Ven Murthy M R
J Neurochem. 1982 Jan;38(1):28-40. doi: 10.1111/j.1471-4159.1982.tb10850.x.
The presence and identity of 5'-terminal cap structures in rat brain polysomal mRNA were investigated by radiolabeling the mRNA by periodate oxidation and [3H]sodium borohydride reduction or by beta-elimination of 5'-terminal nucleoside and incorporation of 32P in the presence of polynucleotide kinase. The labeled mRNAs were digested with nucleases and the cap structures were isolated and identified by chromatographic and electrophoretic procedures The results showed that rat brain mRNAs contained cap 1 and cap 2 structures and no caps of the zero type. The proportion of cap 2 was higher than that of cap 1. Both caps had 7-methylguanosine (m7G) as the 5'-terminal nucleoside, which was linked to the next nucleoside by an inverted triphosphate bridge, as in other eukaryotic mRNAs. The most prominent nucleoside in the 5'-penultimate position was 6-methyl-2'-O-methyladenosine [m6A(m)] followed by 2'-O-methyladenosine [A(m)], which together contributed to nearly 70% of both cap 1 and cap 2 structures. 2'-O-Methylguanosine [G(m)] accounted for approximately 18%, the rest being made up of 2'-O-methylcytidine [C(m)] and 2'-O-methyluridine [U(m)].
通过高碘酸盐氧化和[3H]硼氢化钠还原对大鼠脑多聚核糖体mRNA进行放射性标记，或通过β-消除5'-末端核苷并在多核苷酸激酶存在下掺入32P，研究了大鼠脑多聚核糖体mRNA中5'-末端帽结构的存在和性质。用核酸酶消化标记的mRNA，通过色谱和电泳方法分离并鉴定帽结构。结果表明，大鼠脑mRNA含有帽1和帽2结构，没有零型帽。帽2的比例高于帽1。两种帽都以7-甲基鸟苷（m7G）作为5'-末端核苷，它通过反向三磷酸桥与下一个核苷相连，这与其他真核mRNA一样。5'-倒数第二个位置最突出的核苷是6-甲基-2'-O-甲基腺苷[m6A(m)]，其次是2'-O-甲基腺苷[A(m)]，它们共同构成了帽1和帽2结构的近70%。2'-O-甲基鸟苷[G(m)]约占18%，其余由2'-O-甲基胞苷[C(m)]和2'-O-甲基尿苷[U(m)]组成。
