Bridging the Double-Strand Break Process

Jason Liang

Appointment Period: 2011-2013, Grant Years: [27,28]

My current research project is a focused and on examining how cells regulate the processing of DNA double-stranded breaks (DSB). Upon DNA double-stranded break, cells are known to coordinate its repair through an assembly of multiple DNA repair enzymes, which I hypothesize to be regulated by the Mec1 and Tel1 kinases. I found that Sae2, a protein involved in processing DNA double stranded-breaks, physically interacts with the MRX complex, a heterotrimeric protein complex known to be involved in the initial sensing of broken DNA ends. I found that this physical interaction is mediated by Mec1/Tel1-dependent phosphorylation of Sae2 and is specific to the Xrs2 subunit of the MRX complex. Moreover, I have constructed a phosphorylation-defective mutant of Sae2 and begun to investigate its genetic interactions and in vivo functional consequences using yeast genetics and cell biology. Having set up the biochemical assay to study these interactions I intend to take one step further and identify and characterize additional DNA repair enzymes involved in DNA DSB repair. In this way, my goal is to elucidate the role of Mec1 and Tel1 in regulating the DNA DSB repair process, which likely contributes to the chromosomal defects observed for cells deficient in these kinases.

I plan to continue studying the DNA damage signaling pathway in mammals, where human orthologs have been implicated in several cancer-prone diseases, including Njimegen breakage syndrome and ataxia telangiecstasia. Understanding these molecular mechanisms in yeast and extrapolating to humans will allow the possibility for a deeper understanding of double-strand break repair in cancer.

PUBLICATIONS (resulting from this training)

Narasimha AN, Shapiro GS, Hagopian JC, Liang J, Albuquerque CP, Zhou H, Dowdy SF. Activation of Rb by Mono-Phosphorylation Regulates DNA Damage Responses. Cell (2012) In Review.

Other publications (prior to Training Grant appointment):

Zhou H, Albuquerque CP, Liang J, Suhandynata RT, Weng S. Quantitative phosphoproteomics: New technologies and applications in the DNA damage response. Cell Cycle. 2010 Sep 1;9(17):3479-84. Epub 2010 Sep 26. Review. PubMed PMID: 20855976.

Chen SH, Albuquerque CP, Liang J, Suhandynata RT, Zhou H. A proteome-wide analysis of kinase-substrate network in the DNA damage response. J Biol Chem. 2010 Apr 23;285(17):12803-12. Epub 2010 Feb 27. PubMed PMID: 20190278; PubMed Central PMCID: PMC2857137.