Base-Specific Endo-Exonucleolytic Activity of Chlamydomonas Nuclease C1&2

The reaction kinetics of nuclease C1&2 from Chlamydomonasreinhardtii were studied. It showed endo-exonucleolytic activitywith sugar non-specificity. The relative rates of RNA breakdownwere in order of poly(U) > poly(A) > yeast sRNA. In contrast,poly(G) and poly(C) released almost no acid-soluble materialsafter reacting with nuclease C1&2. The major products ofa 100% limit digest of synthetic RNA homopolymers were mononucleotideswith 3'-phosphate termini. Large oligonucleotides produced duringendo-exonucleolytic degradation also appeared carrying 3'-phosphatetermini. Nuclease C1&2 hydrolyzed single stranded DNA 20times faster than double stranded DNA by endo-exonucleolyticaction, releasing acid-soluble materials. High performance liquidchromatography of a 100% limit digest of salmon testes DNA demonstratedthat the major products were deoxymononucleotides with phosphateat 3'-position. Furthermore, the level of 3'-dCMP among themwas found to be extremely low. Poly(dC) and poly(me⁵dC) werehydrolyzed much more slowly than single stranded (or denatured)DNA, releasing acid-soluble materials. The present results suggestthat nuclease C1&2 is a base-specific nucleate 3'-oligonucleotidohydrolasedifferent from the restriction enzymes. (Received January 13, 1986; Accepted March 25, 1986)     

Tssk1和Tssk2的克隆、表达及其在成熟精子中的分布与亚细胞定位

睾丸特异性丝氨酸/苏氨酸蛋白激酶(Testis-SpecificSerine/Threonine Kinases,TSSKs)可能在精子发生和(或)精子功能调节中起着重要作用,该文研究克隆并表达了小鼠Tssk1和Tssk2基因,纯化得到了Tssk1和Tssk2蛋白激酶,经Western blotting分析,Tssk1和Tssk2皆存在于小鼠和人的成熟精子中。免疫组化的结果显示,Tssk1分布于小鼠的头部(顶体)及整个尾部,Tssk2主要分布在小鼠精子头部顶体后的区域;获能前后的小鼠精子其Tssk1及Tssk2分布模式未发生改变,小鼠Tssk2在诱发顶体反应前后精子中的分布模式也无变化。然而,原来存在于顶体的Tssk1在诱发顶体反应后由于顶体的丢失而未能检出其信号,但尾部的信号不受影响。在人精子中,Tssk1分布区域为颈部及尾部,Tssk2则分布于赤道板的位置。研究结果提示,Tssk1和Tssk2可能对精子功能具有重要调节作用。     

Survivin和COX-2的表达及与胰腺癌预后的关系

目的:评价Survivin和COX-2在胰腺癌中的表达与预后的关系.方法:采用免疫组化二步法检测63例手术切除的原发性胰腺癌组织及11例癌旁非肿瘤胰腺组织中Survivin和COX-2的表达情况.应用spearman相关分析Survivin与COX-2表达的相关性.用Kaplan-Meier法分析生存曲线,多变量Cox比例风险回归模型筛选影响患者生存的独立预后因素.结果:Survivin、COX-2蛋白在胰腺腺癌中的表达呈正相关(r=0.613,P=0.000).Survivin阻性表达患者中位生存时间(9个月)明显小于阴性表达者中位生存时间(21个月),P=0.000; COX-2阳性表达患者中位生存时间(10个月)也明显小于阴性表达者生存时间(大于36个月),P=0.000; Survivin阴性/COX-2阴性组患者(9例)中位生存时间(大于36个月)及1年累计生存率为88.9％,均明显高于单一阳性表达或均阳性表达组.多因素分析(Cox模型)显示分化程度(P=0.002)、临床分期(P=0.000)及Survivin过表达(P=0.005)为影响胰腺癌预后的独立因素.结论:Survivin、COX-2蛋白在胰腺癌组织中表达上调且呈正相关,二者在胰腺癌的发生发展中可能具有协同作用,有望作为靶点用于胰腺癌的靶向治疗.患者的分化程度、临床分期及Survivin的表达水平是胰腺癌患者手术后生存的独立危险因素.