Identification and characterization of proteins that selectively interact with isoforms of the mRNA binding protein AUF1 (hnRNP D)

The mRNAs that encode certain cytokines and protooncogenes frequently contain a typical AU-rich motif that is located in their 3'-untranslated region. The protein AUF1 is the first factor identified that binds to AU-rich regions and mediates the fast degradation of the target mRNAs. AUF1 exists as four different isoforms (p37, p40, p42 and p45) that are generated by alternative splicing. The fact that AUF1 does not degrade mRNA itself had led to the suggestion that other AUF1 interacting proteins might be involved in the process of selective mRNA degradation. Here we used the yeast twohybrid system in order to identify proteins that bind to AUF1. We detected AUF1 itself, as well as the ubiquitinconjugating enzyme E2I and three RNA binding proteins: NSEP-1, NSAP-1 and IMP-2, as AUF1 interacting proteins. We confirmed all interactions in vitro and mapped the protein domains that are involved in the interaction with AUF1. Gelshift assays with the recombinant purified proteins suggest that the interacting proteins and AUF1 can bind simultaneously to an AU-rich RNA oligonucleotide. Most interestingly, the AUF1 interacting protein NSEP-1showed an endoribonuclease activity in vitro. These data suggest the possibility that the identified AUF1 interacting proteins might be involved in the regulation of mRNA stability mediated by AUF1.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.3841253

Reversal of the adult IgE high responder phenotype in mice by maternally transferred allergen-specific monoclonal IgG antibodies during a sensitive period in early ontogeny

IgE is an important trigger in allergy and asthma, diseases whose development is suggested to depend on an initial sensitization in early life. While induction of murine IgE responses requires both a genetically based IgE high responder phenotype and defined experimental conditions, maternally transferred IgG can override these prerequisites and suppress IgE formation in an allergen-specific manner. Here, we show that maternally transferred monoclonal IgG, irrespective of their subclass and recognized epitopes, induce IgE unresponsiveness, which is effective for parenteral immunization with bee venom phospholipase A² as well as for airway-immunization with nebulized ovonnucoid-containing ovalbumin. This IgE suppression is detectable in the offspring during the first 4 months of life, but not thereafter and not in the dams. However, when the initial immunization at an age of 3 or 4 months was followed by further application of both allergens via their respective routes, IgE suppression persisted up to an age of more than one year. If applicable to man, these findings may allow the development of a new strategy for the prevention of allergy and asthma by maternally transferred or neonatally injected allergen-specific mAb in combination with natural or prophylactic exposure to the respective allergens during early childhood