ORGANIZATION AROUND THE DNAA GENE OF STREPTOCOCCUS-PNEUMONIAE

The dnaA gene region of Streptococcus pneumoniae was cloned and sequen ced. A tRNA gene, seven ORFs and three DnaA box clusters were identifi ed. The order of the genes and intergene regions found was tRNA(Arg)-o rf1-DnaA box cluster 3-htrA-spo0J-DnaA box cluster 2-dnaA-DnaA box clu ster 1-dnaN-orfX-orfY. Five ORFs are homologous to known bacterial gen es. The tRNA(Arg) gene and orf1, also called orfL, have already been d escribed in pneumococci and have been reported to be preceded by the c ompetence regulation locus comCDE. In Escherichia coli, htrA encodes a serine protease. In Bacillus subtilis, spo0J plays a role in sporulat ion and partition. dnaA encodes an initiator replication protein, very well conserved in several bacteria and dnaN encodes the beta subunit of DNA polymerase III in E. coli. The function of orfX is unknown. The N-terminal part of another reading frame, orfY, revealed high homolog y with a GTP-binding protein. DnaA box clusters were found upstream an d downstream from dnaA. The presence of two such clusters suggests tha t the chromosomal origin of S. pneumoniae is located within this regio n. The position of dnaA, and therefore the putative origin of replicat ion, were localized on the physical map of S. pneumoniae.