Brd4 protein has been proposed to act as a cellular receptor for the bovine papillomavirus type 1 (BPV1) E2 protein in the E2-mediated chromosome attachment and mitotic segregation of viral genomes. Here, we provide data that show the involvement of Brd4 in multiple early functions of the BPV1 life cycle, suggest a Brd4-dependent mechanism for E2-dependent transcription activation, and indicate the role of Brd4 in papillomavirus and polyomavirus replication as well as cell-specific utilization of Brd4-linked features in BPV1 DNA replication. Our data also show the potential therapeutic value of the disruption of the E2-Brd4 interaction for the development of antiviral drugs.Papillomavirus (PV) E2 protein is a central regulator of the viral life cycle. In addition to its well-established activity as a transcription modulator and replication initiator protein (6), E2 of bovine papillomavirus type 1 (BPV1) has recently emerged as a trans factor which mediates mitotic segregation of viral genomes by tethering them to host cell chromatin (7,12,19). The first candidate for a receptor of E2 in the latter process, Brd4, is attached to the chromatin through its two bromodomains, which bind to acetylated histones H3 and H4 both in interphase and in mitosis (4, 25). Mutated E2 proteins that are defective in Brd4 binding are unable to bind to mitotic chromosomes (2), and ectopic expression of Brd4 can reconstitute the BPV1 E2-dependent extrachromosomal plasmid maintenance in the yeast Saccharomyces cerevisiae, where such a process normally does not function (3). Ectopic expression of the E2-binding C-terminal domain (CTD) of Brd4 in mammalian cells disrupts the interaction of E2 with cellular Brd4 and relocates E2 from mitotic chromosomes (25,26). Brd4 CTD binds to the N-terminal domain of E2 (25), which is also responsible for interactions critical for transcription activation and replication initiator activities of E2. Therefore, we suspected that Brd4 might have a more complex role in the PV life cycle than initially proposed. We tested this idea in the present study and show that the Brd4 bromodomain protein can indeed participate in the BPV1 E2-dependent transcription activation and DNA replication processes. Brd4 is specifically involved in the E2-activated transcription process; the role of Brd4 in BPV1 DNA replication, however, is either largely or completely independent of its binding to E2. Our data demonstrate the possible involvement of Brd4 also in polyomavirus DNA replication and reveal the varying importance of the Brd4-linked component for BPV1 DNA replication in different cell lines.Cloning of the dominant-negative form of Brd4 (Brd4 CTD). The use of a dominant-negative truncated version of Brd4 is a useful alternative to manipulations with a full-length gene, as overexpression or knockout of Brd4 in mammalian cells has been shown to cause severe alterations in cell growth (5, 15). Overexpression of Brd4 CTD affects neither the growth of several cell lines (C127, C33A, HeLa) (25, 26) nor the cell cycle dist...

Recent animal studies consistently confirm the involvement of brain-derived neurotrophic factor (BDNF) in the regulation of anxiety-related behaviours. The role of BDNF in human anxiety has been less investigated. The aim of our study was to examine the association between serum BDNF levels and panic/anxiety responses to cholecystokinin-tetrapeptide (CCK-4) challenge in healthy subjects. BDNF concentrations were detected in serum samples of 37 male and female volunteers before and 120 min after CCK-4 injection. The baseline levels of serum BDNF did not predict the occurrence of CCK-4-induced panic attacks or intensity of panic symptoms and did not significantly change 2 h after the challenge. BDNF serum concentrations 120 min after provocation did not differentiate panickers from non-panickers; however, the subjects reporting stronger anxiety response showed higher levels of BDNF than those with mild anxiety. The anxiety net increase on the Visual Analogue Scale, but not severity of panic symptoms, significantly and positively correlated with the change in BDNF concentration from baseline values. This is the first challenge study to demonstrate a possible impact of BDNF on human anxiety. Our findings suggest a general involvement of BDNF in the regulation of anxiety rather than a specific role of BDNF in disposition to panic attacks.