title: The in vivo dynamics of TCERG1, a factor that couples transcriptional elongation with splicing.
abstract: Coupling between transcription and RNA processing is key for gene regulation. Using live-cell photobleaching techniques, we investigated the factor TCERG1, which coordinates transcriptional elongation with splicing. We demonstrate that TCERG1 is highly mobile in the nucleoplasm and that this mobility is slightly decreased when it is associated with speckles. Dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) but not α-amanitin treatment reduced the mobility of TCERG1, which suggests interaction with paused transcription elongation complexes. We found that TCERG1 mobility is rapid at the transcription site (TS) of a reporter that splices post-transcriptionally and that TCERG1 is recruited to the active TS independent of the CTD of RNAPII, thus excluding phosphorylated CTD as a requirement for recruiting this factor to the TS. Importantly, the mobility of TCERG1 is reduced when the reporter splices cotranscriptionally, which suggests that TCERG1 forms new macromolecular complexes when splicing occurs cotranscriptionally. In this condition, spliceostatin A has no effect, indicating that TCERG1 rapidly binds and dissociates from stalled spliceosomal complexes and that the mobility properties of TCERG1 do not depend on events occurring after the initial spliceosome formation. Taken together, these data suggest that TCERG1 binds independently to elongation and splicing complexes, thus performing their coupling by transient interactions rather than by stable association with one or the other complexes. This finding has conceptual implications for understanding the coupling between transcription and RNA processing.
authors.affiliation: Department of Molecular Biology, Instituto de Parasitología y Biomedicina "López Neyra" (IPBLN-CSIC), PTS, Granada 18016, Spain.
authors.forename: Noemí
authors.initials: N
authors.lastname: Sánchez-Hernández
authors.affiliation: Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique, 34293 Montpellier, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Boireau
authors.affiliation: Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique, 34293 Montpellier, France.
authors.forename: Ute
authors.initials: U
authors.lastname: Schmidt
authors.affiliation: Department of Molecular Biology, Instituto de Parasitología y Biomedicina "López Neyra" (IPBLN-CSIC), PTS, Granada 18016, Spain.
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Muñoz-Cobo
authors.affiliation: Department of Cell Biology and Immunology, Instituto de Parasitología y Biomedicina "López Neyra" (IPBLN-CSIC), PTS, Granada 18016, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Hernández-Munain
authors.affiliation: Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique, 34293 Montpellier, France.
authors.forename: Edouard
authors.initials: E
authors.lastname: Bertrand
authors.affiliation: Department of Molecular Biology, Instituto de Parasitología y Biomedicina "López Neyra" (IPBLN-CSIC), PTS, Granada 18016, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Suñé
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D017930:Genes, Reporter; D057809:HEK293 Cells; D015497:HIV-1 / Q000235:genetics; D006801:Humans; D021381:Protein Transport; D012326:RNA Splicing; D061805:Transcription Elongation, Genetic; D035602:Transcriptional Elongation Factors / Q000502:physiology*
chemical_list: C108440:TCERG1 protein, human; D035602:Transcriptional Elongation Factors
keywords: FRAP; HIV; RNAPII; splicing; transcription site; transcription–splicing coupling