The SR protein B52/SRp55 is required for DNA topoisomerase I recruitment to chromatin, mRNA release and transcription shutdown.
DNA- and RNA-processing pathways are integrated and interconnected in the eukaryotic nucleus to allow efficient gene expression and to maintain genomic stability. The recruitment of DNA Topoisomerase I (Topo I), an enzyme controlling DNA supercoiling and acting as a specific kinase for the SR-protein family of splicing factors, to highly transcribed loci represents a mechanism by which transcription and processing can be coordinated and genomic instability avoided. Here we show that Drosophila Topo I associates with and phosphorylates the SR protein B52. Surprisingly, expression of a high-affinity binding site for B52 in transgenic flies restricted localization, not only of B52, but also of Topo I to this single transcription site, whereas B52 RNAi knockdown induced mis-localization of Topo I in the nucleolus. Impaired delivery of Topo I to a heat shock gene caused retention of the mRNA at its site of transcription and delayed gene deactivation after heat shock. Our data show that B52 delivers Topo I to RNA polymerase II-active chromatin loci and provide the first evidence that DNA topology and mRNA release can be coordinated to control gene expression.
Juge
François
F
Institut de Génétique Moléculaire de Montpellier UMR 5535 CNRS, 1919 route de Mende, 34293 Montpellier cedex 5, France.
Fernando
Céline
C
Fic
Weronika
W
Tazi
Jamal
J
D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002843:Chromatin / Q000201:enzymology*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D029721:Drosophila Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000201:enzymology* / Q000235:genetics*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D009687:Nuclear Proteins / Q000172:deficiency / Q000378:metabolism*; D010750:Phosphoproteins / Q000172:deficiency / Q000378:metabolism*; D010766:Phosphorylation; D059007:Polytene Chromosomes / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D021381:Protein Transport; D000072260:RNA Splicing Factors; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D002843:Chromatin; D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; C544596:Hsp70Aa protein, Drosophila; D009687:Nuclear Proteins; D010750:Phosphoproteins; D000072260:RNA Splicing Factors; D012333:RNA, Messenger; C070791:B52 protein, Drosophila; D011494:Protein Kinases; D004264:DNA Topoisomerases, Type I