Cloning and sequence analyses of the genes coding for the integration host factor (IHF) and HU proteins of Pseudomonas aeruginosa

Abstract

Histone-like proteins, such as HU and the integration host factor (IHF), are small, dimeric, DNA-bending proteins which play a role in maintaining constrained DNA structures and hence in regulating gene expression. Two different strategies were used to isolate the genes coding for Pseudomonas aeruginosa (Pa) HU and IHF, two proteins that we have previously isolated from a mucoid strain. By use of a PCR-based technique with oligodeoxyribonucleotides (oligos) designed from the N-terminal amino acid (aa) sequences of HU and the beta-subunit of IHF, and Southern blot analyses, hupB and himD, encoding HU and IHF beta, respectively, have been cloned. The himA gene of Pa, encoding the alpha-subunit of IHF, was isolated using himA of Escherichia coli (Ec) as a probe in Southern blot analyses. The deduced hupB product (90 aa, 9 kDa) is 79% identical to HU beta and 61% to HU alpha of Ec. The predicted products of himA (100 aa, 11.5 kDa) and of himD (94 aa, 10.6 kDa) share 77 and 70% identity with IHF alpha and IHF beta of Ec, respectively. The promoter region of himD contains an IHF consensus sequence, as is the case for Ec himD.