Genome Integrity Discussion Group (1)
Monday, November 6, 2006
Presented by the Genome Integrity Discussion Group
- 2:00 pm Mike O'Donnell, Rockefeller University - Structure of a sliding clamp-DNA cocrystal and its corresponding C-family DNA polymerase
- 2:30 pm Leemor Joshua-Tor, Cold Spring Harbor Laboratory - DNA Translocation in a Replicative Hexameric Helicase
- 3:00 pm David Spector, Cold Spring Harbor Laboratory - Insights into the Transmission of the "Histone Code"
- 3:30 pm Coffee Break
- 4:00 pm Tom Kelly, Memorial Sloan Kettering Cancer - DNA replication and the DNA damage checkpoint
- 4:30 pm Matthew O'Connell, Mount Sinai School of Medicine - The Smc5/6 complex and DNA damage checkpoint maintenance
- 5:00 pm Nadya Dimitrova, Rockefeller University - MDC1 accelerates non-homologous end joining of dysfunctional telomeres
- 5:20 pm Michelle Sabourin, Princeton University - Telomerase and Tel1p Preferentially Bind Short Telomeres in Yeast
Mike O'Donnell: Structure of a sliding clamp-DNA cocrystal and its corresponding C-family DNA polymerase
Bacterial chromosomal replicases are members of the C-family of DNA polymerases, the last DNA polymerase family to be solved by X-ray crystallography. The recent crystal structure of E. coli α subunit (C-family) DNA polymerase will be presented. The α subunit functions with the ring shaped β sliding clamp, which tethers the enzyme to DNA for exceedingly high processivity. We have recently solved the structure of β bound to DNA. The β-DNA structure and its implications to function during replisome action will be discussed.
Leemor Joshua-Tor: DNA Translocation in a Replicative Hexameric Helicase
The E1 protein of papillomavirus is a replicative hexameric ring helicase belonging to the AAA+ family. Based on structures of the DNA-binding domain of E1 complexes with DNA, we suggested a mechanism for DNA strand separation. However, the mechanism that couples the ATP cycle to DNA translocation has been unclear. I will present the crystal structure of the E1 hexamer with single-stranded DNA discretely bound within the hexamer channel and nucleotides at the subunit interfaces. This structure demonstrates that only one strand of DNA passes through the hexamer channel and that the DNA-binding hairpins of each subunit form a spiral staircase that sequentially tracks the oligonucleotide backbone. Consecutively grouped ATP-, ADP-, and apo- configurations correlate with the height of the hairpin, suggesting a straightforward DNA translocation mechanism. Each subunit sequentially progresses through ATP, ADP, and apo states while the associated DNA-binding hairpin travels from the top staircase position to the bottom, escorting one nucleotide of single-stranded DNA through the channel. These events permute sequentially around the ring from one subunit to the next.
David Spector: Insights into the Transmission of the "Histone Code"
Transmission of the methylation pattern of histone H3 at lysine 9 to daughter cells is an important component of the overall propagation of the epigenetic state of gene activity. We have examined the association and dynamics of euHMTase1 and G9a, the main euchromatin H3K9 specific methyltransferases, in mammalian cells. Our results revealed that these HMTases are both highly dynamic and associate with DNA replication foci throughout S-phase. Data will be discussed to show that the euHMTase1/G9a complex is a crucial determinant for the establishment of the histone H3K9 dimethylation pattern during S-phase.
Matthew O'Connell: The Smc5/6 complex and DNA damage checkpoint maintenance
Eukaryotic cells contain three Structural Maintenance of Chromosomes (SMC) complexes that are