Natural killer (NK) cells and dendritic cells (DCs) are, respectively, central components of innate and adaptive immune responses. We describe here a third DC lineage, termed interferon-producing killer DCs (IKDCs), distinct from conventional DCs and plasmacytoid DCs and with the molecular expression profile of both NK cells and DCs. They produce substantial amounts of type I interferons (IFN) and interleukin (IL)-12 or IFN-gamma, depending on activation stimuli. Upon stimulation with CpG oligodeoxynucleotides, ligands for Toll-like receptor (TLR)-9, IKDCs kill typical NK target cells using NK-activating receptors. Their cytolytic capacity subsequently diminishes, associated with the loss of NKG2D receptor (also known as Klrk1) and its adaptors, Dap10 and Dap12. As cytotoxicity is lost, DC-like antigen-presenting activity is gained, associated with upregulation of surface major histocompatibility complex class II (MHC II) and costimulatory molecules, which formally distinguish them from classical NK cells. In vivo, splenic IKDCs preferentially show NK function and, upon systemic infection, migrate to lymph nodes, where they primarily show antigen-presenting cell activity. By virtue of their capacity to kill target cells, followed by antigen presentation, IKDCs provide a link between innate and adaptive immunity.

From transcription to translation, mRNA is complexed with heterogeneous nuclear ribonucleoproteins (hnRNP proteins) that mediate mRNA processing, export from the nucleus, and delivery into the cytoplasm. Although the mechanism is unknown, export of mature mRNA from the nucleus is a critical regulatory step in gene expression. Analyses of hnRNP proteins have shown that many of these proteins are required for this essential cellular process. In this study, we characterize the Saccharomyces cerevisiae Nab2 protein, which was first identified as a poly(A) RNA-binding protein (Anderson, J. T., Wilson, S. M., Datar, K. V., and Swanson, M. S. (1993) Mol. Cell. Biol. 13, 2730 -2741). Our work indicates that poly(A) RNA export from the nucleus is dependent upon a functional Nab2 protein; correspondingly, export of Nab2p from the nucleus is dependent upon ongoing RNA polymerase II transcription. Furthermore, we show that Nab2p is modified within its RGG domain by the type I protein-arginine methyltransferase, Hmt1p. Our experiments demonstrate that arginine methylation is required for the export of Nab2p from the nucleus and therefore establish an in vivo effect of this modification. Overall, these experiments provide evidence that Nab2p is an hnRNP protein that is required for poly(A) RNA export and whose export from the nucleus is regulated by Hmt1p.The evolutionary divergence of prokaryotes and eukaryotes also marks the evolution of compartmentalization of the genetic material in the form of a membrane-bound nucleus. In eukaryotes, movement of macromolecules (i.e. proteins and RNA) between the nucleus and the cytoplasm occurs through the nuclear pore complex, which is embedded within the nuclear envelope (1, 2). The presence of the nucleus also compartmentalizes the nuclear transcriptional machinery from the cytoplasmic translational machinery. mRNA serves as the linker molecule between these two cellular processes.Active genes are first transcribed to pre-mRNA via RNA polymerase II and then processed within the nucleus to form mature mRNA transcripts (3). These processing events occur co-transcriptionally and include the addition of a 5Ј 7-methylguanosine cap (4), the splicing of introns (5), and cleavage of the 3Ј end followed by polyadenylation (4, 6). Fully processed transcripts are then exported from the nucleus to the cytoplasm where they can be translated into functional proteins at ribosomes (7,8). Export of mRNA from the nucleus serves as an essential checkpoint in the regulation of gene expression. However, the detailed mechanism of the export of mature mRNA transcripts from the nucleus is poorly understood.From transcription to translation, mRNA is bound by various heterogeneous nuclear ribonucleoproteins (hnRNPs) 1 that serve to regulate the mRNA life cycle (9). Approximately 30 human hnRNP proteins have been identified that have been implicated in various stages of mRNA processing and export (10). Some of these hnRNP proteins shuttle between the nucleus and the cytoplasm (11). They are first imported int...

B7-DC, one of the recently described B7 family members, has the capacity to inhibit T cell responses via engagement of the immunoreceptor tyrosine-based inhibitory motif–containing inhibitory PD-1 receptor as well as enhance responses via an as yet unidentified costimulatory receptor. B7-DC is highly homologous to a coinhibitory B7 family member, B7-H1, which also binds PD-1. It is currently unclear which B7-DC function—costimulation or inhibition—predominates in vivo. To study in vivo functions of B7-DC, we evaluated immune responses in B7-DC knockout (KO) mice. Although not eliminated, interferon-γ (IFN-γ) production by CD4 T cells and IFN-γ–dependent humoral responses were reduced in B7-DC KO mice relative to wild type mice. Antigen-specific CD8 T cell responses and cytotoxic T lymphocyte (CTL) activity were also diminished in B7-DC KO mice. Hepatic tumors grew more quickly in B7-DC KO mice, associated with a decrease in intrahepatic tumor-specific CD8 T cells. These results highlight the contrasting in vivo roles of B7-DC and B7-H1 and indicate that B7-DC functions as a tuning molecule, selectively augmenting T helper 1 and CTL responses.

Mature poly(A) RNA transcripts are exported from the nucleus in complex with heterogeneous nuclear ribonucleoproteins (hnRNPs). Nab2p is an essential Saccharomyces cerevisiae hnRNP protein that interacts with poly(A) RNA and shuttles between the nucleus and cytoplasm. Functional Nab2p is required for export of poly(A) RNA from the nucleus. The Nab2 protein consists of the following four domains: a unique N-terminal domain, a glutamine-rich domain, an arginine-glycine (RGG) domain, and a zinc finger domain. We generated Nab2p deletion mutants to analyze the contribution of each domain to the in vivo function of Nab2p. We first tested whether the deletion mutants could replace the essential NAB2 gene. We then examined the impact of these mutations on Nab2p localization, poly(A) RNA localization, and association of Nab2p with poly(A) RNA. Our analyses revealed that the N-terminal domain is required for nuclear export of both poly(A) RNA and Nab2p. We confirm that the RGG domain is important for Nab2p import in vivo. Finally, the zinc finger domain is critical for the interaction between Nab2p and poly(A) RNA in vivo. Our data support a model where Nab2p associates with poly(A) RNA in the nucleus through the zinc finger domain and facilitates the export of the poly(A) RNA through protein interactions mediated by the N-terminal domain.The eukaryotic cell is divided into functional compartments that separate important cellular processes. This compartmentalization prevents cross-talk between these cellular processes in an inappropriate or unregulated manner. For example, the membrane-bound nucleus serves at least two critical purposes: to sequester and protect the genetic material and to separate the nuclear processes of transcription and pre-mRNA processing from protein translation in the cytoplasm. As a result of this sequestration, the eukaryotic cell has evolved highly regulated mechanisms to actively transport macromolecules into and out of the nucleus (1, 2). Proteins that function within the nucleus are imported through large proteinaceous nuclear pore complexes that are embedded within the nuclear envelope (3). Similarly, macromolecules, including mRNP 1 complexes, consisting of mRNA and hnRNP proteins, are exported from the nucleus through nuclear pores (4).Mature, fully processed mRNAs are selectively exported from the nucleus (4 -6). Thus, nuclear export of poly(A) RNA is extremely complex because it depends on numerous pre-mRNA processing events that must be completed within the nucleus prior to export (6). Nascent transcripts are co-transcriptionally modified by proteins that mediate 5Ј-capping (7), 3Ј-cleavage, polyadenylation (7,8), and splicing (9). During pre-mRNA processing, the maturing mRNAs associate with many heterogeneous nuclear ribonucleoproteins (hnRNPs) (4), which may serve as markers for the completion of pre-mRNA processing events (5). Successful completion of these processing steps results in a mature mRNA species that is ready to be exported from the nucleus to the cytoplasm where it can ...

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A multi-institutional study led by Memorial Sloan-Kettering Cancer Center (MSKCC) shows that patients whose colorectal cancer has spread to the liver and who received chemotherapy directly to the liver through a pump in the abdomen (an approach called Hepatic Arterial Infusion or HAI) fare better than those who received systemic (intravenously administered) chemotherapy. The study was published online in the February 27, 2006, issue of the Journal of Clinical Oncology. "This study demonstrates that HAI therapy extends survival and improves quality of life in patients with colorectal cancer that has spread to the liver," said the study's lead author Nancy E. Kemeny, M.D., medical oncologist in the Department of Medicine at MSKCC. "These positive findings are particularly important, given that metastasis to the liver occurs in 60 percent of patients with metastatic colorectal cancer, and most patients with these liver tumors eventually die of their disease." Several smaller studies have previously compared outcomes of HAI with systemic chemotherapy, but this is the first large study that had no crossover between the groups, meaning that none of the patients in the systemic group received HAI therapy. The study included 135 patients who were assigned randomly to receive either HAI or systemic chemotherapy. All of the patients underwent surgical removal of their primary tumors in the colon or rectum before beginning chemotherapy. Patients receiving HAI then underwent a surgical procedure to have a chemotherapy pump inserted into the abdomen. This procedure can sometimes be done using a minimally invasive laparoscope. Researchers found that patients receiving HAI lived longer than those receiving systemic chemotherapy, with a median survival of 24 versus 20 months. In addition, patients receiving HAI had better response rates (47% versus 24%) and longer time to disease progression in the liver (9.8 months versus 7.3 months). Patients receiving HAI did not experience the usual side effects associated with systemic therapy such as diarrhea, decreased white blood cell counts, and hair loss. However, because patients on the HAI regimen experienced mild toxicity to the liver, their liver function was monitored closely throughout the duration of treatment to prevent the toxicity from becoming more severe. The research began in 1996, before chemotherapy drugs such as irinotecan and oxaliplatin were available, so both sets of patients received the standard drugs at the time, fluorouracil and leucovorin, and had access to the newer drugs as they became available. According to Dr. Kemeny, studies are currently underway at MSKCC using HAI therapy in combination with newer drugs, and response rates appear to be even higher. Furthermore, the addition of HAI therapy is also being investigated in patients with primary liver cancer. The multi-institutional trial was conducted by researchers from the Cancer and Leukemia Group B and the Eastern Cooperative Oncology Group.