CONGRATULATIONS TO OUR NEW DOCTOR, Lana Bosanac, who graduated with the Congratulations of the jury !



Lana BOSANAC presented her PhD defense on November 24th 2010 at ENS, Département de Biologie, Salle Favard

Thesis title : "Nuclear Factor Dynamics : Regulation of Gene Expression by Nuclear Targeting of P-TEFb"

Members of the jury :
François Taddei, Directeur de recherche, INSERM, president of the Jury
Robert Tjian, Professor, UC Berkeley
Arnaud Poterszman, Directeur de recherche, CNRS/IGBMC
Bernard Vandenbunder, Directeur de recherche, CNRS/IRI
Olivier Bensaude, Directeur de recherche, INSERM/ENS
Xavier Darzacq, chargé de recherche, CNRS/ENS
Raphaël Voituriez, chargé de recherche, CNRS/UPMC

Abstract :
Proteins engaged in macromolecular complexes interacting with chromatin move throughout the nucleus by diffusive processes, transiently and repetitively contacting their target sites. Diffusion and interactions play important roles in gene expression by defining the target gene search time. We monitored the mobility of the Positive Transcription Elongation factor b (P-TEFb) responsible for the phosphorylation of the RNA polymerase II C-terminal domain and showed that its relatively high mobility is regulated by the 7SK small nuclear ribonucleoprotein complex (7SK snRNP). Without the 7SK regulating complex, transient interactions of the P-TEFb cycline T1 component with RNA polymerase II prevent the nuclear distribution of the elongation factor therefore restricting its activity to sites of high polymerase concentration and limiting its recruitment to new sites. This observation demonstrates that the fast mobility of proteins required for the stochastic assembly of nuclear molecular machines is not only a physical property of macromolecules but a biophysical parameter tightly controlled by cellular regulators.