Universität zu Köln

Krause, Anke (2014). Posttranslationale Modifikation des Proteins der Promyelozytenleukämie (PML) nach unterschiedlicher Stressinduktion. PhD thesis, Universität zu Köln.

Preview

PDF Diss_ohne_CV.pdf Download (5MB)

Abstract

Posttranslational modifications such as sumoylation, ubiquitination or phosphorylation regulate multiple functions of the promyelocytic leukemia protein (PML) also the morphology of PML nuclear bodies. In this study, the influence of different stress factors as arsenic trioxide (ATO) and sorbitol on endogenous and overexpressed PML has been analysed to investigate the STUbL (sumo-targeted ubiquitin ligase) - signalling pathway of RNF4 (RING finger protein 4). Sumoylation of PML is a key regulator of PML stability in response to extracellular or intracellular stimuli. This study shows PML degradation via polysumoylation induced by ATO, a therapeutic agent for treatment of acute promyelocytic leukemia (APL). Sumoylated PML is targeted for ubiquitination by the E3 ligase RNF4 prior to the proteasome-mediated degradation. Furthermore, I was able to demonstrate that RNF4 interacts with PML as substrate in vivo using its two essential SIMs, SIM2 and SIM4. In contrast to ATO sorbitol treatment leads to increased PML-nuclear bodies (PML-NBs) in number and size and to a stabilization of PML, which is not affected by the inhibition of the 26S proteasome. Due to the discrepancy between the effects of ATO and sorbitol on PML and PML-NBs, the activity of cellular signalling cascades has been analysed upon those stress factors. After quantitative analysis of kinases, there is evidence that osmotic stress leads to the activation of the SAPK/JNK (Stress-activated Protein Kinase/Jun Nterminal Kinase) - and ERK (Extracellular-signal Regulated Kinase ) - signalling pathways. In conclusion, ATO leads to the proteolytic degradation of PML due to its sumodependant ubiquitination mediated by RNF4. So I assume, that in contrast to ATO, after osmotic stress PML is stabelized through its own phosphorylation via the SAPK/JNK- and the ERK-signalling cascade.