Deitsch Erin, Hibbard Erin M, Petersen Jason L
Center for Biological Control and Analysis by Applied Photonics (BCAAP), South Dakota State University, Brookings, SD, USA; Research and Development, Sioux Falls Veterans Affairs Health Care System, Sioux Falls, SD, USA.
Research and Development, Sioux Falls Veterans Affairs Health Care System, Sioux Falls, SD, USA.
DNA Repair (Amst). 2016 Jan;37:33-42. doi: 10.1016/j.dnarep.2015.11.003. Epub 2015 Nov 19.
Nucleotide excision repair (NER) is a key pathway for removing DNA damage that destabilizes the DNA double helix. During NER a protein complex coordinates to cleave the damaged DNA strand on both sides of the damage. The resulting lesion-containing oligonucleotide is displaced from the DNA and a replacement strand is synthesized using the undamaged strand as template. Ultraviolet (UV) light is known to induce two primary forms of DNA damage, the cyclobutane pyrimidine dimer and the 6-4 photoproduct, both of which destabilize the DNA double helix. The uvs9 strain of Chlamydomonas reinhardtii was isolated based on its sensitivity to UV light and was subsequently shown to have a defect in NER. In this work, the UVS9 gene was cloned through molecular mapping and shown to encode a homolog of XPG, the structure-specific nuclease responsible for cleaving damaged DNA strands 3' to sites of damage during NER. 3' RACE revealed that the UVS9 transcript is alternatively polyadenylated. The predicted UVS9 protein is nearly twice as long as other XPG homologs, primarily due to an unusually long spacer region. Despite this difference, amino acid sequence alignment of UVS9p with XPG homologs revealed a new conserved domain involved in TFIIH interaction.
核苷酸切除修复（NER）是去除使DNA双螺旋不稳定的DNA损伤的关键途径。在NER过程中，一种蛋白质复合物协同作用，在损伤两侧切割受损的DNA链。产生的含损伤的寡核苷酸从DNA上被置换下来，并以未受损链为模板合成一条替换链。已知紫外线（UV）会诱导两种主要形式的DNA损伤，即环丁烷嘧啶二聚体和6-4光产物，这两种损伤都会使DNA双螺旋不稳定。莱茵衣藻的uvs9菌株是基于其对紫外线的敏感性而分离出来的，随后被证明在NER方面存在缺陷。在这项工作中，通过分子定位克隆了UVS9基因，并证明它编码XPG的一个同源物，XPG是一种结构特异性核酸酶，负责在NER过程中在损伤位点的3'端切割受损的DNA链。3' RACE显示UVS9转录本存在可变聚腺苷酸化。预测的UVS9蛋白几乎是其他XPG同源物的两倍长，主要是由于一个异常长的间隔区。尽管存在这种差异，但UVS9p与XPG同源物的氨基酸序列比对揭示了一个参与TFIIH相互作用的新保守结构域。
