Chromatin remodelling in Pol I and III transcription
Abstract: Compaction of chromosomes in the eukaryotic cell is due to interactions between DNA and proteins and interactions between proteins. These two types of interaction form a dynamic structure, known as "chromatin". The condensation of chromatin must be carefully regulated, since the structure is an obstacle for factors that need access to the DNA. An extensive range of components, one group of which is the ATP-dependent chromatin remodel-ling complexes, controls the accessibility of DNA. These complexes have been studied in a variety of eukaryotic systems, and their functions in major events in the cell, such as replication, DNA-repair and transcription have been established, as have their roles in the assembly and maintenance of chromatin. All of the complexes contain a highly conserved ATPase, which belongs to the SWI2/SNF2 family of proteins, one group of which is known as the ISWI proteins. There are two forms of ISWI in human, known as "SNF2h" and "SNF2l".We have identified a human SNF2h-assembly, B-WICH, that consists of SNF2h, William’s syndrome transcription factor (WSTF), nuclear myosin (NM1), and a number of additional nuclear proteins including the Myb-binding protein 1a (Myb bp1a), SF3b155/SAP155, the RNA helicase II/Gu?, the proto-oncogene Dek, and the Cockayne Syndrome protein B (CSB). The 45S rRNA, 5S rRNA and 7SL RNA are all parts of the B-WICH assembly. The formation of B-WICH depends on active transcription, and is implicated in the regulation of both RNA transcription by both pol I and pol III. The B-WICH provides a link between RNA and the chromatin structure.
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