ABSTRACT
The transcriptional silencing of one of the female X-chromosomes is a finely regulated process that requires accumulation in cis of the long non-coding RNA X-inactive-specific transcript (Xist) followed by a series of epigenetic modifications. Little is known about the molecular machinery regulating initiation and maintenance of chromosomal silencing. Here, we introduce a new version of our algorithm catRAPID to investigate Xist associations with a number of proteins involved in epigenetic regulation, nuclear scaffolding, transcription and splicing processes. Our method correctly identifies binding regions and affinities of protein interactions, providing a powerful theoretical framework for the study of X-chromosome inactivation and other events mediated by ribonucleoprotein associations.
Subject(s)
Algorithms , RNA, Long Noncoding/metabolism , RNA-Binding Proteins/metabolism , X Chromosome Inactivation , Animals , Binding Sites , Enhancer of Zeste Homolog 2 Protein , Female , Heterogeneous-Nuclear Ribonucleoprotein U/metabolism , Matrix Attachment Region Binding Proteins/metabolism , Mice , Nuclear Proteins/metabolism , Polycomb Repressive Complex 2/metabolism , RNA, Long Noncoding/chemistry , Repetitive Sequences, Nucleic Acid , Serine-Arginine Splicing Factors , YY1 Transcription Factor/metabolismABSTRACT
The aggregation of misfolded proteins is a common feature underlying a wide range of age-related degenerative disorders, including Alzheimer's and Parkinson's diseases. A key aspect of understanding the molecular origins of these conditions is to define the manner in which specific types of protein aggregates influence disease pathogenesis through their interactions with cells. We demonstrate how selenium-enhanced electron microscopy (SE-EM), combined with tomographic reconstruction methods, can be used to image, here at a resolution of 5-10 nm, the interaction with human macrophage cells of amyloid aggregates formed from Aß(25-36), a fragment of the Aß peptide whose self-assembly is associated with Alzheimer's disease. We find that prefibrillar aggregates and mature fibrils are distributed into distinct subcellular compartments and undergo varying degrees of morphological change over time, observations that shed new light on the origins of their differential toxicity and the mechanisms of their clearance. In addition, the results show that SE-EM provides a powerful and potentially widely applicable means to define the nature and location of protein assemblies in situ and to provide detailed and specific information about their partitioning and processing.