A procaryotic regulatory factor with a histone H1-like carboxy-terminal domain: clonal variation of repeats within algP, a gene involved in regulation of mucoidy in Pseudomonas aeruginosa

Abstract

A novel procaryotic transcriptional regulatory element, AlgP, with a histone Hl-like carboxy-terminal domain was identified in Pseudomonas aeruginosa. AlgP is required for transcription of the key biosynthetic gene algD, which is necessary for production of the exopolysaccharide alginate causing mucoidy in P. aeruginosa. Mucoidy is a critical virulence determinant of P. aeruginosa invariably associated with the respiratory infections causing high mortality in cystic fibrosis. Here we show that AlgP and histones Hi both have repeated units of the Lys-Pro-Ala-Ala motif (KPAA) and its variations within their long (over 100 amino acids) carboxy-terminal domains. This region of histone Hi tails has been shown to bind to the linker DNA in eucaryotic chromatin fibers. A synthetic 50-mer peptide consisting of repeats from the AlgP carboxy-terminal domain was found to bind DNA in a mobility shift DNA-binding assay. AlgP is encoded by a gene that contains multiple direct repeats organized as tandem, head-to-tail, 12-base-pair (bp) units overlapping with six highly conserved 75-bp units. The repetitive structure of the algP gene appears to participate in the processes underlying the metastable character of mucoidy in P. aeruginosa. Relatively large DNA rearrangements spanning the region with tandem direct repeats encoding the carboxy-terminal histone Hl-like structure of AlgP were detected in several strains upon conversion from the mucoid to the nonmucoid phenotype. The frequency of the detectable algP rearrangements associated with the transition into the nonmucoid state varied from strain to strain and ranged from 0 to 50%. The nonmucoid derivatives with the clearly rearranged chromosomal copy of algP were complemented to mucoidy with plasmids containing algP from P. aeruginosa PAO. When a random collection of mucoid strains, isolated from different cystic fibrosis patients, was analyzed by using polymerase chain reaction, an additional level of strain-dependent sequence variation in algP was observed. Variations in the number of the 12-bp repeats were found; however, they did not appear to influence the mucoid status of the strains examined. Thus, the repeated region of algP appears to be a hot spot for DNA rearrangements and strain-dependent variability.

A developmentally regulated chlamydial gene with apparent homology to eukaryotic histone H1.

“…This protein is involved in positively regulating the biosynthesis of the exopolysaccharide alginate and has been shown to bind directly to a specific DNA sequence (15). AlgR3 contains many repeats of the PAAK motif in its C terminus and itself shows almost 50% identity with the painted sea urchin histone H1 over a 150-amino acid region (15).…”

“…AlgR3 contains many repeats of the PAAK motif in its C terminus and itself shows almost 50% identity with the painted sea urchin histone H1 over a 150-amino acid region (15). Synthetic peptides composed of the PAAK motif of AlgR3 have been shown by gel shift mobility experiments to bind DNA in a sequence-specific manner (15). We have recently discovered that synthetic peptides containing three or four repeats of the KKTVA pentapeptide present in KARP will also bind in a sequence nonspecific manner to double-stranded DNA oligonucleotides as assayed by gel shift mobility experiments (J.N.E., unpublished results).…”

Molecular cloning and expression of hctB encoding a strain-variant chlamydial histone-like protein with DNA-binding activity

“…Data base searches employing the BLAST program (1) revealed high scoring similarities with a number of DNAbinding proteins, including AlgP, a regulator of alignate synthesis in Pseudomonas aeniginosa (9,10,20), and the principal RNA polymerase sigma factor hrdB of Streptomyces coelicolor (35). The common feature shared by virtually all protein sequences retrieved is an activity involving interaction with nucleic acids.…”

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“…These units are organized in six segments each consisting of six KPAA repeats separated by a spacer (Gly or Ala) ( Fig. 2A; Deretic and Konyecsni, 1990). The similarities of AlgP with histones HI underscore the presence of KPAA units within the histone tails as well.…”

“…This involves an unusual genetic element, algP (Deretic et ai, 1989a;Konyecsni and Deretic, 1990;Deretic and Konyecsni, 1990) (alternative name algR3: Kato ef ai, 1990), which encodes a basic polypeptide with a repetitive structure. The carboxytermina!…”