论文部分内容阅读
Promoters are modular DNA structures containing complex regulatory elements required for gene transcription initiation.In prokaryotes,the sigma(σ)factor of RNA holoenzyme plays key roles in recognizing and binding to the promoter sequences during gene transcription.Thus,the types of prokaryotic promoters are defined according to the types of σ factor.Two families of σ factors,namely σ70 family and σ54 family,determine promoter specificity.The σ70 promoters commonly contain three basic regulatory elements: Pribnow box(or called TATA box)with consensus TATAAT around-10 bp upstream of transcription start site(TSS),-35 box with consensus TTGACA around-35 bp upstream of TSS and initiator(Inr)around TSS.The σ54 factor can recognize the unique regulatory elements with the consensus sequence TGC[AT][TA] around-12 bp and [CT]TGGCA[CT][GA] around-24 bp upstream of the TSS.Although the biochemical experimental approaches can provide the details for prokaryotic promoters,the wet-experimental technique is time-consuming and expensive.With the avalanche of biological sequences generated in the postgenomic era,it is highly desirable to develop computational methods to identify prokaryotic promoters in prokaryotic genomes.