Boubriak Ivan, Ng Wooi Loon, DasSarma Priya, DasSarma Shiladitya, Crowley David J, McCready Shirley J
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Institute of Cell Biology and Genetic Engineering, UAS, 148 Zabolotnogo Street, Kiev, 03143, Ukraine.
Saline Syst. 2008 Aug 29;4:13. doi: 10.1186/1746-1448-4-13.
Most studies of the transcriptional response to UV radiation in living cells have used UV doses that are much higher than those encountered in the natural environment, and most focus on short-wave UV (UV-C) at 254 nm, a wavelength that never reaches the Earth's surface. We have studied the transcriptional response of the sunlight-tolerant model archaeon, Halobacterium sp. NRC-1, to low doses of mid-wave UV (UV-B) to assess its response to UV radiation that is likely to be more biologically relevant.
Halobacterium NRC-1 cells were irradiated with UV-B at doses equivalent to 30 J/m2 and 5 J/m2 of UV-C. Transcriptional profiling showed that only 11 genes were up-regulated 1.5-fold or more by both UV-B doses. The most strongly up-regulated gene was radA1 (vng2473), the archaeal homologue of RAD51/recA recombinase. The others included arj1 (vng779) (recJ-like exonuclease), top6A (vng884) and top6B (vng885) (coding for Topoisomerase VI subunits), and nrdJ (vng1644) (which encodes a subunit of ribonucleotide reductase). We have found that four of the consistently UV-B up-regulated genes, radA1 (vng2473), vng17, top6B (vng885) and vng280, share a common 11-base pair motif in their promoter region, TTTCACTTTCA. Similar sequences were found in radA promoters in other halophilic archaea, as well as in the radA promoter of Methanospirillum hungatei. We analysed the transcriptional response of a repair-deficient DeltauvrA (vng2636) DeltauvrC (vng2381) double-deletion mutant and found common themes between it and the response in repair proficient cells.
Our results show a core set of genes is consistently up-regulated after exposure to UV-B light at low, biologically relevant doses. Eleven genes were up-regulated, in wild-type cells, after two UV-B doses (comparable to UV-C doses of 30 J/m2 and 5 J/m2), and only four genes were up-regulated by all doses of UV-B and UV-C that we have used in this work and previously. These results suggest that high doses of UV-C radiation do not necessarily provide a good model for the natural response to environmental UV. We have found an 11-base pair motif upstream of the TATA box in four of the UV-B up-regulated genes and suggest that this motif is the binding site for a transcriptional regulator involved in their response to UV damage in this model archaeon.
大多数关于活细胞对紫外线辐射转录反应的研究使用的紫外线剂量远高于自然环境中遇到的剂量，并且大多数研究集中在254nm的短波紫外线（UV-C）上，该波长从未到达地球表面。我们研究了耐阳光的古菌模式菌株嗜盐杆菌属NRC-1对低剂量中波紫外线（UV-B）的转录反应，以评估其对可能更具生物学相关性的紫外线辐射的反应。
用相当于30J/m²和5J/m² UV-C剂量的UV-B照射嗜盐杆菌NRC-1细胞。转录谱分析表明，两种UV-B剂量均使仅11个基因上调1.5倍或更多。上调最强烈的基因是radA1（vng2473），即RAD51/recA重组酶的古菌同源物。其他基因包括arj1（vng779）（recJ样核酸外切酶）、top6A（vng884）和top6B（vng885）（编码拓扑异构酶VI亚基）以及nrdJ（vng1644）（编码核糖核苷酸还原酶的一个亚基）。我们发现，在UV-B持续上调的四个基因radA1（vng2473）、vng17、top6B（vng885）和vng280在其启动子区域共享一个共同的11个碱基对基序TTTCACTTTCA。在其他嗜盐古菌的radA启动子以及Hungate甲烷螺菌的radA启动子中也发现了类似序列。我们分析了修复缺陷型DeltauvrA（vng2636）DeltauvrC（vng2381）双缺失突变体的转录反应，并发现了它与修复 proficient 细胞反应之间的共同主题。
我们的结果表明，在暴露于低剂量、具有生物学相关性的UV-B光后，一组核心基因持续上调。在野生型细胞中，两种UV-B剂量（相当于30J/m²和5J/m²的UV-C剂量）后有11个基因上调，而在我们这项工作及之前使用的所有UV-B和UV-C剂量下，只有四个基因上调。这些结果表明，高剂量的UV-C辐射不一定能为对环境紫外线的自然反应提供良好模型。我们在四个UV-B上调基因的TATA框上游发现了一个11个碱基对的基序，并表明该基序是参与该模式古菌对紫外线损伤反应的转录调节因子的结合位点。
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