Microvilli on T cells have been proposed to survey surfaces of antigen-presenting cells (APC) or facilitate adhesion under flow; however, whether they serve essential functions during T cell activation remains unclear. Here we show that antigen-specific T cells deposit membrane particles derived from microvilli onto the surface of cognate antigen-bearing APCs. Microvilli carry T cell receptors (TCR) at all stages of T cell activation and are released as large TCR-enriched, T cell microvilli particles (TMP) in a process of trogocytosis. These microvilli exclusively contain protein arrestin-domain-containing protein 1, which is directly involved in membrane budding and, in combination with vacuolar protein-sorting-associated protein 4, transforms large TMPs into smaller, exosome-sized TMPs. Notably, TMPs from CD4+ T cells are enriched with LFA-2/CD2 and various cytokines involved in activating dendritic cells. Collectively, these results demonstrate that T cell microvilli constitute “immunological synaptosomes” that carry T cell messages to APCs.

FBI-1 (also called Pokemon/ZBTB7A) is a BTB/POZ-domainKrüppel-like zinc-finger transcription factor. Recently, FBI-1 was characterized as a proto-oncogenic protein, which represses tumor suppressor ARF gene transcription. The expression of FBI-1 is increased in many cancer tissues. We found that FBI-1 potently represses transcription of the Rb gene, a tumor suppressor gene important in cell cycle arrest. FBI-1 binds to four GC-rich promoter elements (FREs) located at bp ؊308 to ؊188 of the Rb promoter region. The Rb promoter also contains two Sp1 binding sites: GC-box 1 (bp ؊65 to ؊56) and GC-box 2 (bp ؊18 to ؊9), the latter of which is also bound by FBI-1. We found that FRE3 (bp ؊244 to ؊236) is also a Sp1 binding element. The importance of the tumor suppressor retinoblastoma (Rb) 3 protein in regulating key cellular events was first suggested by the identification of a tumor, retinoblastoma, in which the Rb locus was invariably deleted (1-3). Rb is implicated in the development of various cancers (4 and references therein). Rb suppresses tumorigenesis by inhibiting cell cycle progression at G 1 /S by preventing the transcription of several genes important in cell cycle control (5). Rb is phosphorylated in a cell cycle-dependent manner (6 and references therein). When Rb is hypophosphorylated, it forms complexes with E2F family proteins and inhibits transcription by recruiting proteins involved in transcriptional repression (7). Once phosphorylated, Rb can no longer form complexes with E2F proteins. E2F proteins, upon dimerization with their differentiation-regulated transcription factor partners, are capable of activating the expression of a number of genes that are likely to regulate or promote entry into S phase (6 and references therein). FBI-1 represses transcription of theInvestigations on how transcription of the Rb gene is regulated are important in elucidating the cellular regulatory mechanism of Rb gene expression (8 -12). For example, induction of Rb gene transcription by MyoD, via CREB, is a key event in muscle differentiation (9). Furthermore, transcriptional activation of the Rb gene by GABP and HCF-1 is also important in muscle differentiation (10, 11). In contrast, YY1 and MIZF repress transcription of Rb, and this repression is important for inhibiting myogenesis (10, 12). All these data suggest that multiple transcription factors act on the transcriptional regulation of Rb gene.We have been investigating the biological functions of FBI-1 (also called Pokemon/ZBTB7A), which contains a BTB/POZdomain at its N terminus and Krüppel-like zinc fingers at its C terminus (13,14). Recently, there have been several reports on the function of FBI-1. FBI-1 stimulates the Tat activity of human immunodeficiency virus, type 1 long terminal repeat and represses human ADH5/FDH gene expression by interacting with Sp1 zinc fingers (14, 15). The mouse counterpart of FBI-1, LRF, co-immunoprecipitates and co-localizes with Bcl-6, and is involved in chondrogenesis and adipogenesis (16 -18). The rat homolog of FBI-1...

We found that ZBTB2, a POK family transcription factor, is a potent repressor of the ARF-HDM2-p53-p21 pathway important in cell cycle regulation. ZBTB2 repressed transcription of the ARF, p53, and p21 genes, but activated the HDM2 gene. In particular, ZBTB2 repressed transcription of the p21 gene by acting on the two distal p53 binding elements and the proximal Sp1 binding GC-box 5/6 elements. ZBTB2 directly interacted with Sp1 via its POZ domain and zinc fingers, which was important in the repression of transcription activation by Sp1. ZBTB2 and Sp1 competed with each other in binding to the GC-box 5/6 elements and the two p53 binding elements. ZBTB2 directly interacted with p53 via its zinc fingers, inhibiting p53 binding and repressing transcription activation by p53. The POZ domain, required for transcription repression, interacted with corepressors such as BCoR, NCoR, and SMRT. The interactions deacetylated histones Ac-H3 and -H4 at the proximal promoter. Although ectopic ZBTB2 stimulated cell proliferation, knockdown of ZBTB2 expression decreased cell proliferation and DNA synthesis. Overall, our data suggest that ZBTB2 is a potential proto-oncogenic master control gene of the p53 pathway and, in particular, is a potent transcription repressor of the cell cycle arrest gene p21 by inhibiting p53 and Sp1.The POZ domain is an evolutionarily conserved proteinprotein interaction motif found in many cellular regulatory proteins (1, 2). POZ domain genes, first identified in Drosophila and poxvirus, have since been found in organisms ranging from yeast to humans (3, 4). As many as 184 known human proteins, 96 Drosophila proteins, and 137 Caenorhabditis elegans proteins are estimated to contain the POZ domain.POZ domain proteins are involved in many critical cellular processes such as apoptosis (5), development (6, 7), ion channel activity (4), oncogenesis (8 -10), and transcription (10 -16). In particular, some of the POZ domain Krüppel-like zinc finger (POK) 3 proteins are the major determinants of development, differentiation, and oncogenesis. PLZF-null mice display severe defects in limb development and germ stem cell maintenance (7, 17). T helper-inducing POZ/Krüppel-like factor (Th-POK/cKrox) has been recently reported as a master regulator of T-cell lineage commitment (18). BCL-6, PLZF, and HIC1 have been implicated in non-Hodgkin lymphoma, acute promyelocytic leukemia, and spontaneous malignant tumors, respectively (8,9,19). Recently, FBI-1 (also called Pokemon) has been shown to act as a proto-oncogene by repressing transcription of the ARF gene, causing down-regulation of p53 and promoting oncogenic cellular transformation (10).The most striking property of some POZ domain transcription factors is their ability to repress transcription via their POZ domains (10 -16, 20), although a few POZ domain transcription factors activate transcription (21,22). This characteristic probably underlies many biological processes controlled by these factors. The ability of the domain to interact with key regulatory protei...

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Colorectal cancer (CRC) is among the leading causes of cancer-related death in the world. The development of CRC is associated with smoking, diet, and microbial exposure. Previous studies have shown that dysbiosis of the gut microbiome affects cancer development, because it leads to inflammation and genotoxicity. Supplementation with specific microbiota induces anti-tumor effects by enhancing of anti-tumor immunity. Here, we observed that supplementation with either of two B. breve strains reduces tumor growth in MC38 colon carcinoma-bearing mice. Interestingly, only one B. breve strain boosted the efficacy of cancer therapeutics, including oxaliplatin and PD-1 blockade. Extensive immune profiling and transcriptomic analysis revealed that the boosting B. breve strain augments lymphocyte-mediated anti-cancer immunity. Our results suggest that supplementation with B. breve strains could potentially be used as a strategy to enhance the efficacy of CRC therapeutics.