Histone Sin mutations promote nucleosome traversal and histone displacement by RNA polymerase II
ABSTRACT Nucleosome traversal by RNA polymerase II (pol II) and recovery of chromatin structure after transcription are essential for proper gene expression. In this paper we show that nucleosomes assembled with Sin mutant histones present a much weaker barrier to traversal by pol II and are less likely to survive transcription. Increases in traversal from incorporation of Sin mutant histones and histones lacking H2A/H2B amino-terminal tails were in most cases additive, indicating that traversal can be facilitated by distinct mechanisms. We had identified a key intermediate in traversal, the zero (slashed circle)-loop, which mediates nucleosome survival during transcription. Sin mutations probably destabilize these intermediates and thus increase the likelihood of nucleosome disassociation.
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Conference Paper: Digital libraries settling the score: 10 years hence and 10 before.ACM/IEEE Joint Conference on Digital Libraries, JCDL 2004, Tucson, AZ, USA, June 7-11, 2004, Proceedings; 01/2004
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ABSTRACT: Creating, maintaining, or using a digital library requires the manipulation of digital documents. Information workspaces provide a visual representation allowing users to collect, organize, annotate, and author information. The visual knowledge builder (VKB) helps users access, collect, annotate, and combine materials from digital libraries and other sources into a personal information workspace. VKB has been enhanced to include direct search interfaces for NSDL and Google. Users create a visualization of search results while selecting and organizing materials for their current activity. Additionally, metadata applicators have been added to VKB. This interface allows the rapid addition of metadata to documents and aids the user in the extraction of existing metadata for application to other documents. A study was performed to compare the selection and organization of documents in VKB to the commonly used tools of a Web browser and a word processor. This study shows the value of visual workspaces for such effort but points to the need for subdocument level objects, ephemeral visualizations, and support for moving from visual representations to metadata.ACM/IEEE Joint Conference on Digital Libraries, JCDL 2004, Tucson, AZ, USA, June 7-11, 2004, Proceedings; 01/2004