真核 mRNA 通过 7-甲基鸟苷帽进行共转录 5' 端修饰。在高等真核生物中,帽子带有额外的甲基化,例如m6 A m — mRNA 5' 端特有的常见表观转录组标记。这种修饰受到 PCif1 甲基转移酶和 FTO 去甲基化酶的调节,但其生物学功能仍不清楚。在这里,我们设计并合成了m6 A m -cap–m 7 Gppp Bn6 A m pG 的三核苷酸 FTO 抗性N 6-苄基类似物(称为AvantCap ),并使用 T7 聚合酶将其整合到 mRNA 中。与典型的加帽转录本相比,携带Bn6 A m的 mRNA 显示出多种优势。 Bn6 A m部分被证明可作为反相高效液相色谱 (RP-HPLC) 纯化手柄,允许分离加帽和未加帽的 RNA 种类,并产生比参考帽具有更低 dsRNA 含量的转录本。在一些培养的细胞中, Bn6 A m mRNA 比携带 A m或m6 A m 的mRNA 提供更高
Structural requirements for Caenorhabditis elegans DcpS substrates based on fluorescence and HPLC enzyme kinetic studies
摘要:
The activity of the Caenorhabditis elegans scavenger decapping enzyme (DcpS) on its natural substrates and dinucleotide cap analogs, modified with regard to the nucleoside base or ribose moiety, has been examined. All tested dinucleotides were specifically cleaved between β‐ and γ‐phosphate groups in the triphosphate chain. The kinetic parameters of enzymatic hydrolysis (Km, Vmax) were determined using fluorescence and HPLC methods, as complementary approaches for the kinetic studies of C. elegans DcpS. From the kinetic data, we determined which parts of the cap structure are crucial for DcpS binding and hydrolysis. We showed that m32,2,7GpppG and m32,2,7GpppA are cleaved with higher rates than their monomethylated counterparts. However, the higher specificity of C. elegans DcpS for monomethylguanosine caps is illustrated by the lower Km values. Modifications of the first transcribed nucleotide did not affect the activity, regardless of the type of purine base. Our findings suggest C.elegans DcpS flexibility in the first transcribed nucleoside‐binding pocket. Moreover, although C. elegans DcpS accommodates bulkier groups in the N7 position (ethyl or benzyl) of the cap, both 2′‐O‐ and 3′‐O‐methylations of 7‐methylguanosine result in a reduction in hydrolysis by two orders of magnitude.