Interphase chromatin is arranged into topologically separated domains comprising gene expression and replication units through genomic sequence elements so-called MAR or SAR regions (for matrix- or scaffold-associating regions). S/MAR regions are located near the boundaries of actively transcribed genes and were shown to influence their activity. We show that scaffold attachment factor B (SAF-B), which specifically binds to S/MAR regions, interacts with RNA polymerase II (RNA pol II) and a subset of serine-/arginine-rich RNA processing factors (SR proteins). SAF-B localized to the nucleus in a speckled pattern that coincided with the distribution of the SR protein SC35. Furthermore, we show that overexpressed SAF-B induced an increase of the 10S splice product using an E1A reporter gene and repressed the activity of an S/MAR flanked CAT reporter gene construct in vivo. This indicates an association of SAF-B with SR proteins and components of the transcription machinery. Our results describe the coupling of a chromatin organizing S/MAR element with transcription and pre-mRNA processing components and we propose that SAF-B serves as a molecular base to assemble a 'transcriptosome complex' in the vicinity of actively transcribed genes.
|Number of pages||8|
|Journal||Nucleic Acids Research|
|State||Published - Aug 1 1998|
Bibliographical noteFunding Information:
We thank C.Cap for help with sequencing, O.Georgiev for his contribution to the isolation of CTD interacting clones, J.Cáceres for the E1A construct and I.Sures and M.Stein-Gerlach for reading the manuscript. We also thank J.Chalcroft and Yuh-Shin Chang for technical assistance, and Walter Schaffner for support and helpful discussions. This work was supported by the Swiss National Science Foundation, the Kanton Zürich, the Max-Planck-Society, the Human Frontier Science Program RG-562/96 to S.S. and SUGEN.
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