Molecular Biology of the Ribonuclease A Gene Superfamily

我们实验室正在进行的项目主要集中在促进宿主防御的核糖核酸酶(嗜酸性粒细胞核糖核酸酶，RNase7和RNase8，以及白细胞RNaseA-2)，努力了解它们的生物学、进化和抗菌作用的机制(Moser，Chan等，正在准备中)。 在本报告所述期间，我们公布了赵伟博士在北京联合学院中国休学期间发起的一项研究的结果，该研究在暑期实习生Steven Siegel的大量努力下继续并完成。为了加深我们对哺乳动物核糖核酸酶序列的了解，我们从四种松鼠(啮齿目，松鼠科)中克隆了新的RNase1基因。松鼠RNase1基因编码典型的RNaseA核糖核酸酶，每个核糖核酸酶含有8个半胱氨酸、一个保守的CKXXNTF特征基序和一个典型的His(12)-Lys(41)-His(119)催化三联体。有两个等位基因编码先锋松鼠RNase1，其中包括一个Ser(18)&lt；--&gt；Pro，类似于在Rattus exulans基因组中发现的RNase1重复序列的序列多态性。有趣的是，尽管松鼠RNase1基因彼此之间关系密切(氨基酸序列同源性为77%-95%)，但作为一个整体，该簇与包括其他啮齿动物RNase1基因的簇是不同的。我们检查了Sciuridae RNase1S与Muridae/Cricetdae RNase1S的特定位置，并确定分歧位置位于外表面，完全保留了催化缝隙。

Ongoing projects in our laboratory focus primarily on RNase A ribonucleases that promote host defense (the eosinophil ribonucleases, RNases 7 and 8, and leukocyte RNase A-2) with efforts directed toward understanding their biology, evolution and mechanism of antimicrobial action (Moser, Chan et al., in preparation). During this reporting period, we published the results of a study initiated by Dr. Wei Zhao during his sabbatical from Beijing Union College, Beijing, China, that was continued and completed as a result of the substantial efforts of a summer intern, Steven Siegel. In an effort to augment our current understanding of divergent mammalian RNase A ribonuclease sequences, we identified novel RNase 1 genes from four species of squirrel (order Rodentia, family Sciuridae). Squirrel RNase 1 genes encode typical RNase A ribonucleases, each with eight cysteines, a conserved CKXXNTF signature motif, and a canonical His(12)-Lys(41)-His(119) catalytic triad. Two alleles encode Callosciurus prevostii RNase 1, which include a Ser(18)<-->Pro, analogous to the sequence polymorphisms found among the RNase 1 duplications in the genome of Rattus exulans. Interestingly, although the squirrel RNase 1 genes are closely related to one another (77-95% amino acid sequence identity), the cluster as a whole is distinct and divergent from the clusters including RNase 1 genes from other rodent species. We examined the specific sites at which Sciuridae RNase 1s diverge from Muridae/Cricetidae RNase 1s and determined that the divergent sites are located on the external surface, with complete sparing of the catalytic crevice.