ICP22 HOMOLOG OF EQUINE HERPESVIRUS-1 - EXPRESSION FROM EARLY AND LATE PROMOTERS
ICP22 HOMOLOG OF EQUINE HERPESVIRUS-1 - EXPRESSION FROM EARLY AND LATE PROMOTERS
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DOI：
10.1128/jvi.66.2.664-673.1992
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发表时间：
1992-02-01
影响因子：
5.4
通讯作者：
OCALLAGHAN, DJ
中科院分区：
文献类型：
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作者：
HOLDEN, VR;YALAMANCHILI, RR;OCALLAGHAN, DJ
马疱疹病毒1型（EHV-1）基因组的短片段（6.5kb）由一对反向重复序列（IR，各12.8kb）包围而成，其完整的核苷酸序列已在本实验室测定。IR片段的分析揭示了指定为IR 4的主要开放阅读框架（ORF）。IR 4 ORF与单纯疱疹病毒1型的立即早期基因US 1（ICP 22）以及水痘-带状疱疹病毒（ORF 63）、伪狂犬病病毒（RSp 40）和马疱疹病毒4型（ORF 4）的ICP 22同源物具有显著的同源性。IR 4 ORF完全位于每个反向重复序列（核苷酸[nt] 7918至9327）内，并具有编码469个氨基酸（49，890 Da）的多肽的潜力。在IR 4 ORF内有两个重复序列：串联重复17次的7-nt序列和串联重复13次的25-nt序列。IR 4的核苷酸序列分析还揭示了几个潜在的顺式调节序列，两个TATA序列由287 nt分开，每个TATA序列后的框内翻译起始密码子，和一个单一的多聚腺苷酸化位点。为了解决由IR 4编码的mRNA种类的性质，我们使用北方（RNA）印迹和S1核酸酶分析。RNA图谱数据显示，IR 4有两个启动子，在裂解感染过程中受到差异调节。一个1.4 kb的mRNA最初出现在感染后2小时，是一个早期的转录本，因为它的合成不受膦酰乙酸，EHV-1 DNA复制的抑制剂的存在。相比之下，1.7 kb的mRNA出现在感染后较晚的时间，并被指定为γ-1转录本，因为其合成显着减少膦酰基乙酸。这些IR 4特异性mRNA是3'共末端的，具有独特的5'末端，并且将分别编码293和469个氨基酸的框内、重叠、羧基共末端蛋白。有趣的是，产生启动持续感染的EHV-1缺陷性干扰颗粒基因组的同源重组位点发生在UL 3的nt 3244和3251（ICP 27同源物）与IR 4的nt 9027和9034（ICP 22同源物）之间。因此，该重组事件将产生独特的ORF，该ORF将编码潜在的蛋白质，该蛋白质的氨基端衍生自ICP 22同系物的N-末端193个氨基酸，并且其羧基端衍生自ICP 27同系物的C-末端68个氨基酸。
The complete nucleotide sequence of the short region, made up of a unique segment (Us; 6.5 kb) bracketed by a pair of inverted repeat sequences (IR; 12.8 kb each), of the equine herpesvirus 1 (EHV-1) genome has been determined recently in our laboratory. Analysis of the IR segment revealed a major open reading frame (ORF) designated IR4. The IR4 ORF exhibits significant homology to the immediate-early gene US1 (ICP22) of herpes simplex virus type 1 and to the ICP22 homologs of varicella-zoster virus (ORF63), pseudorabies virus (RSp40), and equine herpesvirus 4 (ORF4). The IR4 ORF is located entirely within each of the inverted repeat sequences (nucleotides [nt] 7918 to 9327) and has the potential to encode a polypeptide of 469 amino acids (49,890 Da). Within the IR4 ORF are two reiterated sequences: a 7-nt sequence tandemly repeated 17 times and a 25-nt sequence tandemly repeated 13 times. Nucleotide sequence analyses of IR4 also revealed several potential cis-regulatory sequences, two TATA sequences separated by 287 nt, an in-frame translation initiation condon following each TATA sequence, and a single polyadenylation site. To address the nature of the mRNA species encoded by IR4, we used Northern (RNA) blot and S1 nuclease analyses. RNA mapping data revealed that IR4 has two promoters that are regulated differentially during a lytic infection. A 1.4-kb mRNA appears initially at 2 h postinfection and is an early transcript since its synthesis is not affected by the presence of phosphonoacetic acid, an inhibitor of EHV-1 DNA replication. In contrast, a 1.7-kb mRNA appears at later times postinfection and is designated as a gamma-1 transcript, since its synthesis is significantly reduced by phosphonoacetic acid. These IR4-specific mRNAs are 3' coterminal, have unique 5' termini, and would code for in-frame, overlapping, carboxy-coterminal proteins of 293 and 469 amino acids, respectively. Interestingly, the site of homologous recombination to generate the genome of EHV-1 defective interfering particles that initiate persistent infection occurs between nt 3244 and 3251 of UL3 (ICP27 homolog) and nt 9027 and 9034 of IR4 (ICP22 homolog). Thus, this recombination event would generate a unique ORF that would encode a potential protein whose amino end was derived from the N-terminal 193 amino acids of the ICP22 homolog and whose carboxyl end was derived from the C-terminal 68 amino acids of the ICP27 homolog.