinking water. The first treatment, T1 (control), was free from adding B7 or H2O2, and the second treatment (T2): was a positive control treatment free from adding vitamin B7 + water added to it H2O2 at an average of 0.5%. The third treatment (T3): adding 550 micrograms of B7/kg of feed + water added H2O2 at an average of 0.5%. Fourth treatment (T4): 650 micrograms/kg vitamin B7 + water with 0.5% H2O2 added on average. Fifth treatment (T5): 750 micrograms of vitamin B7/kg of feed + 0.5% H2O2 added to the water. The results of adding vitamin B7 to the diet of T4 and T5 birds exposed to oxidative stress showed a significant increase (P<0.05) in the average live body weight, total weight gain and cumulative feed consumption average, and the best cumulative feed conversion ratio for treated birds (T3, T4, T5). In comparison to the other therapies, all additional vitamin B7 treatments demonstrated a significant decrease (P<0.05) in the concentrations of glucose, cholesterol, triglycerides, as well as Malondialdehyde (MDA), and low-density lipoproteins (LDL) and a significant increase (P<0.05) in the concentrations of high-density lipoproteins (HDL) and total protein. The concentration of glutathione peroxidase (GSH-Px) was significantly elevated (P<0.05) in the serum of T5-treated birds compared to all other treatments. We conclude that adding vitamin B7 in different concentrations improved the productivity and some physiological traits of broilers exposed to the induced oxidative stress compared with the negative and positive control treatments.

Effects of Grape Seed Powder on Productive Performance, Lipid Profile and Total Bacteria in Duodenum and Ceca of Broiler Chickens.

Intensive broiler production exposed the birds to several stressors, such as environmental factors, crowding and vaccination. However, when free radical is higher than physiological tolerance cause oxidative stress. This study aimed to investigate the effect of supplementing different levels of grape seed powder to a broiler diet on productive performance, lipid profile and bacterial count of the duodenum and cecum. A total of 180 unsexed one-day-old broiler chicks (Ross 308). Birds were randomly distributed to four dietary treatments (three replicates/treatment, 15 chicks/pen). T1: (control) without addition, T2, T3, and T4, (1, 2, 3) % grape seed powder /kg diet, respectively. Results indicated that final body (42 days of age) and accumulative weight gain, and feed conversion ratio were significantly (P<0.05) better in T2 and T3 (2 and 3) % grape seed powder/kg diet. Blood glucose concentration, cholesterol, Triglyceride, LDL, and MDA were significantly (P<0.05) decreased in T3 and T4 compared with other groups. While there were significant (P<0.05) increases in HDL and Glutathione peroxidase in T3 and T4. There was a significant (P<0.05) decrease in total aerobic bacteria and clone bacteria and a significant increase (P<0.05) in lactobacillus of duodenum and ceca for T3 and T4, respectively. It could be concluded from this study that adding grape seed powder at levels of (2 and 3) % has beneficial effects on productive performance, lipid profile and microbial count of duodenum and ceca.