Whether the protein-DNA interactions described here are important for the function of these proteins in ATR-Chk1 signaling in vivo is not known. Additional experiments are therefore necessary to clarify the importance of these protein-DNA interactions. We conclude from these results that there are many proteinDNA interactions that may be important for association and accumulation of ATR-Chk1 pathway proteins at sites of DNA (+)-JQ1 damage and replication stress. However, we recognize and note that only limited conclusions can be drawn from protein-DNA nteraction studies in the absence of additional methods and approaches. Whether any or all of the checkpoint protein-DNA interactions we described here are biologically relevant to ATRChk1 signaling in vivo clearly requires further investigation. The identification of new protein-DNA interactions should aid this process and lead to a greater understanding of the mechanisms of ATR-Chk1 pathway activation in response to DNA damage and replication stress. Presentation of MHC class I /peptide complexes on the cell surface of antigen presenting cells is crucial first step in the activation of cytotoxic T lymphocyte -mediated antiviral and anti-tumor immune responses. Amongst APCs, activated DCs are by far the most potent for initiating CD8+ T-cell responses; thus, they have held great promise for use in vaccines aimed at eliciting or boosting pathogen- or tumor antigen-specific CTLs. Many studies have reported strong induction of CTL responses following DC-based vaccination in both animal models and in selected clinical trials involving cancer patients and those harboring chronic viral infections. However, although the majority of experimental DC vaccines have been successful at generating antigen-specific CTLs, clinical responses have remained sporadic, underscoring a need to improve the efficacy of DC-based vaccination. A number of studies have demonstrated that the,35 amino acid cytoplasmic tail of MHC-I plays a critical role in intracellular trafficking, DC-mediated antigen presentation and CTL priming. Encoded by two separate exons and containing a number of highly conserved features, it has been shown that deletion of the entire MHC-I cytoplasmic tail results in a complete abrogation of anti-viral CTL responses in vivo. Subsequently, it was shown that a membrane-proximal tyrosine residue encoded by exon 6 forms part of a putative endocytic motif which is required for proper MHC-I trafficking through DC endosomal compartments, cross-presentation of exogenous antigens, and antiviral CTL priming.