Journal
NUCLEUS
Volume 3, Issue 3, Pages 290-299Publisher
TAYLOR & FRANCIS INC
DOI: 10.4161/nucl.20327
Keywords
profilin; polytene chromosomes; gene expression; immunofluorescence; immuno-electron microscopy; nuclear actin
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Funding
- Swedish Research Council (Vetenskapsradet)
- Research School for Genomics and Bioinformatics at the Stockholm University
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We have raised antibodies against the profilin of Chironomus tentans to study the location of profilin relative to chromatin and to active genes in salivary gland polytene chromosomes. We show that a fraction of profilin is located in the nucleus, where profilin is highly concentrated in the nucleoplasm and at the nuclear periphery. Moreover, profilin is associated with multiple bands in the polytene chromosomes. By staining salivary glands with propidium iodide, we show that profilin does not co-localize with dense chromatin. profilin associates instead with protein-coding genes that are transcriptionally active, as revealed by co-localization with hnRNP and snRNP proteins. We have performed experiments of transcription inhibition with actinomycin D and we show that the association of profilin with the chromosomes requires ongoing transcription. however, the interaction of profilin with the gene loci does not depend on RNA. Our results are compatible with profilin regulating actin polymerization in the cell nucleus. however, the association of actin with the polytene chromosomes of C. tentans is sensitive to RNase, whereas the association of profilin is not, and we propose therefore that the chromosomal location of profilin is independent of actin.
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