Chlamydia trachomatis developmentally regulated protein is homologous to eukaryotic histone H1.

Abstract

Chlamydiae are prokaryotic obligate intracellular parasites that undergo a biphasic life cycle involving an infectious, extracellular form known as elementary bodies and an intracellular, replicating form termed reticulate bodies. We have purified from Chlamydia trachomatis a very basic elementary body-specific protein with an apparent molecular mass of 18 kDa, determined its N-terminal amino acid sequence, and cloned the encoding gene. Sequence analysis of the cloned gene revealed some remarkable properties for its expressed product, including a high lysine content (29%), a correspondingly high pl, and significant homology to the Hi class of eukaryotic histones. Furthermore, a monoclonal antibody to this chlamydial histone analog, termed Hc1, displayed immunoblot and antinuclear specificity suggestive of cross-reactivity to Hi histones. The gene was expressed only during the late stages of the chlamydial life cycle concomitant with the reorganization of chlamydial reticulate bodies into elementary bodies, suggesting that the Hc1 protein plays a role in the condensation of chlamydial chromatin during intracellular differentiation.Chlamydiae are bacterial obligate intracellular parasites that possess several characteristics making them unique among prokaryotes. During their intracellular development they undergo dramatic morphological and functional changes (1). Infection of susceptible cells is initiated by a small, dense, and relatively metabolically inert elementary body (EB). By about 8 hr after infection, EBs differentiate to larger, more pleomorphic, and metabolically active reticulate bodies (RBs). Ultrastructurally, the EBs appear as spheres about 0.3

Chlamydial SET domain protein functions as a histone methyltransferase

“…It is a similar expression pattern of Hc1 and Hc2 proteins encoded by hctA and hctB genes, respectively (Hackstadt et al, 1991).…”

“…However, little is known about the switching mechanism whereby vegetative RBs convert into infectious EBs or aberrant RBs. Understanding this molecular system should be helpful for the prevention of persistent chlamydial infection.Two eukaryotic histone H1-like proteins of chlamydiae, Hc1 and Hc2, are present mainly in EBs, where those proteins bind DNA and promote genomic DNA condensation (Barry et al, 1992;Hackstadt et al, 1991;Perara et al, 1992;Tao et al, 1991). Recently a small regulatory RNA gene was identified as a suppressor of the lethal phenotype of hctA overexpression in Escherichia coli and it was shown to negatively regulate Hc1 synthesis at an early stage of infection (Grieshaber et al, 2006 HEp-2 cells (ATCC CCL-23) were used as host cells for infection by C. pneumoniae J138, isolated in Japan in 1994 (Shirai et al, 2000).…”

Chlamydia trachomatis protein GrgA activates transcription by contacting the nonconserved region of σ 66

“…Given that GrgA bound DNA in a sequence-nonspecific manner and could activate transcription from the defA promoter, we next determined if the transcription activation activity of GrgA was limited to the defA gene. Accordingly, we assessed the effects of GrgA in vitro on the activities of three additional σ 66 -dependent promoters that are active at different stages of growth: ribosomal RNA promotor P1 (rRNA P1; early), major outer membrane protein A (ompA; middle), and histone-like protein A (hctA; late) (8,9,19,20). GrgA demonstrated significant stimulatory effects on all of the three promoters (Fig.…”

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

“…SDS/polyacrylamide gels and Western blots were carried out as described (5). The anti-Hcl antiserum, a rabbit polyclonal antiserum raised to the purified 18-kDa protein from the L2 serovar of C. trachomatis (8) One hundred forty-six nucleotides beyond the termination codon for ORF1 is a second coding region (ORF2) that encodes a highly repetitive, alanine-and lysine-rich 207-amino acid residue polypeptide (Fig. 2).…”