The phage N4 virion RNA polymerase catalytic domain is related to single-subunit RNA polymerases

In vitro, bacteriophage N4 virion RNA polymerase (vRNAP) recognizes in vivo sites of transcription initiation on single-stranded templates. N4 vRNAP promoters are comprised of a hairpin structure and conserved sequences. Here, we show that vRNAP consists of a single 3500 amino acid polypeptide, and we define and characterize a transcriptionally active 1106 amino acid domain (mini-vRNAP). Biochemical and genetic characterization of this domain indicates that, despite its peculiar promoter specificity and lack of extensive sequence similarity to other DNA-dependent RNA polymerases, mini-vRNAP is related to the family of T7-like RNA polymerases.

体外实验中，噬菌体N4病毒体RNA聚合酶（bacteriophage N4 virion RNA polymerase，vRNAP）可识别单链模板上的体内转录起始位点。N4 vRNAP启动子由发夹结构与保守序列共同构成。本研究证实，vRNAP由一条3500个氨基酸的多肽链组成，并对一个具备转录活性的1106氨基酸结构域（mini-vRNAP）进行了定义与表征。对该结构域开展的生化与遗传表征结果显示，尽管其具有独特的启动子特异性，且与其他依赖DNA的RNA聚合酶缺乏广泛的序列相似性，但mini-vRNAP仍属于类T7 RNA聚合酶家族。