The Role Of Lysine Acetylation In Regulating Replication Initiation And Ribosome Activity

DNA replication and protein translation processes are the basis of genetic information transmission and expression and they are very important for bacteria.Studies of bacterial acetylome shows that many proteins involved in replication and translation are acetylated,but their biological significance are less understood.Based on our previously work,we select replication innitiator DnaA and ribosomal proteins to elucidate the physiological relevance between lysine acetylation and replication as well as translation.DNA replication initiation is a central event in the cell cycle and this process has to occur at the correct time.Multiple mechanisms regulate this process at the initiation stage.In this study,we found DnaA K243 was a critical acetylated lysine residue by plasmid complementation test.In vitro and in vivo studies both implied the acetylation level of K243 were regulated by CobB and AcP and correlated with intracellular AcP concentration.When this residue was acetylated,DnaA had decreased affinity for the replication origin(oriC)but retained the binding activities to ATP/ADP,dnaA promoter and DARS sequence.A DNase I footprinting assay further revealed that DnaA failed to recognize DnaA boxes I3,C1,and C3 when K243 was acetylated.The incomplete initiation complex had defect in DNA unwinding and replication innitiation.To determine the biological function of acetylation on ribosomal proteins,we first performed a systematic research on the acetylome of ribosomal proteins.Results showed that almost all ribosomal proteins were acetylated and their acetylation level were regulated by Pat、CobB and AcP.Besides,we noticed that ribosomal proteins have higher acetylation level when cells entered into stationary phase,at which time,the synthesis of ribosomes are declined.Thus,we speculated that acetylation may be involved in the regulation of ribosome biogenesis.Next,we screened several candidates which have critical roles in the interaction with ribosomal RNA.Results implyed that when these sites were mutated to mimic acetylation,it has effect on their RNA binding activities.Furthermore,the assembly of ribosome changed in ΔcobB and ΔackA strains.These findings provide new insights into the regulatory mechanisms of replication and translation.