ABSTRACT
DNA polymerase λ (DNA pol λ) is the only reported X-family DNA polymerases in plants and has been shown to play a significant role in dry quiescent seeds, growth, development and nuclear DNA repair. cDNA for DNA pol λ has been reported in Arabidopsis and japonica rice cultivar and has been characterized from E. coli expressed protein, but very little is known about its activity at protein level in plants. The enzymatic activity of DNA pol λ was studied in dry, imbibed and during different germination stages of indica rice IR-8 (salt sensitive) by in-gel activity assay to determine its physiological role in important stages of growth and development. The upstream sequence was also analyzed using plantCARE database and was found to contain several cis-acting elements, including light responsive elements, dehydration responsive elements, Myb binding sites, etc. Hence, 4-day-old germinating seedlings of IR29, a salt-sensitive, but high yielding indica rice cultivar and Nonabokra, a salt-tolerant, but low yielding cultivar were treated with water (control) or 250 mM NaCl or 20% polyethyleneglycol-6000 for 4 and 8 h. The protein was analyzed by in vitro DNA pol λ activity assay, in-gel activity assay and Western blot analysis. DNA pol λ was not detected in dry seeds, but enhanced after imbibition and detectable from low level to high level during subsequent germination steps. Both salinity and dehydration stress led to the enhancement of the activity and protein level of DNA pol λ, as compared to control tissues. This is the first evidence of the salinity or dehydration stress induced enhancement of DNA pol λ activity in the plumules of rice (Oryza sativa L.) cultivars.
Subject(s)
DNA-Directed DNA Polymerase/analysis , DNA-Directed DNA Polymerase/physiology , Germination/genetics , Oryza/genetics , Oryza/growth & development , Salinity , Seeds/growth & development , Sodium Chloride , Stress, PhysiologicalABSTRACT
Objective To study the effects of Alternariol(AOH) on DNA polymerase ?(DNA POL?)expression in NIH3T3 cells.Methods RT-PCR,Immunocytochemistry and Western blot were used to detected mRNA and the protein levels of DNA POL? in NIH3T3 cell line induced by AOH.Results The expression of DNA POL? in NIH3T3 cells contaminated by AOH was significantly higher than that in the control group(P
ABSTRACT
Objective To establish human lung adenocarcinoma multidrug resistance cell lines in vitro,observe their biological characteristics,and investigate the mRNA expressions of DNA pol?,mdr 1,mrp1,GST-?,lrp and topo Ⅱ genes.Methods Paclitaxel-resistant cell lines(A549/TXL20) were established in vitro by exposure to stepwise increased concentrations of the drug in a cell culture medium.Biological morphology and cell cycles were analyzed by morphometry and flow cytometry.The chemoresistance indexes of cells were measured by methyl tetrazolium assay.Evaluation of growth and in vitro drug sensitivity were performed.RT-PCR was employed to analyze the mRNA expressions of the DNA pol?,mdr 1,mrp1,GST-?,lrp,and topo Ⅱ genes.Results ① Compared with parent cells,the resistant sublines had a lower confluent density.They were smaller and mixed with giant cells in different sizes and with different numbers of nucleoli,and the growth property of A549/TXL20 did not change significantly compared with A549 cell lines.② The resistant cells,A549/TXL20,were 19.3 times more resistant to paclitaxel and 67.4 times more resistant to cisplatin than the parent cells,and also demonstrated cross-resistance to mitomycin,vinblastine,and 5-fluouracil(5-FU). ③ Compared with the A549 celllines,an unreasonably higher level of drug resistance and lower drug concentration was detected in A549/TXL20 cells after exposure to the drug in the culture medium.④ The mRNA expression level of DNA pol?,mdr1,GST-?,mrp1 andlrp genes in A549/TXL20 cells was significantly higher than that in A549 cell lines(P