Heterochromatin and the DNA damage response: the need to relax.

Higher order chromatin structure has an impact on all nuclear functions, including the DNA damage response. Over the past several years, it has become increasingly clear that heterochromatin and euchromatin represent separate entities with respect to both damage sensitivity and repair. The chromatin compaction present in heterochromatin helps to protect this DNA from damage; however, when lesions do occur, the compaction restricts the ability of DNA damage response proteins to access the site, as evidenced by its ability to block the expansion of H2AX phosphorylation.

Regulation of the cellular DNA double-strand break response.

DNA double-strand breaks occur frequently in cycling cells, and are also induced by exogenous sources, including ionizing radiation. Cells have developed integrated double-strand break response pathways to cope with these lesions, including pathways that initiate DNA repair (either via homologous recombination or nonhomologous end joining), the cell-cycle checkpoints (G1-S, intra-S phase, and G2-M) that provide time for repair, and apoptosis. However, before any of these pathways can be activated, the damage must first be recognized.

Absence of an immediate G1/S checkpoint in primary MEFs following gamma-irradiation identifies a novel checkpoint switch.

DNA double-strand breaks caused by ionizing radiation have been shown to induce G(1)/S, intra-S-phase, and G(2)/M cell cycle checkpoints. However, analysis of the immediate induction of G(1)/S checkpoint at a cellular level has been hampered by the inability to distinguish cells that were already replicating DNA at the time of damage from cells that entered S phase following the DNA damage. We have developed a novel strategy for assessing the initiation of the G(1)/S checkpoint following gamma-irradiation within asynchronous, low passage, primary mouse embryonic fibroblast cultures (MEFs) using a staggered CldU/IdU double-labeling protocol.

TLS, EWS and TAF15: a model for transcriptional integration of gene expression.

Multifunctional proteins are demonstrating that gene expression is not a series of compartmentalized events beginning with transcription and culminating in delivery of mature mRNA into the cytoplasm, but an integrated pathway of transcription, splicing, RNA metabolism and subcellular targeting of translation. One such multifunctional family is made up of the RNA-binding proteins TLS, EWS and TAF15. These three proteins each contribute a potent transcriptional activation domain to oncogenic fusion proteins, and the formation of these fusion genes are thought to be the primary causes of their associated cancers.

Anti-tumor chemotherapy utilizing peptide-based approaches--apoptotic pathways, kinases, and proteasome as targets.

The pharmacological sciences are taking advantage of recent discoveries that have defined the molecular pathways governing apoptosis. These signaling cascades are frequently inactivated or distorted by mutations in cancer cells. Peptides derived from critical interaction, phosphorylation, or cleavage sites are the preferred leads (starting points) for the development of new drugs.