Breeden C A, Yalamanchili R R, Colle C F, O'Callaghan D J
Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932.
Virology. 1992 Dec;191(2):649-60. doi: 10.1016/0042-6822(92)90240-p.
Two open reading frames (ORFs) encoded at the inverted repeat unique short (Us) junction of the Short (S) region of the equine herpesvirus type 1 genome were identified by DNA sequencing of a 2876 base pair (bp) genomic segment, and transcripts encoding these ORFs were characterized by Northern blot, S1 nuclease, and primer extension analyses. These studies also established the size of each inverted repeat to be 12,768 nucleotides (nts). The IR6 ORF (816 bp), mapping at nts 12,317-11,502 of the S region, is the last gene completely encoded within each inverted repeat and encodes a predicted 30.1-kDa protein of 272 amino acids, which does not exhibit homology to other alphaherpesvirus proteins. IR6 is expressed as an early transcript of 1.2 kb which is detected initially at 1.5 hr p.i. and up to 12 hr p.i. The transcription initiation and termination sites of IR6 were mapped by primer extension and S1 nuclease analyses to nts 12,465 and 11,408, respectively. The first ORF encoded within the Us segment (909 bp; EUS1), mapping at nts 13,397-12,489, encodes a predicted 33.5-kDa protein of 303 amino acids that exhibits 29% identity to the US2 protein of herpes simplex virus 1. EUS1 is expressed as a 2.3-kb mRNA of the gamma-1 class, as its synthesis begins prior to viral DNA replication at 4 hr p.i. but is retarded by phosphonoacetic acid, an inhibitor of viral DNA replication. The Tci and Tct sites of EUS1 were mapped by S1 nuclease analyses to nts 13,637 and 11,408, respectively. Interestingly, this termination site is also utilized by three late mRNAs of 5.8, 3.8, and 1.7 kb which originate within the Us and overlap the IR6 mRNA encoded in the terminal inverted repeat (TR) of the prototype genomic isomer. EUS1 is 3' coterminal with IR6 in the inverted repeat, whereas, the 5.8, 3.8, and 1.7 kb transcripts are 3' coterminal with IR6 of the TR.
通过对一段2876个碱基对（bp）的基因组片段进行DNA测序，在1型马疱疹病毒基因组短（S）区域的反向重复独特短序列（Us）连接处鉴定出两个开放阅读框（ORF），并通过Northern印迹、S1核酸酶和引物延伸分析对编码这些ORF的转录本进行了表征。这些研究还确定每个反向重复序列的大小为12,768个核苷酸（nts）。IR6开放阅读框（816 bp）位于S区域的nts 12,317 - 11,502处，是每个反向重复序列内完全编码的最后一个基因，编码一个预测的由272个氨基酸组成的30.1 kDa蛋白质，该蛋白质与其他α疱疹病毒蛋白没有同源性。IR6作为一个1.2 kb的早期转录本表达，最初在感染后1.5小时检测到，直至感染后12小时。通过引物延伸和S1核酸酶分析，将IR6的转录起始和终止位点分别定位到nts 12,465和11,408。Us片段内编码的第一个开放阅读框（909 bp；EUS1）位于nts 13,397 - 12,489处，编码一个预测的由303个氨基酸组成的33.5 kDa蛋白质，与单纯疱疹病毒1的US2蛋白具有29%的同一性。EUS1作为γ-1类的2.3 kb mRNA表达，因为其合成在感染后4小时病毒DNA复制之前开始，但受到病毒DNA复制抑制剂膦甲酸的抑制。通过S1核酸酶分析将EUS1的Tci和Tct位点分别定位到nts 13,637和11,408。有趣的是，这个终止位点也被5.8、3.8和1.7 kb的三个晚期mRNA使用，它们起源于Us区域并与原型基因组异构体末端反向重复序列（TR）中编码的IR6 mRNA重叠。在反向重复序列中，EUS1与IR6在3'端共末端，而5.8、3.8和1.7 kb的转录本与TR的IR6在3'端共末端。
