PRE-TRANSCRIPTIONAL CAPPING IN BIOSYNTHESIS OF CYTOPLASMIC POLYHEDROSIS-VIRUS MESSENGER-RNA
PRE-TRANSCRIPTIONAL CAPPING IN BIOSYNTHESIS OF CYTOPLASMIC POLYHEDROSIS-VIRUS MESSENGER-RNA
复制标题
DOI：
10.1073/pnas.75.3.1086
复制
发表时间：
1978-01-01
影响因子：
11.1
通讯作者：
FURUICHI, Y
中科院分区：
文献类型：
--
作者：
FURUICHI, Y
细胞质型多角体病毒的体外合成依赖于甲基供体S-腺苷蛋氨酸(ADO-Met)的存在。竞争性甲基化抑制剂S-腺苷同型半胱氨酸(ADOHcy)也能有效地刺激CPVmRNA的合成，导致含有5‘端GpppA和PPA的病毒mRNA的合成，而不是像ADOMet观察到的m7GpppAm的合成。除ADOHcy外，其他ADOMet类似物，包括S-腺硫氨酸和腺苷，也能刺激CPVmRNA的合成，但程度比ADOHcy或ADOMet小。为了研究帽子形成和mRNA合成之间的关系，在RNA合成反应混合物(包含ADOMet)中，用相应的β，γ-亚胺类似物取代了核苷三磷酸，这些类似物对核苷酸磷酸水解酶(一种参与帽子形成的酶)具有抗性。虽然在UMP-PNHP或GMP-PNHP存在的情况下有mRNA合成，但当AMP-PNHP替代ATP时，没有观察到mRNA的合成。因为成为CPV mRNA5‘-末端核苷酸的ATP分子必须在β-γ处被切割。在帽形成过程中的位置，结果表明，在这个病毒转录系统中，帽的形成是mRNA合成的先决条件，即转录前事件。
The in vitro synthesis of cytoplasmic polyhedrosis virus (CPV) mRNA was previously shown to be dependent upon the presence of the methyl donor S-adenosylmethionine (AdoMet). The competitive inhibitor of methylation, S-adenosylhomocysteine (AdoHcy), also stimulates CPV mRNA synthesis efficiently, resulting in the synthesis of viral mRNA containing 5''-terminal GpppA and ppA, rather than m7GpppAm as observed with AdoMet. Besides AdoHcy, other AdoMet analogs, including S-adenosylethionine and adenosine, also stimulate CPV mRNA synthesis but to a smaller extent than does AdoHcy or AdoMet. To study the relationship between cap formation and mRNA synthesis, nucleoside triphosphates were replaced in the RNA-synthesizing reaction mixture (containing AdoMet) by the corresponding .beta.,.gamma.-imido analogs, which are resistant to nucleotide phosphohydrolase, an enzyme involved in cap formation. Although mRNA synthesis occurred in the presence of UMP-pNHp or GMP-pNHp, none was observed when AMP-pNHp was substituted for ATP. Because the ATP molecule that becomes the 5''-terminal nucleotide of CPV mRNA must be cleaved at the .beta.-.gamma. position during cap formation, the results suggest that, in this viral transcription system, cap formation is a prerequisite to mRNA synthesis, i.e., a pretranscriptional event.