论文部分内容阅读
乙型肝炎病毒(HBV)含环状部分双链DNA,由约3200碱基对组成,是具有最小基因组的 DNA 病毒。在其负链上,重迭有编码前-S(表面)/S 基因、前-C(核心)/C 基因、多聚酶基因和 X 基因的四个开放读码框架(ORF)。最近,经计算机分析发现,还存在另外两个ORF(即 ORF5和 ORF6,其中 ORF6存在于正链上),但其产物目前还不太清楚。关于该病毒的 RNA 转录本,现已知有3.5kb(前基因组,核心和多聚酶)、2.4kb(前-S_1、S_2和 S)及2.1kb(前-S_2、S)三种,在它们的3′-末端均以多聚腺苷酸位点(poly-Asite)结尾。此外,体外实验还发现有编码 X 蛋白的约0.7kb 的 RNA,但活体内情况尚有诸多不明之处。HBV 的复制具有明显的特点。即 HBV 虽属 DNA 病毒,但却可通过逆转录从前基因组RNA 来合成 DNA,这是非常独特之处。在感染肝细胞后,即在肝细胞内修复其单链缺口区,进入细胞核内,转变成共价闭合环状(cov-alently closed circular,CCC)DNA,随后转录病毒 RNA,即产生前基因组 RNA,将蛋白引物及逆转录酶一起包装进核心粒子,接着合成负链及正链 DNA,再包以表面抗原,即生成病毒粒子,向细胞外释放。此外,一部分可通过再循环重新进入细胞核内,以 CCC 分子形式蓄积起来。与逆转录病毒大相庭径的是,HBV 虽可整合进宿主 DNA 内,但对病毒的复制并非必需。可能当病毒正常形成和复制不能顺利进行时,病毒 DNA 即在核内蓄积,并整合进宿主 DNA。HBV 并不含有癌基因,那么它是通过什
Hepatitis B virus (HBV) contains circular partial double-stranded DNA, consisting of about 3200 base pairs, and is the DNA virus with the smallest genome. On the minus strand, there are four open reading frames (ORFs) overlapping the pre-S (surface) / S gene, the pre-C (core) / C gene, the polymerase gene and the X gene. Recently, another two ORFs (ie, ORF5 and ORF6, in which ORF6 is present on the plus strand) were found by computer analysis, but the products are not yet clear. About the RNA transcripts of this virus, there are three known RNA transcripts of 3.5 kb (pregenome, core and polymerase), 2.4 kb (pre-S_1, S_2 and S) and 2.1 kb (pre-S2 and S) The 3’-terminus ends with poly-Asite. In addition, in vitro experiments also found about 0.7kb RNA encoding X protein, but there are still many in vivo unknown situation. HBV replication has obvious characteristics. Although HBV is a DNA virus, it can synthesize DNA by reverse transcription of pre-genomic RNA, which is very unique. After infection with hepatocytes, that is, repairing its single-stranded gap region in hepatocytes, into the nucleus, into cov-alently closed circular (CCC) DNA, followed by transcription of the viral RNA, the generation of pre-genomic RNA , The protein primer and reverse transcriptase together packaged into the core particle, then the synthesis of negative and positive strand DNA, and then coated with surface antigen, that is, the generation of virus particles, released to the outside of the cell. In addition, a portion can re-enter the nucleus by recycling, accumulating as CCC molecules. In contrast to retroviruses, HBV integrates into host DNA, but is not necessary for virus replication. It is possible that when normal virus formation and replication can not proceed smoothly, the viral DNA accumulates in the nucleus and integrates into the host DNA. HBV does not contain oncogenes, then it is through