ABSTRACT
The influenza NS1 protein is involved in suppression of the host immune response. Recently, there is growing evidence that prion-like protein aggregation plays an important role in cellular signaling and immune responses. In this work, we obtained a recombinant, influenza A NS1 protein and showed that it is able to form amyloid-like fibrils in vitro. Using proteolysis and subsequent mass spectrometry, we showed that regions resistant to protease hydrolysis highly differ between the native NS1 form (NS1-N) and fibrillar form (NS1-F); this indicates that significant structural changes occur during fibril formation. We also found a protein fragment that is capable of inducing the process of fibrillogenesis at 37 °C. The discovery of the ability of NS1 to form amyloid-like fibrils may be relevant to uncovering relationships between influenza A infection and modulation of the immune response.
Subject(s)
Amyloid/metabolism , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolism , Congo Red/chemistry , Congo Red/metabolism , Kinetics , Microscopy, Atomic Force , Microscopy, Electron , Models, Molecular , Protein Aggregates , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/isolation & purification , Recombinant Proteins/metabolism , Viral Nonstructural Proteins/chemistryABSTRACT
Chromatin assembly is a fundamental process that is essential for chromosome duplication subsequent to DNA replication. In addition, histone removal and incorporation take place constantly throughout the cell cycle in the course of DNA-utilizing processes, such as transcription, damage repair or recombination. In vitro chromatin assembly requires the concerned action of histone chaperones and ATP-utilizing chromatin assembly factors. ATP-dependent chromatin assembly and remodeling factor CHD1 (Chromo-ATPase/Helicase-DNA-binding protein 1) is involved in multiple cellular processes, such as the replication independent assembly of nucleosomes containing the variant histone H3.3, regulation of transcription initiation, elongation and termination; determination of steam cell pluripotency and in cancer development. We have shown that mutations in Drosophila Chd1 gene induce a decondensation of the male X chromosome, similar to that induced by mutations in the iswi nucleosome remodeling factor. An effect of Chd1 null mutation can be increased by deficiency of one of the genes, encoding variant histone H3.3, His 3.3 B, suggesting that the role of CHD1 in the control of male X chromosome organization can be mediated by CHD1 activity in H3.3 histone deposition and exchange.