A new role of CDKS in the control of replication fork progression by checkpoint kinase

GONZÁLEZ MG, HABIF M, MANSILLA SF, VALLERGA MB, FEDERICO MB, GOTTIFREDI VG

Mar del Plata

Congreso; SAIB ? 51th Annual Meeting - Argentine Society for Biochemistry and Molecular Biology.; 2015

SAIB

A new role of CDKS in the control of replication fork progression by checkpoint kinase Marina A. González, Martín Habif, Sabrina Mansilla, María B. Vallerga, María B. Federico, Vanesa Gottifedi.Fundación Instituto Leloir. Av. Patricias Argentinas 435 (CP C1405BWE). Buenos Aires, Argentina.The encounter of replication forks with DNA lesions activate Checkpoint Kinase 1 (Chk1) which stabilizes forks and inhibits late origin firing. While the mechanisms that underlie Chk1-dependent inhibition of origin firing have been elucidated, the molecular signals that impair the progression of replication forks in Chk1-depleted samples remains largely unexplored. We observed that roscovitine, a CDK (cyclin-dependent kinase) inhibitor, rescues the afore-mentioned siChk1-dependent phenotypes. Others have proposed that roscovitine restores the progression of active forks by reducing origin firing and making the nucleotide pool available for DNA elongation. However, we provide evidence showing that this is not the case since a reduction in origin firing back to wild-type levels in cells lacking Chk1 (by means other than roscovitine) does not translate into efficient DNA elongation.Reinforcing the notion of a direct role of CDKs in fork progression, we show that such roscovitine-induced elongation of DNA requires Pol, an alternative polymerase that copies damaged DNA. Indeed, the DNA elongation defect caused by siChk1 transfection is rescued by forcing Polto replication forks. In conclusion, our study suggests that Chk1 signals via CDKs not only to inhibit origin firing but also by promoting Poldependent fork stabilization.