PrimeArray: genome-scale primer design for DNA-microarray construction

PrimeArray is a Windows program that computes oligonuceotide primer pairs for genome-scale gene amplification by the Polymerase Chain Reaction (PCR). The program supports the automated extraction of coding sequences (CDS) from various input-file formats and allows highly automated primer pair-optimization.

Construction of versatile high-level expression vectors for Bartonella henselae and the use of green fluorescent protein as a new expression marker

Expression vectors suitable for directing high levels of protein synthesis in Bartonella henselae have been constructed based on the mobilisable broad-host-range (IncQ) plasmidpMMB206. They confer kanamycin resistance and feature the taclac (tac-lacUV5 in tandem) promoters in front of a polylinker followed by the rrnB transcriptional stop point. While expression of genes fused to the taclac promoter is constitutive in one vector, the lacIq gene carried by the other vector allows a controlled, IPTG-inducible gene expression. These vectors were tested by subcloning a mutated gfp gene coding for the green fluorescent protein (GFP) from Aequorea victoria into the multiple cloning site and introducing the resulting plasmids into Escherichia coli and B. henselae. GFP expression was determined by measuring fluorescence via flow cytometry or directly by immunoblotting. Compared to E. coli, expression of GFP in B. henselae was more tightly controlled by lacIq and resulted in much higher levels of both IPTG-induced and constitutive gene expression. In vitro infection of endothelial cells indicated that GFP expression does not adversely affect the interaction of B. henselae with host cells. These data demonstrate that (i) the established expression vectors are useful for directing controlled or constitutive high-level protein synthesis in B. henselae and (ii) that GFP is a valuable expression marker which may has important applications in studying the bacterial genetics and cellular interactions of this emerging human pathogen.

Vitronectin-dependent invasion of epithelial cells by Neisseria gonorrhoeae involves alpha(v) integrin receptors

Binding of vitronectin (VN) to Neisseria gonorrhoeae expressing the heparan sulfate proteoglycan (HSPG) specific Opa50 protein was recently shown to trigger bacterial internalization into distinct epithelial cell lines. We have investigated the role of VN-binding integrin receptors and protein kinase C (PKC) in VN-triggered bacterial uptake. Blocking integrin function by RGDS peptides or by antibodies specific to alpha(v)beta5 or alpha(v)beta3 resulted in an abrogation of VN-triggered bacterial internalization. Moreover, inhibitors of PKC were found to block VN-triggered uptake. The essential role of alpha(v) integrins and the presumable involvement of PKC in VN-triggered gonococcal uptake are discussed.

Binding of vitronectin to opa-expressing Neisseria gonorrhoeae mediates invasion of HeLa cells

Neisseria gonorrhoeae induces local infections in the human genitourinary tract and can disseminate to other organs to cause severe disease. Blood-derived factors present in the genital mucosa have been suggested to facilitate the spread of N. gonorrhoeae in disseminated gonococcal infections. Using gentamicin invasion assays and confocal microscopy, we observed a strong stimulatory effect of fetal calf serum (FCS) on the gonococcal invasion of HeLa cells. FCS-mediated invasion was dependent on the expression of the epithelial cell invasion-associated Opa protein (plasmid-encoded Opa50 or its chromosomal homolog Opa30), while N. gonorrhoeae expressing noninvasive Opa proteins (Opa(51-60)) or no Opa protein (Opa-) was not invasive even in the presence of FCS. Incubation of N. gonorrhoeae MS11 with biotinylated FCS revealed a 78-kDa protein as the prominent protein binding to Opa50- or Opa30-expressing gonococci. This protein was recognized by antibodies against vitronectin (VN) in Western blots. Purified human or bovine VN efficiently bound to Opa50-expressing gonococci, while binding to noninvasive Opa- or Opa52-expressing gonococci was significantly lower. Binding of VN was inhibited by heparin in a concentration-dependent manner, indicating that the heparin binding sites present in VN or Opa50 may play an essential role in this interaction. Based on gentamicin invasion assays and confocal microscopy studies, VN binding was associated with an increased invasion of Opa50- and Opa30-expressing gonococci into HeLa cells. The ability of VN to mediate entry into epithelial cells may constitute an important event in the pathogenesis of local as well as disseminated gonococcal infections.

bHLH proteins encoded by the Enhancer of split complex of Drosophila negatively interfere with transcriptional activation mediated by proneural genes

The Enhancer of split complex [E(SPL)-C] of Drosophila participates in the control of cell fate choice by uncommitted neuroectodermal cells in the embryo. It encodes seven proteins that belong to the basic helix-loop-helix (bHLH) family, six of which are expressed in very similar patterns in the neuroectoderm. Here we describe experiments aimed at unravelling the molecular basis of their function. We found that two products of the complex, HLH-M5 and ENHANCER OF SPLIT, are capable of binding as homo-and heterodimers to a sequence in the promoters of the Enhancer of split and achaete genes, called the N-box, which differs slightly from the consensus binding site (the E-box) for other bHLH proteins. In transient expression assays in cell culture, both proteins were found to attenuate the transcriptional activation mediated by the proneural bHLH proteins LETHAL OF SCUTE and DAUGHTERLESS at the Enhancer of split promoter.