Dpb11 may function with RPA and DNA to initiate DNA replication

Signaling pathways involved in cell cycle arrest during the DNA breaks

Our genome bears tens of thousands of harms and devastations per day; In this regard, numerous sophisticated and complicated mechanisms are embedded by our cells in furtherance of remitting an unchanged and stable genome to their next generation. These mechanisms, that are collectively called DDR, have the duty of detecting the lesions and repairing them. it's necessary for the viability of any living cell that sustain the integrity and stability of its genetic content and this highlights the role of mediators that transduce the signals of DNA damage to the cell cycle in order to prevent the replication of a defective DNA. In this paper, we review the signaling pathways that lie between these processes and define how different ingredients of DDR are also able to affect the checkpoint signaling.

Preparation of endogenous TopBP1/Dpb11 and effect on central checkpoint kinase Mec1- Ddc2 (human ATR-ATRIP homolog)

The Saccharomyces cerevisiae Mec1 kinase, the mammalian ATR ortholog, is essential for sensing a variety of DNA lesions and initiating DNA damage response. The Dpb11, a homolog of human TopBP1, functions in activating the Mec1 upon DNA replication stress and DNA damages. Here, we report an affinity purification and ion exchange chromatography method to efficiently purify endogenous Dpb11 under normal expression level directly from yeast whole cell extraction. The final concentration of 5 μM of high purity and homogeneity biochemical preparation enables functional and structural characterization of the physical interaction between Dpb11 and Mec1-Ddc2 complex. The Dpb11 obtained by endogenous purification strongly stimulates the Mec1 kinase activity and promotes the changes in conformational distribution. This observation suggests the Dpb11 activates Mec1 kinase probably through modulation in the kinase conformations.