No abstract

The multifunctional DNA-and RNA-associated Y-box protein 1 (YB-1) specifically binds to splicing recognition motifs and regulates alternative splice site selection. Here, we identify the arginine/serine-rich SRp30c protein as an interacting protein of YB-1 by performing a two-hybrid screen against a human mesangial cell cDNA library. Co-immunoprecipitation studies confirm a direct interaction of tagged proteins YB-1 and SRp30c in the absence of RNA via two independent protein domains of YB-1. A high affinity interaction is conferred through the N-terminal region. We show that the subcellular YB-1 localization is dependent on the cellular SRp30c content. In proliferating cells, YB-1 localizes to the cytoplasm, whereas FLAG-SRp30c protein is detected in the nucleus. After overexpression of YB-1 and FLAG-SRp30c, both proteins are co-localized in the nucleus, and this requires the N-terminal region of YB-1. Heat shock treatment of cells, a condition under which SRp30c accumulates in stress-induced Sam68 nuclear bodies, abrogates the co-localization and YB-1 shuttles back to the cytoplasm. Finally, the functional relevance of the YB-1/SRp30c interaction for in vivo splicing is demonstrated in the E1A minigene model system. Here, changes in splice site selection are detected, that is, overexpression of YB-1 is accompanied by preferential 5 splicing site selection and formation of the 12 S isoform.The Y-box protein YB-1 is a member of the cold shock protein family, which exhibits pleiotropic functions. YB-1 specifically binds to a sequence motif termed Y-box. This motif is characterized by the presence of a core ATTGG sequence, which represents the inverted CCAAT-box. YB-1 controls the transcription of numerous genes that among others include MHC class II antigen, MDR1, MMP-2, and COL1A1 (1-4). DNA binding specificity is mediated through the evolutionarily conserved cold shock domain in conjunction with the adjacent C-terminal protein residues (5, 6). Interactions of YB-1 with numerous cellular and viral transcription factors including JC virus antigen (7), AP-2 (8), Pur␣ (9), CTCF (10), and p53 (11, 12) have been demonstrated. These interactions may in part explain cell-specific gene regulation, that is, stimulation and repression of transcription, even of the same gene (3). In addition, it has been proposed that YB-1 plays a role as an architectural protein by its propensity to sequence specifically unwind DNA duplexes and stabilize single-stranded templates, thereby altering sequence recognition motifs (1,4,8).In addition to their role in regulating gene transcription, cold shock proteins exhibit a wide spectrum of activities by virtue of sequence-specific and -nonspecific RNA binding. YB-1 has been identified as the major component of messenger ribonucleoprotein particles (mRNPs) in mammalian cells, which constitute templates for the translational machinery (13-15). At higher concentrations Y-box proteins Xenopus FRGY2 and human YB-1 act as repressors of translation in a process called mRNA masking (13, 16 -18), wh...

No abstract

Mesh biocompatibility is basically determined by the foreign body reaction (FBR). In contrast to physiological wound healing and scar formation, the FBR at the host-tissue/biomaterial interface is present for the lifetime of the medical device. The cellular interactions at the mesh/tissue interface proceed over time ending up in a chronic inflammatory process. The time course of the FBR has been studied extensively and consists of three crucial steps that are protein absorption, cell recruitment and, finally, fibrotic encapsulation and extracellular matrix formation. Each of these steps involves a complex cascade of immune modulators including soluble mediators and various cell types. Recent research has focused on the cellular and molecular interactions of the distinct phases of the FBR offering a new basis for therapeutical strategies. The highly dynamic process of the FBR is considerably influenced by the biomaterial composition. Modifications of the type of polymer, the material weight, the filament structure and the pore size are realized and have substantial effects on the in vivo biocompatibility. Moreover, modern mesh technology aims to utilize the available implants as carrier systems for bioactive drugs. Studies in animal models account for the efficiency of these drugs that aim to reduce mesh-related infections or to minimize FBR by influencing inflammation or extracellular matrix remodelling. A thorough understanding of the molecular mechanisms of FBR provides a sophisticated background for the development of new biomaterials at least as carrier systems for bioactive reagents to reduce inflammation and to improve clinical outcome.

No abstract