An IL-4/IL-13 dual antagonist reduces lung inflammation, airway hyperresponsiveness, and IgE production in mice

IL-4 and IL-13 comprise promising targets for therapeutic interventions in asthma and other Th2-associated diseases, but agents targeting either IL-4 or IL-13 alone have shown limited efficacy in human clinical studies. Because these cytokines may involve redundant function, dual targeting holds promise for achieving greater efficacy. We describe a bifunctional therapeutic targeting IL-4 and IL-13, developed by a combination of specific binding domains. IL-4-targeted and IL-13-targeted single chain variable fragments were joined in an optimal configuration, using appropriate linker regions on a novel protein scaffold. The bifunctional IL-4/IL-13 antagonist displayed high affinity for both cytokines. It was a potent and efficient neutralizer of both murine IL-4 and murine IL-13 bioactivity in cytokine-responsive Ba/F3 cells, and exhibited a half-life of approximately 4.7 days in mice. In a murine model of ovalbumin-induced ear swelling, the bifunctional molecule blocked both the IL-4/IL-13-dependent early-phase response and the IL-4-dependent late-phase response. In the ovalbumin-induced lung inflammation model, the bifunctional IL-4/IL-13 antagonist reduced the IL-4-dependent rise in serum IgE titers, and reduced IL-13-dependent airway hyperresponsiveness, lung inflammation, mucin gene expression, and serum chitinase responses. Taken together, these findings demonstrate the effective dual blockade of IL-4 and IL-13 with a single agent, which resulted in the modulation of a more extensive range of endpoints than could be achieved by targeting either cytokine alone.

Initiation and regulation mechanisms of ribosomal RNA transcription in the eukaryote Acanthamoeba castellanii

Acanthamoeba rRNA transcription involves the binding of a transcription initiation factor (TIF) to the core promoter of rDNA to form the preinitiation complex. This complex is formed in the absence of RNA polymerase I, and persists for multiple rounds of initiation. Polymerase I next binds to form the initiation complex. This binding is DNA sequence-independent, and is directed by protein-protein contacts with TIF. DNA melting occurs in a separate step. In contrast to most prokaryotic transcription, melting occurs only following nucleotide addition and beta-gamma hydrolysis of ATP is not required as for polymerase II. Growth-dependent regulation of rRNA transcription is accomplished by modification of RNA polymerase I. The inactive form of polymerase (PolE) is unable to bind to the promoter and has altered heat stability. PolE is still active in elongation; thus, the modification affects the polymerase site involved in TIF contact. Modification of a polymerases I and III common subunit has been detected leading to the suggestion that transcription of stable RNAs of the ribosome might be co-regulated by this mechanism.

The 5'-flanking sequences of Drosophila melanogaster tRNA5Asn genes differentially arrest RNA polymerase III

Three tRNA5Asn genes have been subcloned from a tRNA gene cluster isolated from the cytogenetic locus 42A of Drosophila melanogaster. The three tRNAAsn genes, contained on plasmids pAsn6, pAsn7, and pAsn8, have identical mature tRNA coding regions but have different 5'- and 3'-flanking sequences. In vitro transcription in Drosophila Schneider S3 cell-free extracts showed the tRNAAsn genes had different transcription efficiencies. pAsn8 had a transcription efficiency of approximately 8 transcripts/gene/h, whereas pAsn6 was a less active template at 5 transcripts/gene/h. pAsn7 was the poorest template at 1.5 transcripts/gene/h. Exchanging 5'-flanking regions of the tRNAAsn genes showed that the differences in transcription efficiencies were attributable to the corresponding 5'-flanking region. Transcription of each of the tRNAAsn genes revealed a different optimum for KC1 concentration for each template which also was directly attributable to the corresponding 5'-flanking region. The "salt effect" is not related to the ability of the three tRNAAsn genes to sequester transcription factors as determined using the stable complex competition assay. Rather, this effect appears to be due to the ability of the respective 5'-flanking regions to interact with RNA polymerase III. The poorest transcription template, pAsn7, was a better competitor in the stable complex formation assay than either pAsn8 or pAsn6. We conclude that the pAsn7 stable complex binds and functionally arrests RNA polymerase III in the initiation reaction.