花园里面“种”鳗鱼

<正>"种"自己的小鳗鱼小丑鱼尼莫正在海葵丛里打着盹,突然听见旁边的沙地上传出细微的声响。到底是谁在制造噪声呢?尼莫透过海葵触须的夹缝,瞥见了一条行为鬼祟的彩色小鳗鱼。这条小鳗鱼专注地"玩"着海底沙——只见它将全身肌肉拉紧,这样原先还十分柔软的身体便变成一根"棍",然后它将自己尖尖的尾部深深地插入沙底。一旦钻到足够深的地方,它便摇摆背鳍,将洞中的沙子推出,看起来就像在打洞。     

Recurring features of local tertiary structural elements in RNA molecules exemplified by hepatitis D virus RNA

Elements of local tertiary structure in RNA molecules are important in understanding structure-function relationships. The loop E motif, first identified in several eukaryotic RNAs at functional sites which share an exceptional propensity for UV crosslinking between specific bases, was subsequently shown to have a characteristic tertiary structure. Common sequences and secondary structures have allowed other examples of the E-loop motif to be recognized in a number of RNAs at sites of protein binding or other biological function. We would like to know if more elements of local tertiary structure, in addition to the E-loop, can be identified by such common features. The highly structured circular RNA genome of the hepatitis D virus (HDV) provides an ideal test molecule because it has extensive internal structure, a UV-crosslinkable tertiary element, and specific sites for functional interactions with proteins including host PKR. We have now found a UV-crosslinkable element of local tertiary structure in antigenomic HDV RNA which, although differing from the E-loop, has a very similar pattern of sequence and secondary structure to the UV-crosslinkable element found in the genomic strand. Despite the fact that the two structures map close to one another, the sequences comprising them are not the templates for each other. Instead, the template regions for each element are additional sites for potential higher order structure on their respective complementary strands. This wealth of recurring sequences interspersed with base-paired stems provides a context to examine other RNA species for such features and their correlations with biological function.