Processing of pre-mRNA in polytene nuclei of Chironomus tentans salivary gland cells.
Salivary gland polytene cells in the dipteran Chironomus tentans provide exceptional experimental possibilities to analyze processing of specific pre-mRNAs in intact eukaryotic cell nuclei. Here we give a brief account of how these experimental advantages can be exploited to analyze the splicing process in vivo. In multi-intron pre-mRNAs, spliceosomes assemble and splicing is initiated cotranscriptionally for all introns. Intron excision may, however, occur mainly co- transcriptionally or mainly posttranscriptionally depending on the position of each intron in relation to the remaining transcription time and intron-specific efficiencies of excision. As measured for the U2 snRNP and an SR protein, 10-15% of the spliceosomal components are bound to pre-mRNA at active gene loci at a given moment, while the majority of the spliceosomal components are present in the nucleoplasm. A continuous redistribution of the spliceosomal components takes place in the nucleus as a result of a close coupling between transcription and spliceosomal assembly.
Wieslander
L
L
Department of Radiobiology, Stockholm University, Stockholm, S-106 91, Sweden.
Baurén
G
G
Bernholm
K
K
Jiang
W Q
WQ
Wetterberg
I
I
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002683:Chironomidae / Q000235:genetics / Q000378:metabolism*; D007438:Introns; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D012469:Salivary Glands / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism
D012322:RNA Precursors