A temperature-sensitive defect of enterovirus 70 is located at the uridylylation of the genome-linked protein VPg in vitro

Direct involvement of p53 in the base excision repair pathway of the DNA repair machinery

The p53 tumor suppressor that plays a central role in the cellular response to genotoxic stress was suggested to be associated with the DNA repair machinery which mostly involves nucleotide excision repair (NER). In the present study we show for the first time that p53 is also directly involved in base excision repair (BER). These experiments were performed with p53 temperature-sensitive (ts) mutants that were previously studied in in vivo experimental models. We report here that p53 ts mutants can also acquire wild-type activity under in vitro conditions. Using ts mutants of murine and human origin, it was observed that cell extracts overexpressing p53 exhibited an augmented BER activity measured in an in vitro assay. Depletion of p53 from the nuclear extracts abolished this enhanced activity. Together, this suggests that p53 is involved in more than one DNA repair pathway.

Comparison of the ability of lactate dehydrogenase-elevating virus and its virion RNA to infect murine leukemia virus-infected or -uninfected cell lines

Lactate dehydrogenase-elevating virus (LDV) has a strict species specificity. Cells or cell lines other than a particular subset of mouse primary macrophages which can support LDV replication in vitro have not been identified. LDV induces neurological disorders in old C58 or AKR strains, in which the involvement of multiple copies of the endogenous N-tropic murine leukemia virus (MuLV) genome and the Fv-1 locus of the mouse has been implicated. Our previous studies have demonstrated that LDV could infect and replicate in cell lines of the mouse or other species in vitro when they were infected with MuLV. The significance of and the precise mechanism underlying this phenomenon, however, remain unclear. We demonstrated in this study the efficient infection and replication of the virus in vitro by inoculation of its RNA mixed with liposome. No significant difference either in the efficiency of RNA transfection or in the ability to support its replication was observed among the various species' cell lines examined. In addition, by RNA transfection the virus replicated with equal efficiency in MuLV-infected and -uninfected cells or in macrophages derived from mice irrespective of their age. In contrast, the pattern of the infection by virus particles was quite different; LDV replication was observed only in macrophages (particularly from newborn mice) and MuLV-infected cells. By using various LDV isolates, it was demonstrated that the capability of replication between neurovirulent, LDV type C, and the other avirulent strains was almost the same in mouse cell lines when their RNA was introduced into the cells. Higher infectivity of LDV-C to MuLV-infected cells may be due to its efficient incorporation of the particles into MuLV-infected cells.