Reconstitution of nucleosomes in vitro with a plasmid carrying the long terminal repeat of Moloney murine leukemia virus

The transactivating effect of HSV-1 ICP0 is enhanced by its interaction with the PCAF component of histone acetyltransferase

ICP0 is a multifunctional protein that plays diverse roles in herpes simplex virus type 1 (HSV-1) infection. It can promote the lytic replication of HSV-1 and activate a variety of viral or cellular genes when introduced into cells by transfection or infection. However, the exact mechanism of ICP0 action is not fully understood. In the present study, we observed the co-localization of ICP0 and PCAF (P300/CBP-associated factor), a component of histone acetyltransferase (HAT), in the ND10 (nuclear dot 10) nuclear body. We further confirmed the interaction between ICP0 and PCAF via yeast two-hybrid assay, co-immunoprecipitation, and histone acetyltransferase assays. Analysis of the functional significance of this interaction suggested that PCAF improved the ability of ICP0 to activate transcription of viral genes. Using chromatin immunoprecipitation (ChIP) assays, we observed ICP0-enhanced histone acetylation levels in both viral and cellular gene promoters. Our study suggests that ICP0 regulates transcription through specific interaction with PCAF.

Integrase-mediated nonviral gene transfection with enhanced integration efficiency

Retroviruses efficiently integrate their genome into the host chromosome. Two elements of the retrovirus genome are needed for the integration: long terminal repeats (LTRs) and integrase protein. We attempted to incorporate the retrovirus integration machinery in lipid vesicle-mediated gene transfection with the aim of achieving efficient stable transfection in a nonviral gene transfection system. A DNA fragment, in which a neomycin-resistant gene was flanked between partial LTR sequences derived from the Rous sarcoma virus (RSV), was constructed. This DNA fragment was transfected together with purified recombinant RSV integrase or integrase expression vectors by means of lipid vesicle-mediated gene transfection. The integrase-mediated transfection enhanced the stable transfection efficiency. The length and the end structure of the LTR sequences were important in achieving high efficiency. Under optimal conditions, the stable transfection efficiency showed a 16-fold improvement over that without integrase.

Methylation strongly enhances DNA bending in the replication origin region of the Escherichia coli chromosome

Two-dimensional gel electrophoresis, at high and low temperatures, and gel mobilities of circularly permuted DNA segments showed a large bending locus about 50 bp downstream from the right border of the 245 bp oriC box, a minimal essential region of autonomous replication on the Escherichia coli chromosome. Bending was strongly enhanced by Dam methylation. In DNA from a Dam- strain, the mobility anomaly arising from altered conformation was much reduced, but was raised to the original level by methylation in vivo or in vitro. Enhancement of the mobility anomaly was also observed by hybrid formation of the Dam- strand with the Dam+ strand. Near the bending center, GATC, the target of Dam methylase, occurs seven times arranged essentially on the same face of the helix with 10.5 bp per turn. We concluded that small bends at each Dam site added up to the large bending detectable by gel electrophoresis.