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In situ transcription and splicing in the Balbiani ring 3 gene
Author(s) -
Wetterberg Ingela,
Zhao Jian,
Masich Sergej,
Wieslander Lars,
Skoglund Ulf
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.10.2564
Subject(s) - rna splicing , spliceosome , intron , rna polymerase ii , biology , transcription (linguistics) , gene , splicing factor , minor spliceosome , group ii intron , microbiology and biotechnology , gene expression , rna , genetics , promoter , linguistics , philosophy
The Balbiani ring 3 (BR3) gene contains 38 introns, and more than half of them are co‐transcriptionally excised. We have determined the in situ structure of the active BR3 gene by electron tomography. Each of the 20–25 nascent transcripts on the gene is present together with splicing factors and the RNA polymerase II in a nascent transcript and splicing complex, here called the NTS complex. The results indicate that extensive changes in overall shape, substructure and molecular mass take place repeatedly within an NTS complex as it moves along the gene. The volume and calculated mass of the NTS complexes show that, maximally, one complete spliceosome is assembled on the multi‐intron transcript at any given time point. The structural data show that the spliceosome is not a structurally well‐defined unit in situ and that the C‐terminal domain of the elongating RNA polymerase II cannot carry spliceosomal components for all introns in the BR3 transcript. Our data indicate that spliceosomal factors are continuously added to and released from the NTS complexes during transcription elongation.