Schnitzler P, Sonntag K C, Müller M, Janssen W, Bugert J J, Koonin E V, Darai G
Institut für Medizinische Virologie, Universität Heidelberg, Germany.
J Gen Virol. 1994 Jul;75 ( Pt 7):1557-67. doi: 10.1099/0022-1317-75-7-1557.
Cytoplasmic DNA viruses encode a DNA-dependent RNA polymerase (DdRP) that is essential for transcription of viral genes. The amino acid sequences of known large subunits of DdRPs contain highly conserved regions. Oligonucleotide primers, deduced from two conserved domains [RQP(T/S)LH and NADFDGDE] were used in PCR experiments for the detection of the corresponding gene of the genome of insect iridescent virus type 6, also known as Chilo iridescent virus (CIV). A specific DNA product of about 150 bp could be amplified and was used as a hybridization probe against the CIV gene library to identify the corresponding gene. The gene encoding the DdRP was identified within the EcoRI fragments M (7099 bp) and L (7400 bp) of CIV DNA, between map units 0.310 and 0.347 (7990 bp). The DNA nucleotide sequence (3153 bp) of the gene encoding the largest subunit of DdRP (RPO1) was determined. Northern blot hybridization revealed the presence of a 3.4 kb RNA transcript in CIV-infected cells that hybridized to the CIV DdRP gene. This predicted viral protein consists of 1051 amino acid residues (120K) and showed considerably higher similarity to the largest subunit of eukaryotic RNA polymerase II than to the homologous proteins of vaccinia virus and African swine fever virus. Phylogenetic analysis suggested that the putative RPO1 of CIV could have evolved from RNA polymerase II after the divergence of the three types of eukaryotic RNA polymerases. The putative RPO1 of CIV lacked the C-terminal domain that is conserved in eukaryotic, eubacterial and other viral RNA polymerases and in this respect was analogous to the RNA polymerases of Archaea. It is hypothesized that the equivalent of the C-terminal domain may reside in another subunit of CIV DdRP encoded by an unidentified viral gene.
细胞质DNA病毒编码一种依赖DNA的RNA聚合酶（DdRP），它对于病毒基因的转录至关重要。已知DdRPs的大亚基氨基酸序列包含高度保守区域。从两个保守结构域[RQP(T/S)LH和NADFDGDE]推导而来的寡核苷酸引物用于PCR实验，以检测昆虫虹彩病毒6型（也称为稻纵卷叶螟虹彩病毒，CIV）基因组的相应基因。大约150 bp的特异性DNA产物能够被扩增出来，并用作针对CIV基因文库的杂交探针来鉴定相应基因。编码DdRP的基因在CIV DNA的EcoRI片段M（7099 bp）和L（7400 bp）内被鉴定出来，位于图谱单位0.310和0.347（7990 bp）之间。确定了编码DdRP最大亚基（RPO1）的基因的DNA核苷酸序列（3153 bp）。Northern印迹杂交显示在CIV感染的细胞中存在一个与CIV DdRP基因杂交的3.4 kb RNA转录本。这个预测的病毒蛋白由1051个氨基酸残基（120K）组成，与真核RNA聚合酶II的最大亚基的相似性明显高于与痘苗病毒和非洲猪瘟病毒的同源蛋白的相似性。系统发育分析表明，CIV的假定RPO1可能在三种真核RNA聚合酶分化后从RNA聚合酶II进化而来。CIV的假定RPO1缺乏在真核、真细菌和其他病毒RNA聚合酶中保守的C末端结构域，在这方面类似于古细菌的RNA聚合酶。据推测，C末端结构域的等效物可能存在于由一个未鉴定的病毒基因编码的CIV DdRP的另一个亚基中。
