562015-03-24 , 法政大学大学院理工学・工学研究科
Escherichia coli have a sophisticated genetic system for adaptation to changes in external environment by selective transcription of a total of about 4,500 genes on its genome. The functional distribution of RNA polymerase determines the transcription pattern of the genome by the two-step differentiation of RNA polymerase. In the first step, one of seven sigma factors binds to the RNA polymerase core enzyme with the subunit structure ααββ’ω to form the holoenzyme, which recognize specific promoters. In the second step, the RNA polymerase interacts with regulatory proteins. In E. coli, amino acid starvation increases the level of ppGpp, called alarmone, to modulate transcription of genes involved in protein synthesis and amino acid biosynthesis, which called the stringent response. ppGpp and DksA together inhibit transcription by RNA polymerase. On the other hand, glucose-limitation is known to increase the level of cAMP, which binds to CRP to regulate gene expression. RP-IP shut-gun analysis, newly developed to identify the set of proteins of RNA polymerase complex, showed that DksA stimulated the formation of RNA polymerase containing ω subunit, which causes the stability of interaction between RNA polymerase and CRP. These suggest that stringent response alarmone ppGpp affect the adaptation of carbon starvation by the functional differentiation of RNA polymerase by DksA and CRP.