Study On The Temporal Expression Of Sulfolobus Virus STSV2 Genes During Infection

Sulfolobus is a model for archaea genetic mechanism research,and its viruses have obtained more attention.As Sulfolobus is a powerful tool for research of archaea,study on the characteristic of their viruses will help to understand the genomic structure,origin and evolution of viruses.A novel Sulfolobus virus named STSV2 was isolated from Tengchong hot springs.STSV2 was a typical spindle virus with a spindle head(220×80nm),a long flexible tail with 20-100nm at one end and the average length of about 50nm.Sulfolobus H5-2 was also isolated from Tengchong hot springs with spherical,irregular polyhedron cells and its diameter is about 1.0 ?m?1.2 ?m with a single flagellum.The optimum growth temperature is 80 ?,the optimum growth pH is 3.1.Sulfolobus could form a smooth flat dark yellow colony on solid media.In this study,Sulfolobus H5-2 and virus STSV2 were used to study the characteristic of STSV2 genome,the structure analysis and expression validation of STS V2 operons,the temporal expression of STSV2 genes during infection and the interaction between virus and host.Here we first analyzed the structure of STSV2 genome.Total 75 ORFs were found,which were divided into two halves arranging on the genome,indicating that the major half of genes were transcribed in one direction,while the rest half of genes were transcribed in the opposite direction.50%of the gene-encoded proteins of STSV2 shared homology to those from other species.Among them,20%of the proteins shared homology to those from archaea,and 15%and 7%to those from bacteria and fungi with,respectively.Gene functional annotation rusults revealed that these encoded proteins potentially involved DNA replication,recombination,repair,nucleic acid metabolism,transcription and coding structural protein,but there was no coding sequence of RNA polymerase on the STSV2 genome.Furthermore,X seven operons on the STSV2 genome were predicted and seven operons were experimentally verified.Promoter analysis results also showed that the characteristics of the promoters were similar that of eukaryotes,but they also have typical prokaryotic SD sequence.Some promoters were featured with a--TTTAAATA--or--CTTTT--sequence at about 30bp upstream region of transcription starting site containing,Some were featured with a--AGAAAGTTTTA--sequence at about 30bp upstream region of transcription starting site,and the others did not showed clear sequence characteristics.By studying the temporal expression of Sulfolobus virus STSV2 genes during infection,the highest transcript level for all ORFs at 72 h after infection was observed,but slightly increase followed by decrease at 48h and 168h respectively,was also observed for most ORFs.The growth of host is inhibited significantly during infection.Rifampicin can firmly combine with RNA polymerase? subunit of prokaryote,inhibiting competitivly the synthesis of bacterial RNA.Rifampicin also inhibited the mRNA expression of STSV2 genes in our test,which indicted that virus STSV2 uses host RNA polymerase for gene transcription after infection.Furthermore,infection of STSV2 could increase the expression levels of host genesIn this study,the temperate archaeal virus STSV2 was used to study the temporal expression of its genes during infection,and the rule of temporal regulation was concluded by combining with promoter characteristic ofSTSV2.This is helpful to reveal the transcripted regulation of virus STSV2 gene in the process of infection,and it also provide a reference to study the origin of archaea and virus,evolution and diversity.