Regulation of hnRNP K and 4E-BP1 in response to DNA damage. (360G-Wellcome-082609_A_07_Z)

This collaborative project will investigate mechanisms regulating the stability and functions of two proteins involved in a network of transcriptional and translational control during the cellular stress response to DNA damage. The proteins in question are the DNA-and RNA-binding protein heterogeneous nuclear ribonucleoprotein K (hnRNPK) and the translational regulatory factor eIF4E-binding protein 1 (4E-BP1). Current evidence indicatesthat the phosphorylation of hnRNPK is enhanced, and that of 4E-BP1 decreased, during the DNA damage response. Both proteins are substrates for ubiquitination and proteasome-mediated degradation and their stability is increased by DNA damage. Our preliminary data suggest that ATM-dependent phosphorylation of hnRNPK and mTOR-dependent phosphorylation of 4E-BP1 have opposite effects on ubiquitination, resulting in a coordinated inhibitory effect on the turnover of the two proteins. Key goals will therefore be to investigate the phosphorylation events critical for the ubiquitination of hnRNP K and 4E-BP1, characterise the ubiquitin ligase(s) that modify 4E-BP1, and study the consequences of ubiquitination of the two proteins for their stability and role in the DNA damage response. We will also analyse the mechanisms by which DNA damage controls the pathways involved and will investigate the regulatory network involving hnRNPK and 4E-BP1 that centres onthe translation factor eIF4E.