HDAC1基因沉默对人胰腺癌细胞PaTu8988细胞周期的影响

目的 探讨组蛋白脱乙酰基酶1( HDAC1)基因沉默对人胰腺癌PaTu8988细胞周期影响及可能机制.方法 常规培养胰腺癌PaTu8988细胞,分为对照组、阴性siRNA转染(c-siRNA)组及15、30 nmol/L HDAC1 siRNA转染组.采用脂质体2000转染细胞48 h后,应用蛋白质印迹法检测细胞HDAC1基因沉默效率及p21基因表达;流式细胞法检测细胞周期的变化.结果 与对照组比较,30 nmol/L HDAC1 siRNA组PaTu8988细胞的HDAC1蛋白表达明显下降,P21蛋白表达明显增加;G2/M 期细胞比例显著减少[(21.48±3.67)％比(28.28±2.94)％,P＜0.05],S期细胞比例显著增加[(50.20±6.85)％比(32.49±2.78)％,P＜0.05].结论 HDACl siRNA能特异、有效地抑制人胰腺癌PaTu8988细胞HDACl的表达,引起细胞S期阻滞,其机制可能与上调p21蛋白表达有关.     

RNA干扰DNA甲基转移酶1对人胰腺癌PaTu8988细胞增殖和凋亡的影响

目的 观察以DNA甲基转移酶1(DNA methy transferas 1,DNMT1)基因为靶基因的RNA干扰对人胰腺癌PaTu8988细胞增殖及凋亡的影响.方法 设计、合成针对DNMT1基因的siRNA和阴性对照siRNA(N-siRNA).实验分为空白对照组、脂质体组(仅予脂质体)、N-siRNA组(转染30 nmol N-siRNA)、siRNA组(转染30 nmol siRNA).siRNA转染48 h后,实时PCR法检测DNMT1 mRNA水平;WST-8法检测细胞增殖;流式细胞技术检测细胞凋亡.结果 siRNA组DNMT1 mRNA的抑制率为(86.0±4.3)%,明显高于N-siRNA组的(40.1±2.2)%和空白对照组的0(P＜0.01);细胞存活率为(47.6±5.6)%,明显低于N-siRNA组的(68.1±4.1)%和空白对照组的100%(P＜0.01);细胞凋亡率为(14.94±2.89)%,明显高于空白对照组的(7.51±1.12)%、脂质体组的(7.06±0.39)%、N-siRNA组的(8.84±1.44)%(均P＜0.01).结论 siRNA能特异、有效地抑制人胰腺癌PaTu8988细胞DNMT1mRNA的表达,同时抑制细胞增殖、促进细胞凋亡.     

组蛋白去乙酰化酶1对人胰腺癌细胞增殖凋亡的影响

目的 观察沉默组蛋白去乙酰化酶1(HDAC1)基因对人胰腺癌PaTu8988细胞增殖及凋亡的影响.方法 培养胰腺癌PaTu8988细胞株,设空白对照组(未予任何处理)、阴性对照组[予30 nmol/L阴性小干扰RNA(siRNA)]、HDACI低剂量组(予15 nmol/L HDAC1 siRNA)和HDAC1高剂量组(予30 nmol/L HDAC1 siRNA),siRNA转染48 h后,分别采用相对实时定量PCR法和Western印迹法检测HDAC1基因在mRNA和蛋白水平的沉默效率,细胞计数试剂盒法检测siRNA干扰前、后细胞增殖变化,流式细胞技术检测干扰前、后细胞凋亡变化.结果 转染HDAC1siRNA 48 h后,低剂量组和高剂量组人胰腺癌PaTu8988细胞中HDAC1 mRNA表达率分别为46.1%±6.1%和32.3%±1.4%,均显著低于空白对照组(100.0%±3.4%)和阴性对照组(87.4%±28.3%),差异有统计学意义(P值均<0.05).空白对照组和阴性对照组HDAC1蛋白表达水平高于其余两组.空白对照组、阴性对照组、HDAC1低剂量组和HDAC1高低剂量组的细胞存活率分别为100.0%±17.1%、87.1%±5.0%、68.7%±4.7%和61.6%±2.0%,细胞凋亡率分别为4.20%±0.95%、4.59%±1.26%、10.09%±1.36%和11.19%±6.07%,空白对照组和阴性对照组与其余两组比较,差异均有统计学意义(P值均<0.05).结论 HDAC1 siRNA能特异、有效地抑制人胰腺癌PaTu8988细胞HDAC1表达,抑制细胞增殖、诱导细胞凋亡.     

胰腺癌细胞株原钙黏附蛋白8基因的甲基化状态

目的 分析原钙黏附蛋白8(protocadherin 8,PCDH8)基因在胰腺癌细胞株的甲基化状态.方法 抽提6株胰腺癌细胞株PANC1、ASPC1、BxPC3、CFPAC、PaTu8988、SW1990和2例正常胰腺组织的总RNA,以甲基化特异性PCR(MSP)法检测PCDH8甲基化情况.应用DNA甲基化转移酶(DNMT)抑制剂5-氮杂2'-脱氧胞苷(5-Aza-dC)处理6株胰腺癌细胞株,采用实时定量PCR法检测处理前后细胞的PCDH8 mRNA表达.结果 2例正常胰腺组织PCDH8基因未发生甲基化,PANC1、BxPC3、CFPAC胰腺癌细胞株PCDH8基因部分甲基化,而PaTu8988、ASPC1、SW1990细胞完全甲基化.PCDH8mRNA在PANC1、SW1990、PaTu8988胰腺癌细胞株中有表达,表达的相对值(RQ)分别为1.576±0.648、0.013±0.008、0.002±0.001;BxPC3、CFPAC、ASPC1细胞株无PCDH8 mRNA表达.5-Aza-dC处理后,胰腺癌细胞株PANC1、ASPC1、BxPC3、CFPAC、PaTu8988、SW1990均有PCDH8 mRNA表达,表达量较处理前明显升高,相对表达量分别为7.463±2.628、10.696±1.539、7.852±2.762、421.815±1.493、118.595±4.089、6.690±1.884.结论 PCDH8基因启动子高甲基化是导致该基因在胰腺癌细胞株表达下降的主要原因之一.     

IRX1在胰腺癌中的表达及其启动子区甲基化状态

目的 检测胰腺癌的易洛魁族同源盒基因(IRX1)的表达及其启动子区的甲基化状态,探讨两者间的相关性.方法 采用实时PCR法检测12例胰腺癌组织及6株胰腺癌细胞株的IRX1 mRNA 表达.基因序列分析IRX1基因启动子区结构.应用甲基化抑制剂5-氮杂-2＇-脱氧胞苷(5-Aza-dC)处理胰腺癌细胞,采用甲基化特异性PCR(MSP)、非甲基化特异性PCR (USP)及实时PCR检测处理前后IRX1启动子甲基化状态和IRX1 mRNA表达.结果 胰腺癌组织IRX1 mRNA的表达量为0.31±0.11,显著低于癌旁正常胰腺组织的1.05±0.32(P ＜0.01).胰腺癌细胞AsPCl、BxPC3、Capan-2、PANC1、PaTu8988和SW1990的IRX1 mRNA表达量分别为0.36±0.08、0.34±0.16、0.37±0.11、0.25±0.06、0.31±0.04、0.36±0.02,均显著低于人肾上皮293细胞的1.03±0.28(P＜0.05或＜0.01).IRX1基因启动子区富含CpG岛.各胰腺癌细胞株IRX1基因启动子CpG岛对应位点均有甲基化,经5-Aza-dC处理后甲基化状态得以逆转,IRX mRNA的表达也得以恢复.结论 胰腺癌的IRX1 mRNA表达下降,与其IRX1基因启动子区CpG岛高甲基化状态相关.     

RNA干扰DNMT1基因对胰腺癌细胞BxPC-3增殖的影响及相关机制

目的:探讨RNA干扰DNMT1基因对胰腺癌细胞BxPC-3增殖的影响及相关机制.方法:利用Lipofectamine TM2000转染DNMT1-siRNA至胰腺癌细胞BxPC-3.实验共分为3组:实验组(转染DNMT1-siRNA)、阴性对照组(转染negative-siRNA)和空白对照组(转染脂质体).转染48h后,应用荧光定量PCR法和Western blot法分别检测细胞中DNMT1 mRNA和蛋白的表达水平;MTT法检测细胞体外增殖活力;FCM法检测细胞凋亡;甲基化特异性PCR法(MSP)检测抑癌基因p16、RASSF1A和ppENK的启动子甲基化状态.结果:与空白对照组和阴性对照组相比,实验组的DNMT1 mRNA及蛋白表达量均显著降低(P<0.01);实验组细胞增殖明显受到抑制(P<0.05),细胞凋亡率明显增加(44.46%±5.98%vs3.74%±1.02%vs5.07%±1.16%,P<0.01).空白对照组与阴性对照组的p16、RASSF1A和ppENK基因甲基化阳性,而实验组的p16和ppENK基因甲基化阴性,RASSF1A基因部分甲基化.结论:DNMT1基因表达下调后,能抑制胰腺...     

人胰腺癌细胞株MUC2基因启动子区甲基化状态检测和分析

近年表观遗传学修饰方式之-的DNA甲基化成为肿瘤研究的热点。目前已发现胰腺癌中存在MUC2表达异常。目的：探讨人胰腺癌细胞株MUC2表达与其基因启动子区甲基化的关系，以了解胰腺癌的发生机制。方法：以人胰腺癌细胞株AsPC-1、BxPC-3、CFPAC-1、PANC-1、SW1990和PaTu8988s为研究对象，以逆转录聚合酶链反应（RT-PCR）和免疫细胞化学方法检测去甲基化制剂DNA甲基转移酶抑制剂5-氮杂-2’-脱氧胞苷（5-Aza-CdR）处理前后各胰腺癌细胞株MUC2 mRNA／蛋白表达的变化，以甲基化特异性PCR（MSP）结合测序检测MUC2基因启动子区CpG岛甲基化状态。结果：5-Aza-CdR处理前．胰腺癌细胞株AsPC．1、CFPAC-1和SW1990无MUC2mRNA／蛋白表达或低表达：经5-Aza-CdR处理后，MUC2mRNA／蛋白重新表达。MSP结合测序显示上述胰腺癌细胞株MUC2基因启动子区CpG岛存在高甲基化。结论：人胰腺癌细胞株MUC2表达抑制与其基因启动子区CpG岛高甲基化相关。MUC2基因启动子区CpG岛高甲基化可能在胰腺癌的发生、发展中起-定作用。     

MUC2基因甲基化在胰腺癌细胞株、胰腺癌患者外周血中的检测及意义

目的 检测MUC2基因在胰腺癌细胞株、胰腺癌患者外周血中的甲基化情况,探讨MUC2基因甲基化对胰腺癌早期诊断的价值.方法 收集长海医院消化内科实验室保存的人胰腺癌细胞系SW1990、ASPC、PANC1、BxPC3、PaTu8988、CFPAC1及40例胰腺癌、15例慢性胰腺炎患者和25例正常对照者外周血标本,应用甲基化敏感性限制性内切酶(methylation-sensitive restriction endonuelease,MS-RE)为基础的PCR法检测MUC2基因甲基化.结果 人胰腺癌细胞系PANC1、BxPC3、PaTu8988未发生MUC2基因甲基化;ASPC、CFPAC1、SW1990胰腺癌细胞系发生MUC2基因甲基化.外周血标本中,40例胰腺癌标本甲基化率为40.0%(16例),15例慢性胰腺炎无甲基化,25例正常对照甲基化率4.0%(1例).胰腺癌与慢性胰腺炎、正常对照之间的甲基化率有显著差异(P＜0.01).外周血标本MUC2基因启动子CpG岛甲基化检测诊断胰腺癌的敏感性为40%、特异性为97.5%、诊断准确性68.8%、阳性预测值94.1%、阴性预测值61.9%.结论 用甲基化限制性酶切PCR法对外周血进行MUC2基因启动子区高甲基化检测可望成为新的胰腺癌诊断的重要实验室辅助手段.     

胰腺癌细胞株中Elastase 3B基因启动子异常甲基化研究

目的 探讨Elastase 3B(ELA3B)基因在胰腺癌中低表达的分子机制.方法 应用RT-PCR方法检测2例正常胰腺组织和BxPC、CFPAC、PaTu8988、PANC1、SW1990 5株胰腺癌细胞株ELA3B基因表达.利用去甲基化试剂5-氮-2'-脱氧胞嘧啶(DAC)处理细胞株,再检测ELA3B基因表达,并用甲基化特异性PCR检测和测序进行验证.结果 ELA3B在正常胰腺组织中表达,而在BxPC、CFPAC、PaTu8988、PANC1和SW1990 5株胰腺癌细胞株中均无表达.DAC处理后,BxPC、PaTu8988、PANC1和SW1990 4株胰腺癌细胞株表达ELA3B,而CFPAC仍不表达.正常胰腺组织和PANC1 ELA3B基因部分甲基化,而其他4株胰腺癌细胞株则高甲基化.结论 ELA3B基因启动子的高甲基化是导致该基因在胰腺癌中表达下降的主要原因之一.     

靶向B7-H3基因RNA干扰慢病毒的构建及人胰腺癌PaTu8988稳定感染细胞株的建立

目的 构建靶向人B7同源性3(B7-H3)基因的小发夹RNA(shRNA)的慢病毒载体,并建立稳定感染的胰腺癌PaTu8988细胞株.方法 根据GenBank提供的B7-H3 cDNA序列,设计4条靶向B7-H3的siRNA序列,构建重组干扰质粒pGCSIL-GFP-B7-H3-shRNA.将重组干扰质粒和过表达B7-H3质粒共同转染293T细胞,经蛋白质印迹法筛选出干扰效果最佳的重组干扰质粒.该质粒经慢病毒包装,并感染胰腺癌PaTu8988细胞株,建立稳定低表达B7-H3细胞株.应用实时定量PCR及蛋白质印迹法检测细胞B7-H3基因的表达抑制率.结果 携带干扰效果最好的shRNA的慢病毒感染PaTu8988细胞,建立了稳定低表达B7-H3基因的PaTu8988细胞株,其B7-H3 mRNA表达的抑制率达96.8％,B7-H3蛋白表达的抑制率达88.1％.结论 成功构建了人B7-H3-RNAi的慢病毒载体,并建立了稳定感染的低表达B7-H3基因的PaTu8988细胞株.     

嗜肺军团菌血清I型菌株随机扩增多态性DNA指纹图谱研究

目的采用随机扩增多态性DNA(RAPD)方法研究我国58株嗜肺军团菌血清1型(Lp1)菌株的基因型特征。方法58株嗜肺军团菌血清1型菌株来自北京和深圳市的集中空调冷却塔水和温泉水,随机引物采用5’-CGGCGGCG-GCGG-3’序列,分析Lp1型军团菌RAPD基因型和温度、pH值的关系。结果58株Lp1型菌株共分为17个RAPD基因型。与集中空调冷却塔水Lp1型菌株相比,温泉水分离的菌株基因型具有较高的多态性。深圳市29株集中空调冷却塔水分离的Lp1菌株,共呈现出3个RAPD基因型,北京市24株来自温泉水的Lp1菌株分为12个RAPD型,5株来自集中空调冷却塔水的Lp1型菌株分为两个RAPD型。温泉水Lp1菌株的基因型差异和水温度和pH值无明显的关联。结论RAPD分型方法可用于我国Lp1菌株的基因分型,不同地区和来源的Lp1型军团菌菌株具有特征性的RAPD基因型,温泉水中分离的Lp1菌株较集中空调冷却塔水分离菌株基因型呈现较高的基因多态性。     

Functional redundancy between the XLF and DNA-PKcs DNA repair factors in V(D)J recombination and nonhomologous DNA end joining

Classical nonhomologous end joining (C-NHEJ) is a major mammalian DNA double-strand break (DSB) repair pathway that is required for assembly of antigen receptor variable region gene segments by V(D)J recombination. Recombination activating gene endonuclease initiates V(D)J recombination by generating DSBs between two V(D)J coding gene segments and flanking recombination signal sequences (RS), with the two coding ends and two RS ends joined by C-NHEJ to form coding joins and signal joins, respectively. During C-NHEJ, recombination activating gene factor generates two coding ends as covalently sealed hairpins and RS ends as blunt 5′-phosphorylated DSBs. Opening and processing of coding end hairpins before joining by C-NHEJ requires the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). However, C-NHEJ of RS ends, which do not require processing, occurs relatively normally in the absence of DNA-PKcs. The XRCC4-like factor (XLF) is a C-NHEJ component that is not required for C-NHEJ of chromosomal signal joins or coding joins because of functional redundancy with ataxia telangiectasia mutated kinase, a protein that also has some functional overlap with DNA-PKcs in this process. Here, we show that XLF has dramatic functional redundancy with DNA-PKcs in the V(D)J SJ joining process, which is nearly abrogated in their combined absence. Moreover, we show that XLF functionally overlaps with DNA-PKcs in normal mouse development, promotion of genomic stability in mouse fibroblasts, and in IgH class switch recombination in mature B cells. Our findings suggest that DNA-PKcs has fundamental roles in C-NHEJ processes beyond end processing that have been masked by functional overlaps with XLF.     

DNA甲基转移酶1在胰腺癌组织中的表达及其临床意义

目的 探讨DNA甲基转移酶1(DNMT1)在胰腺癌组织中的表达及其临床意义.方法 收集手术切除的30例胰腺癌组织和配对癌旁组织.采用实时定量PCR法检测DNMT1 mRNA的表达;免疫组织化学法检测DNMT1蛋白的表达;分析胰腺癌组织DNMT1蛋白表达强度与临床病理参数之间的关系.结果 胰腺癌组织中DNMT1 mRNA的表达量为2.32(1.17～5.17),显著高于配对癌旁组织的0.78(0.07～3.14,P＜0.05).胰腺癌组织中导管细胞DNMT1蛋白表达阳性率为(54.5±21.2)%,显著高于癌旁组织(10.9±15.0)%的表达阳性率(P＜0.01).以胰腺癌导管细胞DNMT1阳性率54.5%为界,分为高表达组(19例)和低表达组(11例).DNMT1表达强度和临床分期(x2=6.897,P=0.029)、淋巴结转移(x2=4.739,P=0.029)、神经浸润与否(x2=5.44,P=0.020)相关,而与年龄、性别、肿瘤位置、肿瘤大小、肿瘤分化、血清CEA和CA19-9浓度无关.结论 胰腺癌组织DNMT1 mRNA和蛋白表达明显增加,DNMT1蛋白表达强度与胰腺癌的侵袭力、淋巴结转移和神经浸润相关.     

Rotational dynamics of DNA on the nucleosome surface markedly impact accessibility to a DNA repair enzyme

Histones play a crucial role in the organization of DNA in the nucleus, but their presence can prevent interactions with DNA binding proteins responsible for repair of DNA damage. Uracil is an abundant mutagenic lesion recognized by uracil DNA glycosylase (UDG) in the first step of base excision repair (BER). In nucleosome core particles (NCPs), we find substantial differences in UDG-directed cleavage at uracils rotationally positioned toward (U-In) or away from (U-Out) the histone core, or midway between these orientations (U-Mid). Whereas U-Out NCPs show a cleavage rate just below that of naked DNA, U-In and U-Mid NCPs have markedly slower rates of cleavage. Crosslinking of U-In DNA to histones in NCPs yields a greater reduction in cleavage rate but, surprisingly, yields a higher rate of cleavage in U-Out NCPs compared with uncrosslinked NCPs. Moreover, the next enzyme in BER, APE1, stimulates the activity of human UDG in U-Out NCPs, suggesting these enzymes interact on the surface of histones in orientations accessible to UDG. These data indicate that the activity of UDG likely requires “trapping” transiently exposed states arising from the rotational dynamics of DNA on histones.     

DNA修复酶hMTH1在乙型肝炎病毒x基因致人肝细胞系L02细胞恶性转化中的意义

目的 通过转摹因细胞模型L02/HBx观察乙型肝炎病毒x基因(HBx)对DNA修复酶hMTH1转录表达的调控及其对人肝细胞系L02细胞生物学特性的影响.方法 传代培养稳定表达HBx的转基因细胞模型ID2/HBx及空白对照组ID2细胞和空载体对照组L02/pcDNA3.1细胞,倒置显微镜下观察各组细胞的形态学特征,以四甲基偶氮唑盐(MTT)比色法、流式细胞术枪测各组细胞增殖、细胞周期和凋亡状况,并进行软琼脂克隆形成实验观察细胞的恶性转化能力.同时应用实时定量PCR测定各组细胞DNA修复酶hMTH1的表达水平.结果 镜下观察发现L02/HBx细胞与对照组ID2细胞相比形态发生明显改变.MTT法显示L02/HBx细胞生长速度比两对照组显著加快.流式细胞术结果表明,HBx可加速细胞周期进程、抑制细胞凋亡.软琼脂克隆形成实验发现L02/HBx细胞的克隆形成率明显高于L02细胞和ID2/pcDNA3.1细胞(P<0.05).实时定量PCR检测发现hMTH1在L02/HBx细胞中的表达显著高于L02细胞和L02/pcDNA3.1细胞(P<0.05).结论 HBx可诱导L02细胞发生恶性转化,在此过程中DNA修复酶hMTH1可出现反应性的上调表达.     

HIV-1型前病毒基因检测芯片的研制及应用

目的研制艾滋病病毒1型(HIV-1)前病毒基因检测芯片，并将其应用到临床样本的检测中。方法合成多对引物，经筛选实验后选出6对适宜的引物用于逆转录-聚合酶链反应(RT—PCR)，扩增HIV基因组gag区(保守区)6个HIV目的基因片段，扩增小鼠GAPDH基因片段作为阳性内参片段，PCR扩增辣椒红素基因片段作为阴性对照片段。将上述片段克隆到pMD18-T载体上，从中选取3个HIV-1目的片段、阳性对照片段和阴性对照片段进行PCR扩增，扩增产物经纯化后点在尼龙膜上，制备成核酸检测芯片。地高辛PCR标记样本核酸与芯片杂交后，用酶联显色，分析结果。结果共检测了98份阳性样本和30个阴性样本，敏感性达93．9％，特异性为100．0％。结论该HIV-1前病毒基因检测芯片成本较低，具有较高的特异性和灵敏度，可以用于HIV-1感染和母婴传播的早期诊断。     

Modulation of the cGAS-STING DNA sensing pathway by gammaherpesviruses

Infection of cells with DNA viruses triggers innate immune responses mediated by DNA sensors. cGMP-AMP synthase (cGAS) is a key DNA sensor that produces the cyclic dinucleotide cGMP-AMP (cGAMP) upon activation, which binds to and activates stimulator of interferon genes (STING), leading to IFN production and an antiviral response. Kaposi’s sarcoma-associated herpesvirus (KSHV) is a DNA virus that is linked to several human malignancies. We report that KSHV infection activates the cGAS-STING pathway, and that cGAS and STING also play an important role in regulating KSHV reactivation from latency. We screened KSHV proteins for their ability to inhibit this pathway and identified six viral proteins that block IFN-β activation through this pathway. This study is the first report identifying multiple viral proteins encoded by a human DNA virus that inhibit the cGAS-STING DNA sensing pathway. One such protein, viral interferon regulatory factor 1 (vIRF1), targets STING by preventing it from interacting with TANK binding kinase 1 (TBK1), thereby inhibiting STING’s phosphorylation and concomitant activation, resulting in an inhibition of the DNA sensing pathway. Our data provide a unique mechanism for the negative regulation of STING-mediated DNA sensing. Moreover, the depletion of vIRF1 in the context of KSHV infection prevented efficient viral reactivation and replication, and increased the host IFN response to KSHV. The vIRF1-expressing cells also inhibited IFN-β production following infection with DNA pathogens. Collectively, our results demonstrate that gammaherpesviruses encode inhibitors that block cGAS-STING–mediated antiviral immunity, and that modulation of this pathway is important for viral transmission and the lifelong persistence of herpesviruses in the human population.Kaposi’s sarcoma-associated herpesvirus (KSHV/HHV8) is the etiological agent of several human malignancies, including Kaposi’s sarcoma (KS), multicentric Castleman’s disease, and primary effusion lymphoma (1, 2). Evasion of the host innate immune response is essential for viral infection, replication, latency, transmission, and lifelong persistence.A member of the gammaherpesvirus subfamily, KSHV contains a large dsDNA genome that encodes for more than 80 ORFs. Different pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), nucleotide-binding domain leucine-rich repeat-containing (NLR) proteins, and retinoic acid-inducible gene-I–like receptors (RLRs), are activated upon KSHV infection in different cell types (3–5). As is the case with many pathogens, multiple PRRs can detect an incoming pathogen in the cell. Depending on the cell type, detection of viral DNA may take place in the nucleus (6) or in the cytoplasm due to premature release of the herpesviral DNA into the cytoplasm (7). It is plausible that defective herpesvirus virions release their genomic contents into the cytoplasm rather than the nucleus and that this viral DNA triggers cytosolic DNA sensors to be activated. Additionally, HSV-1 infection induces mitochondrial stress, which results in the release of mtDNA into the cytoplasm, thereby activating the cGMP-AMP synthase (cGAS) and stimulator of interferon-dependent genes (STING) DNA sensing pathway (8).cGAS and STING are important mediators of the innate immune response to DNA viruses. Activation of this pathway leads to the production of type I interferon (IFN) and a subsequent antiviral response. STING was identified as a critical regulator of the DNA sensing pathway (9, 10) that activates type I IFN signaling by binding foreign DNA directly (11) or through the action of sensors, such as cGAS (12–15). Upon detecting DNA from DNA viruses, including HSV-1 (12, 13), cGAS synthesizes cGMP-AMP (cGAMP), a moiety that binds to and activates STING to induce IFN (12, 13). As is the case with other pathogens, including HSV-1, it is highly plausible that multiple DNA sensing pathways can detect KSHV. It is currently not known whether the DNA sensing pathway mediated through cGAS and STING is also activated upon KSHV infection and whether viral proteins expressed by KSHV inhibit this pathway.     

Yeast Rev1 protein promotes complex formation of DNA polymerase ζ with Pol32 subunit of DNA polymerase δ

Yeast DNA polymerase (Pol) δ, essential for DNA replication, is comprised of 3 subunits, Pol3, Pol31, and Pol32. Of these, the catalytic subunit Pol3 and the second subunit Pol31 are essential, whereas the Pol32 subunit is not essential for DNA replication. Although Pol32 is an integral component of Polδ, it is also required for translesion synthesis (TLS) by Polζ. To begin to decipher the bases of Pol32 involvement in Polζ-mediated TLS, here we examine whether Pol32 physically interacts with Polζ or its associated proteins and provide evidence for the physical interaction of Pol32 with Rev1. Rev1 plays an indispensable structural role in Polζ-mediated TLS and it binds the Rev3 catalytic subunit of Polζ. Here, we show that although Pol32 does not directly bind Polζ, Pol32 can bind the Rev1–Polζ complex through its interaction with Rev1. We find that Pol32 binding has no stimulatory effect on DNA synthesis either by Rev1 in the Rev1–Pol32 complex or by Polζ in the Polζ–Rev1–Pol32 complex, irrespective of whether proliferating cell nuclear antigen has been loaded onto DNA or not. We discuss evidence for the biological significance of Rev1 binding to Pol32 for Polζ function in TLS and suggest a structural role for Rev1 in modulating the binding of Polζ with Pol32 in Polδ stalled at a lesion site.