The timing and localization of DNA replication initiation in mammalian cells are heritable traits, but it is not known whether initiation requires specific DNA sequences. A site-specific recombination strategy was used to show that DNA sequences previously identified as replication initiation sites could initiate replication when transferred to new chromosomal locations. An 8-kilobase DNA sequence encompassing the origin of DNA replication in the human beta-globin locus initiated replication in the simian genome. Specific deletions within the globin origin did not initiate replication in these chromosomal sites. These data suggest that initiation of DNA replication in mammalian cells requires specific sequence information and extend the replicon hypothesis to higher eukaryotes.

California sea lions are one of the major marine mammal species along the Pacific coast of North America. Sea lions are susceptible to a wide variety of viruses, some of which can be transmitted to or from terrestrial mammals. Using an unbiased viral metagenomic approach, we surveyed the fecal virome in California sea lions of different ages and health statuses. Averages of 1.6 and 2.5 distinct mammalian viral species were shed by pups and juvenile sea lions, respectively. Previously undescribed mammalian viruses from four RNA virus families (Astroviridae, Picornaviridae, Caliciviridae, and Reoviridae) and one DNA virus family (Parvoviridae) were characterized. The first complete or partial genomes of sapeloviruses, sapoviruses, noroviruses, and bocavirus in marine mammals are reported. Astroviruses and bocaviruses showed the highest prevalence and abundance in California sea lion feces. The diversity of bacteriophages was higher in unweaned sea lion pups than in juveniles and animals in rehabilitation, where the phage community consisted largely of phages related to the family Microviridae. This study increases our understanding of the viral diversity in marine mammals, highlights the high rate of enteric viral infections in these highly social carnivores, and may be used as a baseline viral survey for comparison with samples from California sea lions during unexplained disease outbreaks.California sea lions (Zalophus californianus) have a population of approximately 240,000 and along with seals and walruses are members of the subgroup Pinnipedia in the suborder Caniformia in the order Carnivora. They inhabit mainland shorelines and coastal islands along the west coast of North America and migrate along the coast during the nonbreeding season. California sea lions are strict carnivores, eating a variety of marine prey, including more than 50 species of fishes and cephalopods. Sea lion pups start eating fish at about 5 months of age, in addition to their mother's milk; are weaned at 10 to 12 months old; and can live up to 15 to 25 years. California sea lions are gregarious animals, forming large rookeries at breeding sites, and aggregate at high densities on haul-out sites (7).California sea lions share beaches and coastal waters with humans, often resting on human-made structures such as docks and boats, and are affected by pathogens and chemicals that enter coastal waters through runoff and sewage outfalls (5). Features of California sea lions, including their large population, wide geographic distribution and migration, gregarious nature, long life span, and shared environment with humans, may favor the transmission of viruses among themselves and to and/or from humans and other mammals.A commonly reported sea lion virus is San Miguel sea lion virus (SMSV), a calicivirus in the genus Vesivirus. SMSV was first isolated from California sea lions from San Miguel Island in 1972 (53). SMSV causes vesicular lesions of the skin and mucosa, abortion, pneumonia, and encephalitis in sea lions and is transmissible to sw...

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A defective Epstein-Barr virus (EBV) containing a deleted and rearranged genome (het DNA) causes latent EBV to replicate. This activity maps to the 2. Previous work identified an EBV gene product that switches the virus from latency into replication (12)(13)(14)(15) Fig. 2 legend).Transfection. Stationary-phase cells were exposed for 30 min at 37°C to 1-5 ug of DNA in RPMI medium containing 100 ,ug of DEAE-dextran per ml. Thereafter, cells were washed and resuspended in conditioned growth medium with or without phorbol 12-myristate 13-acetate (PMA) at 4 ng/ml for 48 hr.Polypeptide Detection. ZEBRA was detected by Western blotting with monospecific antibodies raised in rabbits immunized with a TrpE-BZLF1 fusion protein (N.T., J.C., C.R., D. Katz, and G.M., unpublished data). Replicative polypeptides were detected with human WC antiserum (26). RESULTSRearranged Sequences from BamHI W Enhance ZEBRA Expression After Transfection of BL Cells. Countryman et al. had shown that rearranged sequences in WZhet did not contribute to the structural gene for the ZEBRA protein nor were they obligatory for activating EBV replication in a somatic cell hybrid (D98/HR-1) (13). These conclusions were based on the use ofdeletion mutants in which sequences were progressively removed from the BamHI W region of pSV2neo WZhet (Fig. 1 A and B).To determine whether rearranged sequences from BamHI W affected expression of ZEBRA in B cells the same mutants were transfected into BL41/CL16 cells. Expression of ZEBRA was monitored 48 hr after transfection by using monospecific anti-BZLF1 antibody (Fig. 1C) 9801The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.