In Parkinson's disease (PD), the oscillatory activity recorded from the basal ganglia shows dopamine-dependent changes. In the "off" parkinsonian motor state, there is prominent activity in the beta band (12-30 Hz) that is mostly attenuated after dopaminergic therapy ("on" medication state). The on state is also characterized by activity in the gamma (60 -80 Hz) and high-frequency (300 Hz) bands that is modulated by movement. We recorded local field potentials from a group of 15 PD patients (three females) treated with bilateral deep brain stimulation of the subthalamic nucleus, using a high sampling rate (2 kHz) and filters suitable to study high-frequency activity (0.3-1000 Hz). We observed high-frequency oscillations (HFOs) in both the off and on motor states. In the off state, the amplitude of the HFOs was coupled to the phase of the abnormal beta activity. The beta-coupled HFOs showed little or even negative movement-related changes in amplitude. Moreover, the degree of movement-related modulation of the HFOs correlated negatively with the rigidity/ bradykinesia scores. In the on motor state, the HFOs were liberated from this beta coupling, and they displayed marked movementrelated amplitude modulation. Cross-frequency interactions between the phase of slow activities and the amplitude of fast frequencies have been attributed an important role in information processing in cortical structures. Our findings suggest that nonlinear coupling between frequencies may not only be a physiological mechanism (as shown previously) but also that it may participate in the pathophysiology of parkinsonism.

bViruses employ a variety of strategies to usurp and control cellular activities through the orchestrated recruitment of macromolecules to specific cytoplasmic or nuclear compartments. Formation of such specialized virus-induced cellular microenvironments, which have been termed viroplasms, virus factories, or virus replication centers, complexes, or compartments, depends on molecular interactions between viral and cellular factors that participate in viral genome expression and replication and are in some cases associated with sites of virion assembly. These virus-induced compartments function not only to recruit and concentrate factors required for essential steps of the viral replication cycle but also to control the cellular mechanisms of antiviral defense. In this review, we summarize characteristic features of viral replication compartments from different virus families and discuss similarities in the viral and cellular activities that are associated with their assembly and the functions they facilitate for viral replication.

The human subgroup C adenoviral E1B 55-kDa protein cooperates with the viral E4 Orf6 protein to induce selective export of viral, late mRNAs from the nucleus to the cytoplasm. Previous studies have suggested that such preferential transport of viral mRNA and the concomitant inhibition of export of cellular mRNAs are the result of viral colonization of specialized microenvironments within the nucleus. However, neither the molecular basis of this phenomenon nor the mechanism by which the E1B 55-kDa protein acts has been elucidated. We therefore examined viral late mRNA metabolism in HeLa cells infected with a series of mutant viruses that carry insertions at various positions in the E1B protein coding sequence (P. R. Yew, C. C. Kao, and A. J. Berk, Virology 179:795-805, 1990). All the mutations examined impaired cytoplasmic accumulation of viral L2 mRNAs and reduced L2 mRNA export efficiency. However, in most cases these defects could be ascribed to reduced E1B 55-kDa protein concentration or the unexpected failure of the altered E1B proteins to enter the nucleus efficiently. The latter property, the pleiotropic defects associated with all the mutations that impaired nuclear entry of the E1B protein, and consideration of its primary sequence suggest that these insertions result in misfolding of the protein. Insertion of four amino acids at residue 143 also inhibited viral mRNA export but resulted in increased rather than decreased accumulation of the E1B 55-kDa protein in the nucleus. This mutation specifically impaired the previously described association of the E1B Human subgroup C adenoviruses, such as adenovirus type 2 (Ad2) and Ad5, encode several proteins that exhibit transforming activity, because they disrupt host cell circuits regulating cell proliferation (33, 63). These gene products include the E1B 55-kDa protein, which can cooperate with E1A proteins in stable transformation of rodent cells and is required for efficient viral replication in permissive human cells (2,50,76). The former function has been ascribed to modulation of the activity and concentration of the cellular p53 protein, a sequence-specific transcriptional activator that induces cell cycle arrest or apoptosis in response to genotoxic and other forms of stress (36, 42). The E1B 55-kDa protein inhibits p53-dependent transcription by binding to the N-terminal activation domain of the cellular protein (34, 61, 80). The E1B protein can function as a general repressor of RNA polymerase II transcription (44, 80). It is therefore believed to inhibit p53-dependent transcription as a result of binding to promoter-associated p53 protein (44). Such transcriptional repression by the E1B protein correlates closely with its transforming activity (80). Indeed, phosphorylation of C-terminal serine (490 and 491) and threonine (495) residues is necessary for transcriptional repression, transformation, and inhibition of p53-dependent apoptosis induced by the viral 243R E1A protein (68), indicating that repression of p53-dependent transcription is importa...

Rotavirus NSP5 is a non-structural phosphoprotein with putative autocatalytic kinase activity, and is present in infected cells as various isoforms having molecular masses of 26, 28 and 30-34 kDa. We have previously shown that NSP5 forms oligomers and interacts with NSP6 in yeast cells. Here we have mapped the domains of NSP5 responsible for these associations. Deletion mutants of the rotavirus YM NSP5 were constructed and assayed for their ability to interact with full-length NSP5 and NSP6 using the yeast two-hybrid assay. The homomultimerization domain was mapped to the 20 C-terminal aa of the protein, which have a predicted α-helical structure. A deletion mutant lacking the 10 C-terminal aa (∆C10) failed to multimerize both in yeast cells and in an in vitro affinity assay. When transiently expressed in MA104 cells, NSP5 became hyperphosphorylated (30-34 kDa isoforms). In contrast, the ∆C10 mutant produced forms equivalent to the 26 and 28 kDa species, but was poorly hyperphosphorylated, suggesting that multimerization is important for this proposed activity of the protein. The interaction domain with NSP6 was found to be present in the 35 C-terminal aa of NSP5, overlapping the multimerization domain of the protein, and suggesting that NSP6 might have a regulatory role in the self-association of NSP5. NSP6 was also found to interact with wild-type NSP5, but not with its mutant ∆C10, in cells transiently transfected with plasmids encoding these proteins, confirming the relevance of the 10 C-terminal aa for the formation of the heterocomplex.

The human adenovirus type 5 (Ad5) E1B 55-kDa protein is required for selective nuclear export of viral late mRNAs from the nucleus and concomitant inhibition of export of cellular mRNAs in HeLa cells and some other human cell lines, but its contributions(s) to replication in normal human cells is not well understood. We have therefore examined the phenotypes exhibited by viruses carrying mutations in the E1B 55-kDa protein coding sequence in normal human fibroblast (HFFs). Ad5 replicated significantly more slowly in HFFs than it does in tumor cells, a difference that is the result of delayed entry into the late phase of infection. The A143 mutation, which specifically impaired export of viral late mRNAs from the nucleus in infected HeLa cells (R. During the late phase of human adenovirus type 5 (Ad5) infection, cellular protein synthesis is severely inhibited, while viral late proteins are made in large quantities (3, 6). Such preferential expression of viral genes is the result of posttranscriptional regulatory mechanisms: several viral gene products, including VA-RNA1 and the L4 100-kDa protein, contribute to selective translation of viral late mRNAs (see references 18, 64, and 85 for reviews), while the E1B 55-kDa and E4 Orf 6 proteins induce selective export of these mRNAs from the nucleus (reviewed in references 25, 33, and 39). In infected cells, these last two early proteins form a complex (84) that has been implicated in regulation of mRNA export (12, 19). Indeed, the E1B 55-kDa and E4 Orf 6 proteins colocalize to specific sites within infected cell nuclei, the peripheral zones of replication centers (70). Transcription of viral late genes and at least initial processing of viral pre-mRNAs take place at these same sites (4,14,74,75). Mutations that prevent synthesis of the E4 Orf 6 protein or reduce binding of this to the E1B 55-kDa protein (83) result in both mislocalization of the E1B 55-kDa protein and defects in export of viral late mRNAs (39, 70). These properties indicate that E4 Orf 6 protein-dependent recruitment of the E1B protein to the specialized nuclear sites at which viral late pre-mRNAs are synthesized promotes selective export of the processed mRNAs. The observation that the accumulation of viral mRNAs at enlarged interchromatin granules, which form in infected cells as the late phase progresses, correlates with efficient late mRNA export (4, 13) provides further support for the view that efficient mRNA export is intimately coupled to the organization of infected cell nuclei. However, the molecular basis of such coupling remains unknown, nor has the cellular export pathway by which viral late mRNAs are transported from the nucleus to the cytoplasm been identified.AThe E1B 55-kDa protein contains a leucine-rich nuclear export signal (NES) that is recognized by the cellular exportin 1 export receptor and mediates shuttling of the viral protein when it is synthesized either alone or in Ad5-infected cells (26,58). It has also been reported that the E4 Orf 6 protein contains a similar NES nece...