The kinase MK2 in DNA replication upon genotoxic stress and chemotherapy

Köpper, Frederik

dc.contributor.advisor	Dobbelstein, Matthias Prof. Dr.	de
dc.contributor.author	Köpper, Frederik	de
dc.date.accessioned	2013-01-14T15:06:30Z	de
dc.date.available	2013-10-17T22:50:04Z
dc.date.issued	2013-01-11	de
dc.identifier.uri	http://hdl.handle.net/11858/00-1735-0000-000D-EF92-6	de
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-1445
dc.description.abstract	DNA-Schäden stellen eine ständige Bedrohung der Genomintegrität dar. In Zellen haben sich von einem komplexen Signalnetzwerk kontrollierte Programme entwickelt, um mit diesen Läsionen zurechtzukommen und zu verhindern, dass Tumore entstehen. Diese zellulären Prozesse und die von ihnen regulierten Signalkaskaden bilden die Antwort auf DNA-Schäden (engl.: DNA damage response, DDR). Während viele Aspekte der DDR bis ins Detail untersucht worden sind, ist wenig darüber bekannt, wie Zellen auf genotoxischen Stress während der DNA-Replikation reagieren. Wir stellen in dieser Arbeit eine bislang unbekannte Funktion der Kinase MK2 in der Kontrolle der Replikation nach genotoxischem Stress während der S-Phase vor. MK2 ist ursprünglich als Mediator der allgemeinen Signaltransduktion nach Stress identifiziert worden, neuere Studien berichten jedoch von einer MK2-Funktion in der checkpoint-Signalisierung. In unserem Labor wurde bereits entdeckt, dass MK2 für die effiziente Phosphorylierung der Histon-Variante H2AX (genannt γH2AX), einem Kennzeichen der DDR, nach Schädigung der DNA durch ultraviolette (UV) Strahlung notwendig ist. Dieser Befund weist	de
dc.format.mimetype	application/pdf	de
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/	de
dc.title	The kinase MK2 in DNA replication upon genotoxic stress and chemotherapy	de
dc.type	doctoralThesis	de
dc.title.translated	Die Kinase MK2 in der DNA-Replikation nach genotoxischem Stress und Chemotherapie	de
dc.contributor.referee	Dobbelstein, Matthias Prof. Dr.	de
dc.date.examination	2012-10-17	de
dc.subject.dnb	570 Biowissenschaften, Biologie	de
dc.subject.gok	WF 200	de
dc.description.abstracteng	DNA damage constitutes a constant threat to genomic integrity. Cells evolved programs controlled by a complex signaling network to cope with these lesions in order to avoid tumorigenesis. These cellular processes and the signaling cascades that regulate them form the DNA damage response (DDR). Whereas many aspects of the DDR have been investigated in great detail, comparably little is known about how cells respond to genotoxic stress during DNA replication. Here, we identify a hitherto unknown function for the kinase MK2 in the control of replication upon genotoxic stress in S-phase. Originally described as a mediator of general stress signaling in the p38/MK2 pathway, recent studies reported a role of MK2 in checkpoint signaling. In our lab MK2 was previously found to be required for efficient phosphorylation of the histone variant H2AX (yielding γH2AX), a hallmark of the DDR, upon DNA damage induced by ultraviolet (UV) irradiation. This suggests a more general function of the kinase in the DDR than anticipated. We now report that depletion or inhibition of MK2 protects cells from the consequences of UV-induced DNA damage, and mice with genetic ablation of MK2 and its relative MK3 display strongly reduced apoptosis in the skin after UV irradiation. As UV-induced DNA damage mainly affects cells during replication but also in other phases of the cell cycle, we tested whether DNA damage induced by the S-phase-specific drug gemcitabine elicited an MK2-dependent DDR, as well. We found that inhibition or depletion of MK2 indeed reduces the accumulation of γH2AX and increases cell viability following gemcitabine treatment, and this effect cannot be attributed to cell cycle modulation by MK2. MK2 inhibition also rescues slow replication fork progression and increased origin firing caused by gemcitabine, demonstrating that the kinase affects replication in response to DNA damage in S-phase. We furthermore observed that MK2 is required for the genotoxic effects caused by inhibition or depletion of the essential checkpoint kinase Chk1 and that MK2 inhibition also alleviates deregulated replication caused by inhibition of Chk1. Such antagonistic activity between the two kinases comes as a surprise as both share the same target phosphorylation motif. We speculate that MK2 and Chk1 target different proteins, mediated by specific interaction partners not shared between the two. In search for the mechanism underlying the effect of MK2 on replication, we did not find any influence on regulators of origin firing, arguing that MK2 acts directly at the replication fork. The rescue of gemcitabine-induced slow fork speed by MK2 inhibition suggests that the kinase controls lesion bypass mechanisms. Accordingly, we observed that the rescue of deregulated replication by MK2 inhibition depends on translesion synthesis (TLS). We speculate that MK2 directly targets components of the TLS machinery, thereby repressing TLS. In conclusion, our data for the first time reveal an activity of MK2 in replication upon DNA damage. MK2 is required for slow fork speed and increased origin firing upon replicative stress, and this activity depends on TLS. We propose that MK2 balances the DDR by repressing TLS to limit the mutagenic effects of this lesion bypass mechanism, promoting DNA repair or cell death. These findings also identify the p38/MK2 pathway as a potential drug target as enhanced MK2 activation might sensitize cells to chemotherapy.	de
dc.contributor.coReferee	Wienands, Jürgen Prof. Dr.	de
dc.subject.topic	Biology (incl. Psychology)	de
dc.subject.ger	MK2	de
dc.subject.ger	MAPKAPK2	de
dc.subject.ger	p38	de
dc.subject.ger	replikativer Stress	de
dc.subject.ger	ultraviolette Strahlung	de
dc.subject.ger	Gemzitabin	de
dc.subject.ger	Nukleosid-Analoga	de
dc.subject.ger	Chemotherapie	de
dc.subject.ger	DNA-Replikation	de
dc.subject.ger	Transläsions-Synthese	de
dc.subject.ger	PCNA	de
dc.subject.ger	Chk1	de
dc.subject.ger	ATR	de
dc.subject.ger	H2AX	de
dc.subject.eng	MK2	de
dc.subject.eng	MAPKAPK2	de
dc.subject.eng	p38	de
dc.subject.eng	replicative stress	de
dc.subject.eng	ultraviolet irradiation	de
dc.subject.eng	gemcitabine	de
dc.subject.eng	nucleoside analogues	de
dc.subject.eng	chemotherapy	de
dc.subject.eng	DNA replication	de
dc.subject.eng	translesion synthesis	de
dc.subject.eng	PCNA	de
dc.subject.eng	Chk1	de
dc.subject.eng	ATR	de
dc.subject.eng	H2AX	de
dc.subject.bk	42.13	de
dc.identifier.urn	urn:nbn:de:gbv:7-webdoc-3870-1	de
dc.identifier.purl	webdoc-3870	de
dc.affiliation.institute	Biologische Fakultät	de
dc.description.embargoed	2013-04-16	de
dc.identifier.ppn	773354808

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