How are the major transitions in the cell division cycle controlled, and how might disruptions in that control affect genome stability? How do signaling pathways that control cell cycle progression (both intracellular and extracellular) affect DNA replication competence and regulation? Follow the link for “Research” to read more detailed background information.
Why do we care?
We are intensely curious about the eukaryotic cell cycle and how it is coordinated such that the chromosomes are fully duplicated at the appropriate time and then segregated to the two daughter cells. We wonder how cells manage to ensure that replication doesn’t occur under inappropriate circumstances, such as when the DNA is damaged or cells are exposed to novel stimuli. It's becoming increasingly clear that cancer cells initiate replication inappropriately and furthermore, that they do a "sloppy" job of precisely duplicating and segregating their genomes. We seek to determine how cell cycle transitions are normally controlled and how that control is disrupted in cancer cells. On the flipside, we want to know how cells ensure that replication is efficient so they can proliferate to replace damaged or old cells.
How do we figure it out?
We use a combination of biochemistry, cell biology, molecular biology, pharmacology, and genetics. We use cultured mammalian cells (both cancer cell lines and normal cells) and manipulate the proteins and signaling activities in those cells. We suppress expression of replication and signaling proteins by RNAi “knockdown,” inhibit enzyme activities with drugs, or overproduce proteins by transient transfection, retroviral insertion, or adenoviral infection. We measure protein abundance, chromatin localization, cell cycle progression, replication activity, protein-protein interactions, etc… We have active collaborations with many other cell cycle and DNA metabolism labs both at UNC and at other institutions.
What have we learned so far?
Most recently, we demonstrated a positive role for histone H3 lysine 4 di-methylation in origin function (Rizzardi et al., 2012), and we have catalogued some of the global changes in the human proteome at two cell cycle transitions (Lane et al., 2013). We made the surprising discovery that the Cdt1 replication protein is also required during mitosis to create stable attachments between chromosomes and the mitotic spindle (Varma et al., 2012) We also found a new connection between normal cell cycle regulation and protein kinases known as stress-activated MAP kinases (Chandrasekaran et al., 2011). Early on, we discovered the mechanism of Cdc6 ubiquitination and degradation after DNA damage. We identified the ubiquitin ligase responsible for Cdc6 regulation during a DNA damage response (Hall et al., 2007) and a mechanism to restrain rereplication once it begins (Hall et al., 2008). We've also analyzed rereplication in human cells (Dorn et al., 2008), and have described a new cell cycle checkpoint that only works in normal cells but not in cancer cells (Nevis et al. 2009). Follow the link for “Publications” to run an automatic search for all the lab’s papers in PubMed. (Frequent PubMed users will need to click "go" to run the search.)